Zirconium alloys (Zircaloy, ZIRLO, Zr-2.5Nb, Zr-Al) Zr alloys
Zr-based alloys. Nominal Zircaloy-4 is Zr-1.5Sn-0.2Fe-0.1Cr (wt %). Zircaloy-2: Zr with Sn 1.20 to 1.70, Fe 0.07 to 0.20, Cr 0.05 to 0.15, Ni 0.03 to 0.08 wt %. Zircaloy-4: Zr with Sn 1.20 to 1.70, Fe 0.18 to 0.24, Cr 0.07 to 0.13 wt %. Zr-2.5Nb: Zr with Nb 2.40 to 2.80 wt %. ZIRLO: Zr with Nb about 1 and Sn 0.7 to 1 wt % (Wikipedia alloy table
Also known as UNS R60802, UNS R60804, UNS R60904, Zircaloy-2, Zircaloy-4, ZIRLO
Zirconium alloys add small amounts of tin, iron, chromium, nickel or niobium to zirconium.
Evidence level
2 of 5
Lab-measured
- 0Predicted only. No one has made it, or no measurement exists.
- 1Calculated. Only calculated or predicted values from sources.
- 2Lab-measured. Measured properties with their conditions stated.
- 3Space-relevant tests. Measured in conditions relevant to space, such as vacuum or atomic oxygen.
- 4Ground-qualified. Qualified for an application on the ground.
- 5Flown or field-proven. Flight or field results exist.
Resist hot acid
0.05 mm/a
Carry heat
21.5 W/m-K
Weight
6.55 g/cc
Tensile strength
541 MPa
Research alloy strength
888 MPa
Recipe, share of the weight
- Zr 95%Zirconium
- Sn 1.2 to 1.7%Tin
- Fe 0.18 to 0.24%Iron
- Cr 0.07 to 0.13%Chromium
- Nb 2.4 to 2.8%Niobium
Best for
Nuclear fuel cladding and reactor pressure tubes, where low thermal neutron absorption (0.22 barns for Zircaloy-4) and corrosion resistance in water and steam both matter (ATI reactor-grade sheet)
Weakest at
Hydride embrittlement: hydrogen from water oxidation forms hydrides that blister and crack the cladding (Wikipedia), and hot hydrochloric acid still attacks Zircaloy-4 at 0.36 mm/a
Risk at a glance
- People None found. No hazard class found
- If it fails High. Delayed hydride cracking of Zircaloy cladding
- Corrosion Moderate. Hot concentrated hydrochloric acid attacks Zircaloy-4 at a measurable rate.
Quick facts: Zr alloys
| Property | Value | Basis |
|---|---|---|
| Density | 6.55 g/cm³ | 1 sourced value |
| Yield strength | 468 to 998 MPa | 3 sourced values across conditions |
| Tensile strength | 515 to 1,069 MPa | 4 sourced values across conditions |
| Young's modulus | 99.3 GPa | 1 sourced value |
| Thermal conductivity | 21.5 W/(m·K) | 1 sourced value |
| Thermal expansion (CTE) | 6 ppm/K | 1 sourced value |
| Melting point | 1,850 °C | 1 sourced value |
| Specific heat | 285 J/(kg·K) | 1 sourced value |
What is the density of Zirconium alloys (Zr alloys)?
Zirconium alloys (Zr alloys) has a density of 6.55 g/cm³. The source and test conditions are listed in the properties table on this page.
What is the thermal conductivity of Zirconium alloys (Zr alloys)?
Zirconium alloys (Zr alloys) has a thermal conductivity of 21.5 W/(m·K). The source and test conditions are listed in the properties table on this page.
What is the coefficient of thermal expansion of Zirconium alloys (Zr alloys)?
Zirconium alloys (Zr alloys) has a coefficient of thermal expansion of 6 ppm/K. The source and test conditions are listed in the properties table on this page.
What is the melting point of Zirconium alloys (Zr alloys)?
Zirconium alloys (Zr alloys) has a melting point of 1,850 °C. The source and test conditions are listed in the properties table on this page.
What is the yield strength of Zirconium alloys (Zr alloys)?
Zirconium alloys (Zr alloys) has a yield strength of 468 to 998 MPa. The range covers 3 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What are the other names and codes for Zirconium alloys (Zr alloys)?
Zirconium alloys (Zr alloys) is also written as UNS R60802, UNS R60804, UNS R60904, Zircaloy-2, Zircaloy-4, ZIRLO. Each code is printed in the source listed beside it in the designations table.
What is Zirconium alloys (Zr alloys) used for?
Uses recorded in the sources include Zircaloy-4 fuel cladding in pressurized water and CANDU reactors; Zircaloy-2 fuel cladding in boiling water reactors and calandria tubing in CANDU reactors; Zr-2.5Nb pressure tubes in CANDU reactors.
Why it exists
Zircaloy-2 and Zircaloy-4 are the workhorse fuel cladding alloys of water reactors. Zircaloy-4 has the same tin content as Zircaloy-2 but more iron and no nickel, which the ATI sheet says reduces hydrogen uptake in certain reactor conditions. Zr-2.5Nb adds niobium for strength and is used for CANDU pressure tubes. ZIRLO, a Westinghouse alloy with about 1 wt % niobium and 0.7 to 1 wt % tin, is used for cladding in boiling and pressurized water reactors. The alloys keep the low thermal neutron cross section of zirconium (0.18 barns) and its corrosion resistance, with Zircaloy-4 at 0.22 barns.
Where it's used
Fuel cladding in pressurized water reactors
ATI says Zircaloy-4 is typically used as fuel cladding in pressurized water reactors and CANDU reactors. Wikipedia lists Zircaloy-4 as cladding and structural components in BWR, PWR and CANDU reactors.
Cladding and calandria tubing in boiling water and CANDU reactors
ATI says Zircaloy-2 has been used mainly as fuel cladding in boiling water reactors and as calandria tubing in CANDU reactors.
Pressure tubes in CANDU reactors
ATI says Zr-2.5Nb has been used for CANDU pressure tubes. Wikipedia adds that a Zr-2.5Nb alloy is formed into a knee or hip implant and then oxidised to give a hard ceramic bearing surface.
ZIRLO cladding (Westinghouse)
The Wikipedia alloy table lists ZIRLO as Westinghouse cladding for BWR and PWR reactors, with 0.7 to 1 wt % Sn and 1 wt % Nb.
Recipe
Zr-based alloys. Nominal Zircaloy-4 is Zr-1.5Sn-0.2Fe-0.1Cr (wt %). Zircaloy-2: Zr with Sn 1.20 to 1.70, Fe 0.07 to 0.20, Cr 0.05 to 0.15, Ni 0.03 to 0.08 wt %. Zircaloy-4: Zr with Sn 1.20 to 1.70, Fe 0.18 to 0.24, Cr 0.07 to 0.13 wt %. Zr-2.5Nb: Zr with Nb 2.40 to 2.80 wt %. ZIRLO: Zr with Nb about 1 and Sn 0.7 to 1 wt % (Wikipedia alloy table; iron level not given there). Zr-Al: research alloys ZrAl14Ti3 and ZrAl14Ti9 (at. %), not a commercial composition.
Zircaloys are zirconium with small additions of tin, iron, chromium and, for Zircaloy-2, nickel. Zircaloy-4 has the nominal composition Zr-1.5Sn-0.2Fe-0.1Cr (ATI; also arXiv). Zr-2.5Nb is zirconium with 2.4 to 2.8 wt % niobium. Most zirconium metal is made by reducing zirconium(IV) chloride with magnesium in the Kroll process (Wikipedia), and the alloy is then melted with its additions.
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Zirconium Zr | 95% | Base metal. Wikipedia says nuclear-grade zirconium alloys are more than 95 weight percent zirconium. |
| Tin Sn | 1.2 to 1.7% | Main alloying element in Zircaloy-2, Zircaloy-4 and ZIRLO; adds strength and helps corrosion resistance (ATI composition table). |
| Iron Fe | 0.18 to 0.24% | Zircaloy-4 addition; Zircaloy-2 has 0.07 to 0.20 wt % (ATI composition table). |
| Chromium Cr | 0.07 to 0.13% | Zircaloy-4 addition; Zircaloy-2 has 0.05 to 0.15 wt % (ATI composition table). |
| Niobium Nb | 2.4 to 2.8% | Zr-2.5Nb binary alloy addition for strength (ATI composition table). ZIRLO has about 1 wt % Nb (Wikipedia). |
Weight shares are as printed in the sources.
What it can do
Resist hot acid
0.05 mm/a
Zircaloy-4 corrodes at 0.05 mm/a in 70 % nitric acid at 120 °C, and under 0.13 mm/a in 70 % sulfuric acid at 150 °C. Hydrochloric acid at 70 % and 160 °C is worse, at 0.36 mm/a.
Carry heat
21.5 W/m-K
measured
Zircaloy-4 conducts heat at 21.5 W/m-K. ATI says zirconium alloys conduct heat better than stainless steel alloys.
Weight
6.55 g/cc
measured
Zircaloy-4 has a density of 6.55 g/cc, and the ATI sheet gives its melting point as 1850 °C.
Tensile strength
541 MPa
measured
Annealed Zircaloy-4 strip has a room-temperature tensile strength of 541 MPa longitudinally and 515 MPa transversely. At 288 °C the longitudinal value falls to 271 MPa.
Research alloy strength
888 MPa
measured
In one open-access paper, the research alloy ZrAl14Ti3 reached an offset yield strength of 888 MPa, and ZrAl14Ti9 reached 998 MPa, with about 23 % fracture elongation for both. These are research alloys with no commercial grade.
How it compares
Zircaloy-4 has a thermal neutron cross section of 0.22 barns, against 0.18 barns for pure zirconium, and a thermal conductivity of 21.5 W/m-K. Zr-Al is a different class: the research alloys reach about 888 to 1069 MPa at room temperature, far above the 541 MPa annealed Zircaloy-4 strip, but no corrosion or thermal data were found for them. Read the rows as grades of one family, not as a ranking that covers every alloy.
The same measurements for each material, so you can compare them. Each row names the key condition under the value; the full conditions and methods are in the numbered notes under Technical details. Other materials are shown beside it; each was measured under its own conditions, so open its page before comparing closely. Compare every grade in the family.
| Measurement | Zr alloys | W | WC | Hf | Mo | Mo-Re | Mo-30W | TZM | Nb | Nb alloys | Re | W-Re | WHA | W-Cu | W-Ag | WT20 | V | V alloys | Zr | TiH2 | Be |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Thermal behavior and safety | |||||||||||||||||||||
| Melting point, Zircaloy-4 | 1850 °C2 | 3695 K | no data | 2233 °C | 2623 °C | > 2610 °C | 2829 °C | no data | 2477 °C | 2350 °C | 3186 °C | 3350 °C | no data | no data | no data | 3695 K | 1910 °C | 1900 °C | 1852 °C | > 400 °C | 1287 °C |
| Thermal conductivity, Zircaloy-4 | 21.5 W/m-K3 | 174 W m-1 K-1 | 110 W/(m·K) | 23 W/(m·K) | 142 W/(m·K) | no data | no data | 130 W/(m·K) | 53.7 W/(m·K) | 38.1 W/(m·K) | 48 W/m·K | no data | no data | 235 W/(m·K) | no data | 174 W m-1 K-1 | 30.7 W/(m·K) | no data | 22 W/(m·K) | no data | 216 W/(m·K) |
| Heat capacity, Zircaloy-4 | 0.285 J/g-°C4 | no data | no data | 25.69 J/(g·K) | 0.25 J/(g·K) | no data | no data | 0.25 J/(g·K) | 264.8 J/(kg·K) | no data | no data | no data | no data | no data | no data | no data | no data | no data | 0.2847 kJ/(kg·K) | no data | 1.95 J/g/°C |
| Thermal neutron cross section, Zircaloy-4 | 0.22 barns17 | no data | no data | 104 barn | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | 0.18 barns | no data | no data |
| Thermal neutron cross section, zirconium | 0.18 barns18 | no data | no data | 104 barn | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | 0.18 barns | no data | no data |
| Physical and electrical | |||||||||||||||||||||
| Density, Zircaloy-4 | 6.55 g/cc1 | 19250 kg/m3 | 14.8 g/cm³ | 13.3 g/cm³ | 10.22 g/cm³ | 14.6 g/cm³ | 10.9 g/cm³ | 10.2 g/cm³ | 8.582 g/cm³ | 8.85 g/cm³ | 21.02 g/cm³ | 19.4 g/cm³ | 16.85 to 17.25 g/cc | 15.15 g/cm³ | 11.75 to 16.1 g/cm³ | 19250 kg m-3 | 6.11 g/cm³ | 6.05 g/cm³ | 6.51 g/cm³ | 3.91 g/cm³ | 1.85 g/cm³ |
| Temperature behavior | |||||||||||||||||||||
| Alpha to alpha plus beta transformation, Zircaloy-4 | 810 °C19 | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data |
| Alpha plus beta to beta transformation, Zircaloy-4 | 980 °C20 | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data |
| Other measurements | |||||||||||||||||||||
| Coefficient of thermal expansion, Zircaloy-4 at 25 degC | 6 µm/(m·°C)5 | 4.5×10^-6 K-1 | 5.5 μm/(m·K) | 5.9 ppm/K | 5.2 ppm/K | no data | no data | 5.3 to 5.7 ppm/K | 7.07 ppm/K | no data | no data | no data | no data | 8.3 ppm/K | no data | no data | 8.3 ppm/K | no data | 6.3 10-6/°C | no data | 11.3 ppm/°C |
| Modulus of elasticity, Zircaloy-4 | 99.3 GPa6 | 411 GPa | 530 to 700 GPa | 137 GPa | no data | no data | no data | 300 GPa | 105 GPa | 90 GPa | 460 GPa | no data | 340 GPa | 280 GPa | no data | 411 GPa | 128 GPa | 125.6 GPa | 99.2 GPa | no data | 290 GPa |
| Shear modulus, Zircaloy-4 | 36.2 GPa7 | 161 GPa | no data | 54.2 GPa | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | no data | 36.2 GPa | no data | no data |
| Poisson's ratio, Zircaloy-4 | 0.37 -8 | 0.28 (no units) | no data | 0.29 - | no data | no data | no data | no data | no data | no data | 0.3 - | no data | no data | no data | no data | no data | 0.36 - | no data | no data | no data | no data |
| Tensile strength, Zircaloy-4 longitudinal, room temperature | 541 MPa9 | no data | no data | > 400 MPa | 411 MPa | 719 MPa | 170 MPa | 800 to 1000 MPa | 386 MPa | 386 MPa | 400 to 700 MPa | 220 x 10^3 psi | 758 MPa | 620 to 689 MPa | no data | no data | no data | 488 MPa | 468.1 MPa | no data | > 290 MPa |
| Tensile strength, Zircaloy-4 transverse, room temperature | 515 MPa10 | no data | no data | > 400 MPa | 411 MPa | 719 MPa | 170 MPa | 800 to 1000 MPa | 386 MPa | 386 MPa | 400 to 700 MPa | 220 x 10^3 psi | 758 MPa | 620 to 689 MPa | no data | no data | no data | 488 MPa | 468.1 MPa | no data | > 290 MPa |
| Tensile strength, Zircaloy-4 longitudinal, 288 degC | 271 MPa11 | no data | no data | > 400 MPa | 411 MPa | 719 MPa | 170 MPa | 800 to 1000 MPa | 386 MPa | 386 MPa | 400 to 700 MPa | 220 x 10^3 psi | 758 MPa | 620 to 689 MPa | no data | no data | no data | 488 MPa | 468.1 MPa | no data | > 290 MPa |
| Tensile strength, Zircaloy-4 transverse, 288 degC | 241 MPa12 | no data | no data | > 400 MPa | 411 MPa | 719 MPa | 170 MPa | 800 to 1000 MPa | 386 MPa | 386 MPa | 400 to 700 MPa | 220 x 10^3 psi | 758 MPa | 620 to 689 MPa | no data | no data | no data | 488 MPa | 468.1 MPa | no data | > 290 MPa |
| Yield strength, Zircaloy-4 transverse, room temperature | 468 MPa13 | no data | no data | > 151 MPa | 265 MPa | 557 MPa | no data | 750 to 900 MPa | 276 MPa | 276 MPa | 200 to 500 MPa | no data | 517 MPa | no data | no data | no data | no data | 402 MPa | 321.1 MPa | no data | > 207 MPa |
| Yield strength, Zircaloy-4 transverse, 288 degC | 170 MPa14 | no data | no data | > 151 MPa | 265 MPa | 557 MPa | no data | 750 to 900 MPa | 276 MPa | 276 MPa | 200 to 500 MPa | no data | 517 MPa | no data | no data | no data | no data | 402 MPa | 321.1 MPa | no data | > 207 MPa |
| Elongation, Zircaloy-4 longitudinal, room temperature | 28 %15 | no data | no data | > 20 % | no data | 18 % | 10 % | 6 to 10 % | 20 % | 20 % | 30 to 50 % | 20 % | 5 % | 8.3 % | no data | no data | 35 % | 30.8 % | 28.9 % | no data | > 3 % |
| Elongation, Zircaloy-4 transverse, room temperature | 29 %16 | no data | no data | > 20 % | no data | 18 % | 10 % | 6 to 10 % | 20 % | 20 % | 30 to 50 % | 20 % | 5 % | 8.3 % | no data | no data | 35 % | 30.8 % | 28.9 % | no data | > 3 % |
| Offset yield strength, ZrAl14Ti3 (research alloy) | 888 MPa21 | no data | no data | > 151 MPa | 265 MPa | 557 MPa | no data | 750 to 900 MPa | 276 MPa | 276 MPa | 200 to 500 MPa | no data | 517 MPa | no data | no data | no data | no data | 402 MPa | 321.1 MPa | no data | > 207 MPa |
| Tensile strength, ZrAl14Ti3 (research alloy) | 1056 MPa22 | no data | no data | > 400 MPa | 411 MPa | 719 MPa | 170 MPa | 800 to 1000 MPa | 386 MPa | 386 MPa | 400 to 700 MPa | 220 x 10^3 psi | 758 MPa | 620 to 689 MPa | no data | no data | no data | 488 MPa | 468.1 MPa | no data | > 290 MPa |
| Fracture elongation, ZrAl14Ti3 (research alloy) | 23 %23 | no data | no data | > 20 % | no data | 18 % | 10 % | 6 to 10 % | 20 % | 20 % | 30 to 50 % | 20 % | 5 % | 8.3 % | no data | no data | 35 % | 30.8 % | 28.9 % | no data | > 3 % |
| Offset yield strength, ZrAl14Ti9 (research alloy) | 998 MPa24 | no data | no data | > 151 MPa | 265 MPa | 557 MPa | no data | 750 to 900 MPa | 276 MPa | 276 MPa | 200 to 500 MPa | no data | 517 MPa | no data | no data | no data | no data | 402 MPa | 321.1 MPa | no data | > 207 MPa |
| Tensile strength, ZrAl14Ti9 (research alloy) | 1069 MPa25 | no data | no data | > 400 MPa | 411 MPa | 719 MPa | 170 MPa | 800 to 1000 MPa | 386 MPa | 386 MPa | 400 to 700 MPa | 220 x 10^3 psi | 758 MPa | 620 to 689 MPa | no data | no data | no data | 488 MPa | 468.1 MPa | no data | > 290 MPa |
| Fracture elongation, ZrAl14Ti9 (research alloy) | 23 %26 | no data | no data | > 20 % | no data | 18 % | 10 % | 6 to 10 % | 20 % | 20 % | 30 to 50 % | 20 % | 5 % | 8.3 % | no data | no data | 35 % | 30.8 % | 28.9 % | no data | > 3 % |
Why choose it, and why not
Good for
- Fuel cladding in water reactors: Zircaloy-4 is typically used in pressurized water and CANDU reactors (ATI).
- Low neutron absorption: 0.22 barns for Zircaloy-4, against 0.18 barns for zirconium (ATI).
- Corrosion in mild acid: under 0.13 mm/a for hot sulfuric acid and 0.05 mm/a for 70 % nitric acid at 120 °C (ATI).
Watch out for
- Hot hydrochloric acid attacks Zircaloy-4 at 0.36 mm/a, and hydrogen from water forms hydrides that embrittle the cladding.
- Hafnium contamination adds neutron absorption: 104 barns for hafnium against 0.22 barns for Zircaloy-4.
- Strength of Zircaloy strip depends on direction, so the grain orientation must be stated.
Zircaloy-4 and Zr-2.5Nb are the grades with the most published data for nuclear service, and the printed data support their use in water and steam. The research Zr-Al alloys are stronger at room temperature, but they have no commercial grade or corrosion data yet. Hydride cracking and hot hydrochloric acid are the main limits.
Technical details
For scientists and researchers. Everything above comes from the record below: every number with its method, its conditions and its source.
Other names and standards
The same grade under other systems, as datasheets and standards print them. Each code was checked against the page it comes from.
| System | Codes |
|---|---|
| UNS | R60802, R60804, R60904 |
| Trade name | Zircaloy-2, Zircaloy-4, ZIRLO |
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Density, Zircaloy-4 | Value printed in the ATI reactor-grade zirconium data sheet, Properties of Zircaloy-4 table | grade Zircaloy-4 (UNS R60804)temperature not statedunit in source 6.55 g/cc (0.237 lbs/cu.-in.) | — |
| 2 | Melting point, Zircaloy-4 | Value printed in the ATI reactor-grade zirconium data sheet | grade Zircaloy-4 (UNS R60804)unit in source 1850 °C (3,362 °F) | — |
| 3 | Thermal conductivity, Zircaloy-4 | Value printed in the ATI reactor-grade zirconium data sheet | grade Zircaloy-4 (UNS R60804)temperature not statedunit in source 21.5 Watts/m-K (149 BTU-in/hr-ft2-F) | — |
| 4 | Heat capacity, Zircaloy-4 | Value printed in the ATI reactor-grade zirconium data sheet; the table calls it heat capacity | grade Zircaloy-4 (UNS R60804)temperature not statedunit in source 0.285 J/g-°C (0.07 BTU/lb-°C) | — |
| 5 | Coefficient of thermal expansion, Zircaloy-4 at 25 degC | Value printed in the ATI reactor-grade zirconium data sheet | grade Zircaloy-4 (UNS R60804)temperature 25 °Cunit in source 6 µm/m °C (3.3 µin/in-°F) | — |
| 6 | Modulus of elasticity, Zircaloy-4 | Value printed in the ATI reactor-grade zirconium data sheet | grade Zircaloy-4 (UNS R60804)temperature not statedunit in source 99.3 Gpa (14,402 ksi) | — |
| 7 | Shear modulus, Zircaloy-4 | Value printed in the ATI reactor-grade zirconium data sheet | grade Zircaloy-4 (UNS R60804)temperature not statedunit in source 36.2 Gpa (5,249 ksi) | — |
| 8 | Poisson's ratio, Zircaloy-4 | Value printed in the ATI reactor-grade zirconium data sheet | grade Zircaloy-4 (UNS R60804)temperature not stated | — |
| 9 | Tensile strength, Zircaloy-4 longitudinal, room temperature | Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table | grade Zircaloy-4 (UNS R60804)temper annealed 2 mm thick striporientation longitudinaltemperature room temperatureunit in source 541 MPa (78.4 ksi) | — |
| 10 | Tensile strength, Zircaloy-4 transverse, room temperature | Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table | grade Zircaloy-4 (UNS R60804)temper annealed 2 mm thick striporientation transversetemperature room temperatureunit in source 515 MPa (74.6 ksi) | — |
| 11 | Tensile strength, Zircaloy-4 longitudinal, 288 degC | Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table | grade Zircaloy-4 (UNS R60804)temper annealed 2 mm thick striporientation longitudinaltemperature 288 °Cunit in source 271 MPa (39.3 ksi) | — |
| 12 | Tensile strength, Zircaloy-4 transverse, 288 degC | Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table | grade Zircaloy-4 (UNS R60804)temper annealed 2 mm thick striporientation transversetemperature 288 °Cunit in source 241 MPa (34.9 ksi) | — |
| 13 | Yield strength, Zircaloy-4 transverse, room temperature | Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table; the longitudinal yield in the same table (80 MPa) is not used, see gaps | grade Zircaloy-4 (UNS R60804)temper annealed 2 mm thick striporientation transversetemperature room temperatureunit in source 468 MPa (67.8 ksi) | — |
| 14 | Yield strength, Zircaloy-4 transverse, 288 degC | Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table | grade Zircaloy-4 (UNS R60804)temper annealed 2 mm thick striporientation transversetemperature 288 °Cunit in source 170 MPa (25.6 ksi) | — |
| 15 | Elongation, Zircaloy-4 longitudinal, room temperature | Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table | grade Zircaloy-4 (UNS R60804)temper annealed 2 mm thick striporientation longitudinaltemperature room temperature | — |
| 16 | Elongation, Zircaloy-4 transverse, room temperature | Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table | grade Zircaloy-4 (UNS R60804)temper annealed 2 mm thick striporientation transversetemperature room temperature | — |
| 17 | Thermal neutron cross section, Zircaloy-4 | Value printed in the ATI reactor-grade zirconium data sheet, thermal neutron cross sections table; the name is not in spores/property-canon.yaml, see gaps | grade Zircaloy-4 (UNS R60804)neutron thermalunit in source 0.22 barns | — |
| 18 | Thermal neutron cross section, zirconium | Value printed in the ATI reactor-grade zirconium data sheet, thermal neutron cross sections table | form zirconium elementneutron thermalunit in source 0.18 barns | — |
| 19 | Alpha to alpha plus beta transformation, Zircaloy-4 | Value printed in the ATI reactor-grade zirconium data sheet; non-canonical name, see gaps | grade Zircaloy-4 (UNS R60804)note beta phase starts to form on heating | — |
| 20 | Alpha plus beta to beta transformation, Zircaloy-4 | Value printed in the ATI reactor-grade zirconium data sheet; non-canonical name, see gaps | grade Zircaloy-4 (UNS R60804)note transformation to full beta phase | — |
| 21 | Offset yield strength, ZrAl14Ti3 (research alloy) | Value printed in the abstract of the open-access PMC paper; research alloy, not a commercial grade | alloy ZrAl14Ti3 (at. %), hot-rolled and quenchedtemperature room temperaturemeasure offset yield, as printed in the abstractscatter plus or minus 12 MPa | — |
| 22 | Tensile strength, ZrAl14Ti3 (research alloy) | Value printed in the abstract of the open-access PMC paper | alloy ZrAl14Ti3 (at. %), hot-rolled and quenchedtemperature room temperaturescatter plus or minus 19 MPa | — |
| 23 | Fracture elongation, ZrAl14Ti3 (research alloy) | Value printed in the abstract of the open-access PMC paper | alloy ZrAl14Ti3 (at. %), hot-rolled and quenchedtemperature room temperaturescatter plus or minus 1 % | — |
| 24 | Offset yield strength, ZrAl14Ti9 (research alloy) | Value printed in the abstract of the open-access PMC paper | alloy ZrAl14Ti9 (at. %), hot-rolled and quenchedtemperature room temperaturemeasure offset yieldscatter plus or minus 6 MPa | The paper says this is 110 MPa above ZrAl14Ti3 at the same condition. |
| 25 | Tensile strength, ZrAl14Ti9 (research alloy) | Value printed in the main text of the open-access PMC paper, comparison paragraph with ZrAl14Ti3 | alloy ZrAl14Ti9 (at. %), hot-rolled and quenchedtemperature room temperaturescatter plus or minus 7 MPa | — |
| 26 | Fracture elongation, ZrAl14Ti9 (research alloy) | Value printed in the abstract of the open-access PMC paper | alloy ZrAl14Ti9 (at. %), hot-rolled and quenchedtemperature room temperaturescatter plus or minus 2 % | — |
Corrosion and compatibility
What happens when it meets other materials and environments.
| Environment | Concern | What happens |
|---|---|---|
| Hydrochloric acid, 70 %, 160 °C (Zircaloy-4) | moderate | Hot concentrated hydrochloric acid attacks Zircaloy-4 at a measurable rate.1 |
| Ferric chloride, 1 %, 135 °C (Zircaloy-4) | moderate | A small amount of ferric chloride corrodes Zircaloy-4 at 0.18 mm/a.2 |
| Sulfuric acid, 70 %, 150 °C (Zircaloy-4) | low | Zircaloy-4 stays under 0.13 mm/a in hot sulfuric acid.3 |
| Nitric acid, 70 %, 120 °C (Zircaloy-4) | low | Zircaloy-4 barely corrodes in hot 70 % nitric acid.4 |
| Copper chloride, 0.1 %, 144 °C (Zircaloy-4) | low | Dilute copper chloride gives a low rate.5 |
| Sodium chloride, 25 %, 250 °C (Zircaloy-4) | none | Hot brine does not attack Zircaloy-4 measurably.6 |
| Nitric, sulfuric or hydrochloric acid with ferric, cupric or nitrate ions, above the boiling point | low | ATI says rates stay under 0.13 mm/a for these acid-and-impurity mixtures.7 |
| Air or water (oxide film) | not rated | Zircaloy-2 and Zircaloy-4 oxidise at the same rate in air or water, and their protection comes from the oxide film.8 |
| # | Environment | Details | Test conditions |
|---|---|---|---|
| 1 | Hydrochloric acid, 70 %, 160 °C (Zircaloy-4) | The corrosion table prints 0.36 mm/a (14 mpy) for Zircaloy-4 in 70 % HCl at 160 °C. | medium hydrochloric acid, 70 %temperature 160 °Cunit in source mm/a (MPY)rating basis Space Mushroom rating from the printed rate: none for nil, low below 0.1 mm/a, moderate from 0.1 mm/a |
| 2 | Ferric chloride, 1 %, 135 °C (Zircaloy-4) | The table prints 0.18 mm/a (7 mpy) for Zircaloy-4 in 1 % FeCl3 at 135 °C. | medium ferric chloride, 1 %temperature 135 °Cunit in source mm/a (MPY)rating basis as for the first entry |
| 3 | Sulfuric acid, 70 %, 150 °C (Zircaloy-4) | The table prints under 0.13 mm/a (under 5 mpy). | medium sulfuric acid, 70 %temperature 150 °Cunit in source mm/a (MPY) |
| 4 | Nitric acid, 70 %, 120 °C (Zircaloy-4) | The table prints 0.05 mm/a (2 mpy). | medium nitric acid, 70 %temperature 120 °Cunit in source mm/a (MPY) |
| 5 | Copper chloride, 0.1 %, 144 °C (Zircaloy-4) | The table prints 0.03 mm/a (1 mpy). | medium CuCl2, 0.1 %temperature 144 °Cunit in source mm/a (MPY) |
| 6 | Sodium chloride, 25 %, 250 °C (Zircaloy-4) | The table prints nil. | medium NaCl, 25 %temperature 250 °Cunit in source nil |
| 7 | Nitric, sulfuric or hydrochloric acid with ferric, cupric or nitrate ions, above the boiling point | The sheet says these solutions generally give corrosion rates of less than 0.13 mm/a (5 mpy) even at temperatures well above the boiling point. This is a general statement for the zirconium alloys, not a single printed test. | basis general statement in the zirconium alloy properties textunit in source mm/a (mpy) |
| 8 | Air or water (oxide film) | Wikipedia says oxidation occurs at the same rate in air or in water, that a sub-micrometre zirconium dioxide film forms quickly, and that Zircaloys 2 and 4 behave very similarly. No rate in mm or mg per area is printed in the page. | basis Wikipedia summary; no measured rate read in this run |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
No safety data sheet or hazard classification for these alloy grades was read in this run, so no personal hazard is stated here.
- Hydrogen
- Zirconium reacting with water releases hydrogen gas, according to the Wikipedia alloy summary. This is a reactor and storage concern.
If it fails
These are failure routes in the sources. The cladding route is documented in a paper, the acid routes are printed table results.
- Hydride cracking
- A Zircaloy-4 paper says hydride precipitation embrittles the alloy, and delayed hydride cracking threatens fuel cladding near notches and cracks. Wikipedia says hydrides blister and crack the cladding.
- Hot acid
- The corrosion table prints 0.36 mm/a for Zircaloy-4 in 70 % hydrochloric acid at 160 °C, and 0.18 mm/a in 1 % ferric chloride at 135 °C.
- Strip direction
- ATI says cold-rolled Zircaloy strip is much stronger in the transverse direction, so the orientation must be specified.
Handling and storage
- Grade
- Specify the grade, since tin, iron, chromium, nickel and niobium levels differ between Zircaloy-2, Zircaloy-4 and Zr-2.5Nb.
- Impurities
- Hydrogen is limited to 0.0025 % in Zircaloy-2 and Zircaloy-4, and to 0.0010 % in Zr-2.5Nb. Hafnium is limited to 0.010 %, because hafnium has a cross section of 104 barns.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Delayed hydride cracking of Zircaloy claddinghigh severity | Hydrogen uptake, and stress raisers such as notches and cracks, during reactor cycles or spent-fuel storage of high-burnup fuel rodsHydride precipitation embrittles Zircaloy, and delayed hydride cracking threatens the safety and structural integrity of fuel cladding. The paper gives no rate. |
| Hydrogen embrittlement of claddinghigh severity | Hydrogen released when zirconium oxidises in water diffuses into the alloy and forms hydridesHydrides are less dense and weaker than the alloy, and their formation results in blistering and cracking of the cladding. |
| Acid attack in hot hydrochloric acidmoderate severity | 70 % HCl at 160 °C, as in the Zircaloy-4 corrosion tableThe printed corrosion rate is 0.36 mm/a (14 mpy), so the alloy thins steadily in this service. |
| Directional strength of cold-rolled stripmoderate severity | Cold rolling produces a strong texture in Zircaloy strip, and the crystal basal poles sit about 35 degrees to the transverse planeATI says the anisotropy gives significantly higher yield strength in the transverse direction, so the strength of a strip depends on its orientation. Designers must state the direction. |
Side effects on surrounding parts
| Affects | Effect |
|---|---|
| Neutron economy in reactor cores | Reactor-grade zirconium limits hafnium to 0.010 % maximum. Hafnium has a thermal neutron cross section of 104 barns, against 0.18 barns for zirconium, so trace hafnium would absorb neutrons in the core. |
| Cladding structure through hydride formation | Zirconium reacting with water releases hydrogen gas, part of which diffuses into the alloy. |
Handling and storage
- Specify the grade, since Zircaloy-2, Zircaloy-4 and Zr-2.5Nb differ in tin, iron, nickel and niobium content (ATI composition table).
- Keep hydrogen impurity at or below 0.0025 % in Zircaloy-2 and Zircaloy-4, and at or below 0.0010 % in Zr-2.5Nb (ATI maximum impurities table).
- The impurity limits are printed as maxima: Zircaloy-2 and Zircaloy-4 carbon 0.027 %, nitrogen 0.0080 %, silicon 0.0120 %; Zr-2.5Nb carbon 0.027 %, nitrogen 0.0065 % (ATI maximum impurities table).
Mitigations
- Corrosion resistance is improved by deliberately growing a thicker, black, lustrous zirconium oxide layer (Wikipedia).
- Keep carbon below about 40 ppm and nitrogen below about 300 ppm, because larger amounts degrade corrosion resistance significantly (Wikipedia).
Supply and geography
How common the raw materials are and where they come from.
Zirconium mineral concentrates (zircon), 2025 mine production
- Top producers (2025)
- Australia 33.3%, South Africa 22.5%, Mozambique 13.3%, China 8.3%, United States 8.3%
- Recycling
- Companies in Oregon and Utah recycled zirconium from new scrap generated during metal production and fabrication, and from old scrap. The USGS does not quantify this recycling.
- Substitutes
- USGS: niobium, stainless steel and tantalum provide some substitution in nuclear applications.
Unwrought zirconium import sources, 2021 to 2024 window
- Top producers (2024)
- China 55%, Germany 15%, Canada 12%, France 7%
- Recycling
- Not quantified in the USGS summary.
Niobium (Zr-2.5Nb and ZIRLO alloying element), 2025 mine production
- Top producers (2025)
- Brazil 92.9%, Canada 5.4%, Congo (Kinshasa) 0.9%
- Recycling
- USGS: niobium recovery from scrap was negligible; the amount recycled was not available.
- Substitutes
- USGS: molybdenum, tantalum and titanium can be used as alloying elements in stainless and high-strength steels, and tantalum and tungsten in high-temperature superalloy applications; these substitutes carry a performance loss or higher cost.
Tin (Zircaloy alloying element), 2025 mine production
- Top producers (2025)
- China 24.5%, Indonesia 21%, Peru 11.4%, Brazil 9.7%
- Recycling
- USGS: about 17,000 tons of tin from old and new scrap was estimated recycled in 2025, 22 % of apparent consumption.
- Substitutes
- USGS: aluminum alloys, alternative copper-base alloys and plastics can substitute for tin in some uses.
Documents
Datasheets, safety data sheets, papers and standards you can open.
Full record
The complete spore, as stored. Free to reuse under CC-BY-4.0. Images keep the licence shown with each one.
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spore: profile
id: zirconium-alloys
spore_version: 0.2
family: refractory-metals
name: Zirconium alloys (Zircaloy, ZIRLO, Zr-2.5Nb, Zr-Al)
abbreviation: Zr alloys
role: corrosion-resistant structural alloys for nuclear fuel cladding, reactor pressure tubes and chemical-process equipment
category: metals
type: refractory-metals
summary: |
Zirconium alloys add small amounts of tin, iron, chromium, nickel or niobium to zirconium. The grades that matter most are Zircaloy-2 and Zircaloy-4 (fuel cladding in water reactors), Zr-2.5Nb (pressure tubes in CANDU reactors), and ZIRLO (Westinghouse cladding). In the ATI reactor-grade sheet, Zircaloy-4 has a density of 6.55 g/cc, a melting point of 1850 degC and a thermal conductivity of 21.5 W/m-K, and its annealed 2 mm strip has a room-temperature tensile strength of 541 MPa in the longitudinal direction. The corrosion table prints 0.36 mm/a for Zircaloy-4 in 70 % hydrochloric acid at 160 degC. A research alloy, ZrAl14Ti3, reaches 888 MPa offset yield strength at room temperature in one open-access paper, but no commercial Zr-Al grade was found.
best_for: Nuclear fuel cladding and reactor pressure tubes, where low thermal neutron absorption (0.22 barns for Zircaloy-4) and corrosion resistance in water and steam both matter (ATI reactor-grade sheet)
weakest_at: 'Hydride embrittlement: hydrogen from water oxidation forms hydrides that blister and crack the cladding (Wikipedia), and hot hydrochloric acid still attacks Zircaloy-4 at 0.36 mm/a'
identity:
formula: 'Zr-based alloys. Nominal Zircaloy-4 is Zr-1.5Sn-0.2Fe-0.1Cr (wt %). Zircaloy-2: Zr with Sn 1.20 to 1.70, Fe 0.07 to 0.20, Cr 0.05 to 0.15, Ni 0.03 to 0.08 wt %. Zircaloy-4: Zr with Sn 1.20 to 1.70, Fe 0.18 to 0.24, Cr 0.07 to 0.13 wt %. Zr-2.5Nb: Zr with Nb 2.40 to 2.80 wt %. ZIRLO: Zr with Nb about 1 and Sn 0.7 to 1 wt % (Wikipedia alloy table; iron level not given there). Zr-Al: research alloys ZrAl14Ti3 and ZrAl14Ti9 (at. %), not a commercial composition.'
source: ati-reactor-grade
where: Composition (weight percent) table, columns Zircaloy-2, Zircaloy-4 and Zr-2.5Nb; ZIRLO from the Wikipedia alloy table; Zr-Al from the PMC paper title and abstract
designations:
- system: UNS
code: R60802
source: ati-reactor-grade
where: Composition table, UNS Grade column, Zircaloy-2
- system: UNS
code: R60804
source: ati-reactor-grade
where: Composition table, UNS Grade column, Zircaloy-4
- system: UNS
code: R60904
source: ati-reactor-grade
where: Composition table, UNS Grade column, Zr-2.5Nb
- system: Trade name
code: Zircaloy-2
source: ati-reactor-grade
where: Zirconium alloys text, Zircaloy-2 paragraph
- system: Trade name
code: Zircaloy-4
source: ati-reactor-grade
where: Zirconium alloys text, Zircaloy-4 paragraph
- system: Trade name
code: ZIRLO
source: wikipedia-zr-alloys
where: Alloy table, ZIRLO row (Westinghouse; name stands for zirconium low oxidation)
tags:
environments: []
stresses:
- corrosion
applications:
- structures
- thermal-control
properties:
- benchmark: density
label: Density, Zircaloy-4
value: 6.55
unit: g/cc
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temperature: not stated
unit_in_source: 6.55 g/cc (0.237 lbs/cu.-in.)
method: Value printed in the ATI reactor-grade zirconium data sheet, Properties of Zircaloy-4 table
status: ground
source: ati-reactor-grade
where: Properties of Zircaloy-4 table, row Density
- benchmark: melting_point
label: Melting point, Zircaloy-4
value: 1850
unit: °C
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
unit_in_source: 1850 °C (3,362 °F)
method: Value printed in the ATI reactor-grade zirconium data sheet
status: ground
source: ati-reactor-grade
where: Properties of Zircaloy-4 table, row Melting Point
- benchmark: thermal_conductivity
label: Thermal conductivity, Zircaloy-4
value: 21.5
unit: W/m-K
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temperature: not stated
unit_in_source: 21.5 Watts/m-K (149 BTU-in/hr-ft2-F)
method: Value printed in the ATI reactor-grade zirconium data sheet
status: ground
source: ati-reactor-grade
where: Properties of Zircaloy-4 table, row Thermal Conductivity
- benchmark: specific_heat
label: Heat capacity, Zircaloy-4
value: 0.285
unit: J/g-°C
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temperature: not stated
unit_in_source: 0.285 J/g-°C (0.07 BTU/lb-°C)
method: Value printed in the ATI reactor-grade zirconium data sheet; the table calls it heat capacity
status: ground
source: ati-reactor-grade
where: Properties of Zircaloy-4 table, row Heat Capacity
- benchmark: cte
label: Coefficient of thermal expansion, Zircaloy-4 at 25 degC
value: 6
unit: µm/(m·°C)
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temperature: 25 °C
unit_in_source: 6 µm/m °C (3.3 µin/in-°F)
method: Value printed in the ATI reactor-grade zirconium data sheet
status: ground
source: ati-reactor-grade
where: Properties of Zircaloy-4 table, row Coefficient of Thermal Expansion at 25 C
- benchmark: elastic_modulus
label: Modulus of elasticity, Zircaloy-4
value: 99.3
unit: GPa
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temperature: not stated
unit_in_source: 99.3 Gpa (14,402 ksi)
method: Value printed in the ATI reactor-grade zirconium data sheet
status: ground
source: ati-reactor-grade
where: Properties of Zircaloy-4 table, row Modulus of Elasticity
- benchmark: shear_modulus
label: Shear modulus, Zircaloy-4
value: 36.2
unit: GPa
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temperature: not stated
unit_in_source: 36.2 Gpa (5,249 ksi)
method: Value printed in the ATI reactor-grade zirconium data sheet
status: ground
source: ati-reactor-grade
where: Properties of Zircaloy-4 table, row Shear Modulus
- benchmark: poissons_ratio
label: Poisson's ratio, Zircaloy-4
value: 0.37
unit: '-'
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temperature: not stated
method: Value printed in the ATI reactor-grade zirconium data sheet
status: ground
source: ati-reactor-grade
where: Properties of Zircaloy-4 table, row Poisson's Ratio
- benchmark: ultimate_tensile_strength
label: Tensile strength, Zircaloy-4 longitudinal, room temperature
value: 541
unit: MPa
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temper: annealed 2 mm thick strip
orientation: longitudinal
temperature: room temperature
unit_in_source: 541 MPa (78.4 ksi)
method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
status: ground
source: ati-reactor-grade
where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Ultimate Tensile Strength, Longitudinal, Room Temp
- benchmark: ultimate_tensile_strength
label: Tensile strength, Zircaloy-4 transverse, room temperature
value: 515
unit: MPa
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temper: annealed 2 mm thick strip
orientation: transverse
temperature: room temperature
unit_in_source: 515 MPa (74.6 ksi)
method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
status: ground
source: ati-reactor-grade
where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Ultimate Tensile Strength, Transverse, Room Temp
- benchmark: ultimate_tensile_strength
label: Tensile strength, Zircaloy-4 longitudinal, 288 degC
value: 271
unit: MPa
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temper: annealed 2 mm thick strip
orientation: longitudinal
temperature: 288 °C
unit_in_source: 271 MPa (39.3 ksi)
method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
status: ground
source: ati-reactor-grade
where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Ultimate Tensile Strength, Longitudinal, 288 C column
- benchmark: ultimate_tensile_strength
label: Tensile strength, Zircaloy-4 transverse, 288 degC
value: 241
unit: MPa
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temper: annealed 2 mm thick strip
orientation: transverse
temperature: 288 °C
unit_in_source: 241 MPa (34.9 ksi)
method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
status: ground
source: ati-reactor-grade
where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Ultimate Tensile Strength, Transverse, 288 C column
- benchmark: yield_strength
label: Yield strength, Zircaloy-4 transverse, room temperature
value: 468
unit: MPa
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temper: annealed 2 mm thick strip
orientation: transverse
temperature: room temperature
unit_in_source: 468 MPa (67.8 ksi)
method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table; the longitudinal yield in the same table (80 MPa) is not used, see gaps
status: ground
source: ati-reactor-grade
where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Yield Strength, Transverse, Room Temp
- benchmark: yield_strength
label: Yield strength, Zircaloy-4 transverse, 288 degC
value: 170
unit: MPa
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temper: annealed 2 mm thick strip
orientation: transverse
temperature: 288 °C
unit_in_source: 170 MPa (25.6 ksi)
method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
status: ground
source: ati-reactor-grade
where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Yield Strength, Transverse, 288 C column
- benchmark: elongation
label: Elongation, Zircaloy-4 longitudinal, room temperature
value: 28
unit: '%'
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temper: annealed 2 mm thick strip
orientation: longitudinal
temperature: room temperature
method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
status: ground
source: ati-reactor-grade
where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Elongation, Longitudinal, Room Temp
- benchmark: elongation
label: Elongation, Zircaloy-4 transverse, room temperature
value: 29
unit: '%'
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
temper: annealed 2 mm thick strip
orientation: transverse
temperature: room temperature
method: Value printed in the ATI reactor-grade zirconium data sheet, mechanical properties table
status: ground
source: ati-reactor-grade
where: Mechanical properties of Zircaloy-4 annealed 2 mm thick strip table, row Elongation, Transverse, Room Temp
- benchmark: thermal_neutron_cross_section
label: Thermal neutron cross section, Zircaloy-4
value: 0.22
unit: barns
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
neutron: thermal
unit_in_source: 0.22 barns
method: Value printed in the ATI reactor-grade zirconium data sheet, thermal neutron cross sections table; the name is not in spores/property-canon.yaml, see gaps
status: ground
source: ati-reactor-grade
where: Thermal neutron cross sections (barns) table, row Zircaloy-4
- benchmark: thermal_neutron_cross_section
label: Thermal neutron cross section, zirconium
value: 0.18
unit: barns
scope: material
conditions:
form: zirconium element
neutron: thermal
unit_in_source: 0.18 barns
method: Value printed in the ATI reactor-grade zirconium data sheet, thermal neutron cross sections table
status: ground
source: ati-reactor-grade
where: Thermal neutron cross sections (barns) table, row Zirconium
- benchmark: alpha_beta_transition_temperature
label: Alpha to alpha plus beta transformation, Zircaloy-4
value: 810
unit: °C
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
note: beta phase starts to form on heating
method: Value printed in the ATI reactor-grade zirconium data sheet; non-canonical name, see gaps
status: ground
source: ati-reactor-grade
where: Properties of Zircaloy-4 table, row Alpha to Alpha + Beta Phase Transformation; text on crystal structure
- benchmark: alpha_beta_transition_temperature
label: Alpha plus beta to beta transformation, Zircaloy-4
value: 980
unit: °C
scope: material
conditions:
grade: Zircaloy-4 (UNS R60804)
note: transformation to full beta phase
method: Value printed in the ATI reactor-grade zirconium data sheet; non-canonical name, see gaps
status: ground
source: ati-reactor-grade
where: Properties of Zircaloy-4 table, row Alpha + Beta to Beta Phase Transformation
- benchmark: yield_strength
label: Offset yield strength, ZrAl14Ti3 (research alloy)
value: 888
unit: MPa
scope: material
conditions:
alloy: ZrAl14Ti3 (at. %), hot-rolled and quenched
temperature: room temperature
measure: offset yield, as printed in the abstract
scatter: plus or minus 12 MPa
method: Value printed in the abstract of the open-access PMC paper; research alloy, not a commercial grade
status: ground
source: pmc-zral
where: Abstract, sentence beginning Mechanical property evaluation showed
- benchmark: ultimate_tensile_strength
label: Tensile strength, ZrAl14Ti3 (research alloy)
value: 1056
unit: MPa
scope: material
conditions:
alloy: ZrAl14Ti3 (at. %), hot-rolled and quenched
temperature: room temperature
scatter: plus or minus 19 MPa
method: Value printed in the abstract of the open-access PMC paper
status: ground
source: pmc-zral
where: Abstract, sentence beginning Mechanical property evaluation showed
- benchmark: elongation
label: Fracture elongation, ZrAl14Ti3 (research alloy)
value: 23
unit: '%'
scope: material
conditions:
alloy: ZrAl14Ti3 (at. %), hot-rolled and quenched
temperature: room temperature
scatter: plus or minus 1 %
method: Value printed in the abstract of the open-access PMC paper
status: ground
source: pmc-zral
where: Abstract, sentence beginning Mechanical property evaluation showed
- benchmark: yield_strength
label: Offset yield strength, ZrAl14Ti9 (research alloy)
value: 998
unit: MPa
scope: material
conditions:
alloy: ZrAl14Ti9 (at. %), hot-rolled and quenched
temperature: room temperature
measure: offset yield
scatter: plus or minus 6 MPa
method: Value printed in the abstract of the open-access PMC paper
status: ground
note: The paper says this is 110 MPa above ZrAl14Ti3 at the same condition.
source: pmc-zral
where: Abstract, sentence beginning The ZrAl14Ti9 alloy displayed
- benchmark: ultimate_tensile_strength
label: Tensile strength, ZrAl14Ti9 (research alloy)
value: 1069
unit: MPa
scope: material
conditions:
alloy: ZrAl14Ti9 (at. %), hot-rolled and quenched
temperature: room temperature
scatter: plus or minus 7 MPa
method: Value printed in the main text of the open-access PMC paper, comparison paragraph with ZrAl14Ti3
status: ground
source: pmc-zral
where: Main text, paragraph beginning Compared with ZrAl14Ti3 (results and discussion)
- benchmark: elongation
label: Fracture elongation, ZrAl14Ti9 (research alloy)
value: 23
unit: '%'
scope: material
conditions:
alloy: ZrAl14Ti9 (at. %), hot-rolled and quenched
temperature: room temperature
scatter: plus or minus 2 %
method: Value printed in the abstract of the open-access PMC paper
status: ground
source: pmc-zral
where: Abstract, sentence beginning The ZrAl14Ti9 alloy displayed
corrosion:
- environment: Hydrochloric acid, 70 %, 160 °C (Zircaloy-4)
headline: Hot concentrated hydrochloric acid attacks Zircaloy-4 at a measurable rate.
effect: The corrosion table prints 0.36 mm/a (14 mpy) for Zircaloy-4 in 70 % HCl at 160 °C.
rating: moderate
conditions:
medium: hydrochloric acid, 70 %
temperature: 160 °C
unit_in_source: mm/a (MPY)
rating_basis: 'Space Mushroom rating from the printed rate: none for nil, low below 0.1 mm/a, moderate from 0.1 mm/a'
source: ati-reactor-grade
where: Corrosion rate data for Zircaloy-4 table, row HCl 70 %, 160 °C
- environment: Ferric chloride, 1 %, 135 °C (Zircaloy-4)
headline: A small amount of ferric chloride corrodes Zircaloy-4 at 0.18 mm/a.
effect: The table prints 0.18 mm/a (7 mpy) for Zircaloy-4 in 1 % FeCl3 at 135 °C.
rating: moderate
conditions:
medium: ferric chloride, 1 %
temperature: 135 °C
unit_in_source: mm/a (MPY)
rating_basis: as for the first entry
source: ati-reactor-grade
where: Corrosion rate data for Zircaloy-4 table, row FeCl3 1 %, 135 °C
- environment: Sulfuric acid, 70 %, 150 °C (Zircaloy-4)
headline: Zircaloy-4 stays under 0.13 mm/a in hot sulfuric acid.
effect: The table prints under 0.13 mm/a (under 5 mpy).
rating: low
conditions:
medium: sulfuric acid, 70 %
temperature: 150 °C
unit_in_source: mm/a (MPY)
source: ati-reactor-grade
where: Corrosion rate data for Zircaloy-4 table, row H2SO4 70 %, 150 °C
- environment: Nitric acid, 70 %, 120 °C (Zircaloy-4)
headline: Zircaloy-4 barely corrodes in hot 70 % nitric acid.
effect: The table prints 0.05 mm/a (2 mpy).
rating: low
conditions:
medium: nitric acid, 70 %
temperature: 120 °C
unit_in_source: mm/a (MPY)
source: ati-reactor-grade
where: Corrosion rate data for Zircaloy-4 table, row HNO3 70 %, 120 °C
- environment: Copper chloride, 0.1 %, 144 °C (Zircaloy-4)
headline: Dilute copper chloride gives a low rate.
effect: The table prints 0.03 mm/a (1 mpy).
rating: low
conditions:
medium: CuCl2, 0.1 %
temperature: 144 °C
unit_in_source: mm/a (MPY)
source: ati-reactor-grade
where: Corrosion rate data for Zircaloy-4 table, row CuCl2 0.1 %, 144 °C
- environment: Sodium chloride, 25 %, 250 °C (Zircaloy-4)
headline: Hot brine does not attack Zircaloy-4 measurably.
effect: The table prints nil.
rating: none
conditions:
medium: NaCl, 25 %
temperature: 250 °C
unit_in_source: nil
source: ati-reactor-grade
where: Corrosion rate data for Zircaloy-4 table, row NaCl 25 %, 250 °C
- environment: Nitric, sulfuric or hydrochloric acid with ferric, cupric or nitrate ions, above the boiling point
headline: ATI says rates stay under 0.13 mm/a for these acid-and-impurity mixtures.
effect: The sheet says these solutions generally give corrosion rates of less than 0.13 mm/a (5 mpy) even at temperatures well above the boiling point. This is a general statement for the zirconium alloys, not a single printed test.
rating: low
conditions:
basis: general statement in the zirconium alloy properties text
unit_in_source: mm/a (mpy)
source: ati-reactor-grade
where: Zirconium alloy properties text, first paragraph under ZIRCONIUM ALLOY PROPERTIES
- environment: Air or water (oxide film)
headline: Zircaloy-2 and Zircaloy-4 oxidise at the same rate in air or water, and their protection comes from the oxide film.
effect: Wikipedia says oxidation occurs at the same rate in air or in water, that a sub-micrometre zirconium dioxide film forms quickly, and that Zircaloys 2 and 4 behave very similarly. No rate in mm or mg per area is printed in the page.
rating: unknown
conditions:
basis: Wikipedia summary; no measured rate read in this run
source: wikipedia-zr-alloys
where: Oxidation of zirconium alloy section
risks:
hazards: []
failure_risks:
- mode: Delayed hydride cracking of Zircaloy cladding
trigger: Hydrogen uptake, and stress raisers such as notches and cracks, during reactor cycles or spent-fuel storage of high-burnup fuel rods
consequence: Hydride precipitation embrittles Zircaloy, and delayed hydride cracking threatens the safety and structural integrity of fuel cladding. The paper gives no rate.
severity: high
source: arxiv-zircaloy4
where: Introduction, paragraph 1
- mode: Hydrogen embrittlement of cladding
trigger: Hydrogen released when zirconium oxidises in water diffuses into the alloy and forms hydrides
consequence: Hydrides are less dense and weaker than the alloy, and their formation results in blistering and cracking of the cladding.
severity: high
source: wikipedia-zr-alloys
where: Introduction, paragraph 1
- mode: Acid attack in hot hydrochloric acid
trigger: 70 % HCl at 160 °C, as in the Zircaloy-4 corrosion table
consequence: The printed corrosion rate is 0.36 mm/a (14 mpy), so the alloy thins steadily in this service.
severity: moderate
source: ati-reactor-grade
where: Corrosion rate data for Zircaloy-4 table, row HCl 70 %, 160 °C
- mode: Directional strength of cold-rolled strip
trigger: Cold rolling produces a strong texture in Zircaloy strip, and the crystal basal poles sit about 35 degrees to the transverse plane
consequence: ATI says the anisotropy gives significantly higher yield strength in the transverse direction, so the strength of a strip depends on its orientation. Designers must state the direction.
severity: moderate
source: ati-reactor-grade
where: Zirconium alloy text, crystal structure paragraph
side_effects:
- text: Reactor-grade zirconium limits hafnium to 0.010 % maximum. Hafnium has a thermal neutron cross section of 104 barns, against 0.18 barns for zirconium, so trace hafnium would absorb neutrons in the core.
affects: Neutron economy in reactor cores
source: ati-reactor-grade
where: Reactor grade paragraph; Thermal neutron cross sections table; Maximum impurities table
- text: Zirconium reacting with water releases hydrogen gas, part of which diffuses into the alloy.
affects: Cladding structure through hydride formation
source: wikipedia-zr-alloys
where: Introduction, paragraph 1
handling:
- text: Specify the grade, since Zircaloy-2, Zircaloy-4 and Zr-2.5Nb differ in tin, iron, nickel and niobium content (ATI composition table).
source: ati-reactor-grade
where: Composition (weight percent) table
- text: Keep hydrogen impurity at or below 0.0025 % in Zircaloy-2 and Zircaloy-4, and at or below 0.0010 % in Zr-2.5Nb (ATI maximum impurities table).
source: ati-reactor-grade
where: Maximum impurities table, row Hydrogen
- text: 'The impurity limits are printed as maxima: Zircaloy-2 and Zircaloy-4 carbon 0.027 %, nitrogen 0.0080 %, silicon 0.0120 %; Zr-2.5Nb carbon 0.027 %, nitrogen 0.0065 % (ATI maximum impurities table).'
source: ati-reactor-grade
where: Maximum impurities table, rows Carbon, Nitrogen, Silicon
mitigations:
- text: Corrosion resistance is improved by deliberately growing a thicker, black, lustrous zirconium oxide layer (Wikipedia).
source: wikipedia-zr-alloys
where: Oxidation of zirconium alloy section
- text: Keep carbon below about 40 ppm and nitrogen below about 300 ppm, because larger amounts degrade corrosion resistance significantly (Wikipedia).
source: wikipedia-zr-alloys
where: Oxidation of zirconium alloy section
uses:
- application: structures
device: Zircaloy-4 fuel cladding in pressurized water and CANDU reactors
example: ATI says Zircaloy-4 is typically used as fuel cladding in pressurized water reactors (PWR) and CANDU reactors, with the nominal composition Zr-1.5Sn-0.2Fe-0.1Cr.
source: ati-reactor-grade
where: Zirconium alloys text, Zircaloy-4 paragraph
- application: structures
device: Zircaloy-2 fuel cladding in boiling water reactors and calandria tubing in CANDU reactors
example: ATI says Zircaloy-2 has been predominantly used as fuel cladding in boiling water reactors (BWR) and as calandria tubing in CANDU reactors.
source: ati-reactor-grade
where: Zirconium alloys text, Zircaloy-2 paragraph
- application: structures
device: Zr-2.5Nb pressure tubes in CANDU reactors
example: ATI says Zr-2.5Nb has been used for pressure tubes in CANDU reactors, and that niobium increases its strength.
source: ati-reactor-grade
where: Zirconium alloys text, Zr-2.5Nb paragraph
- application: structures
device: ZIRLO fuel cladding in boiling and pressurized water reactors (Westinghouse)
example: The Wikipedia alloy table lists ZIRLO with Sn 0.7 to 1 and Nb 1 wt %, for cladding in BWR and PWR reactors, made by Westinghouse.
source: wikipedia-zr-alloys
where: Alloy table, ZIRLO row
supply:
- subject: Zirconium mineral concentrates (zircon), 2025 mine production
producers:
- country: Australia
share_percent: 33.3
year: 2025
- country: South Africa
share_percent: 22.5
year: 2025
- country: Mozambique
share_percent: 13.3
year: 2025
- country: China
share_percent: 8.3
year: 2025
- country: United States
share_percent: 8.3
year: 2025
critical_lists: []
recycling: Companies in Oregon and Utah recycled zirconium from new scrap generated during metal production and fabrication, and from old scrap. The USGS does not quantify this recycling.
substitutes:
- 'USGS: niobium, stainless steel and tantalum provide some substitution in nuclear applications.'
source: usgs-mcs2026-zirconium
where: 'World Mine Production and Reserves table, zirconium mineral concentrates, 2025 column: Australia 400, South Africa 270, Mozambique 160, China 100, United States 100, world total 1,200 thousand t (rounded). Shares calculated by Space Mushroom as country value divided by the printed world total. Recycling and Substitutes sections.'
- subject: Unwrought zirconium import sources, 2021 to 2024 window
producers:
- country: China
share_percent: 55
year: 2024
- country: Germany
share_percent: 15
year: 2024
- country: Canada
share_percent: 12
year: 2024
- country: France
share_percent: 7
year: 2024
critical_lists: []
recycling: Not quantified in the USGS summary.
substitutes: []
source: usgs-mcs2026-zirconium
where: 'Import Sources (2021-24), Zirconium unwrought: China 55 %, Germany 15 %, Canada 12 %, France 7 %. The year given is the end of the window.'
- subject: Niobium (Zr-2.5Nb and ZIRLO alloying element), 2025 mine production
producers:
- country: Brazil
share_percent: 92.9
year: 2025
- country: Canada
share_percent: 5.4
year: 2025
- country: Congo (Kinshasa)
share_percent: 0.9
year: 2025
critical_lists: []
recycling: 'USGS: niobium recovery from scrap was negligible; the amount recycled was not available.'
substitutes:
- 'USGS: molybdenum, tantalum and titanium can be used as alloying elements in stainless and high-strength steels, and tantalum and tungsten in high-temperature superalloy applications; these substitutes carry a performance loss or higher cost.'
source: usgs-mcs2026-niobium
where: 'World Mine Production and Reserves table, mine production 2025e: Brazil 104,000, Canada 6,000, Congo (Kinshasa) 970 thousand t; world total 112,000 (rounded). Shares calculated by Space Mushroom. Recycling and Substitutes sections.'
- subject: Tin (Zircaloy alloying element), 2025 mine production
producers:
- country: China
share_percent: 24.5
year: 2025
- country: Indonesia
share_percent: 21
year: 2025
- country: Peru
share_percent: 11.4
year: 2025
- country: Brazil
share_percent: 9.7
year: 2025
critical_lists: []
recycling: 'USGS: about 17,000 tons of tin from old and new scrap was estimated recycled in 2025, 22 % of apparent consumption.'
substitutes:
- 'USGS: aluminum alloys, alternative copper-base alloys and plastics can substitute for tin in some uses.'
source: usgs-mcs2026-tin
where: 'World Mine Production and Reserves table, mine production 2025e: China 71,000, Indonesia 61,000, Peru 33,000, Brazil 28,000 thousand t; world total 290,000 (rounded). Shares calculated by Space Mushroom. Recycling and Substitutes sections.'
documents:
- title: 'ATI Zirconium Alloys technical data sheet: Reactor Grade Zirconium (Zircaloy-2, Zircaloy-4, Zr-2.5Nb), version 1, 2015'
type: datasheet
url: https://www.atimaterials.com/Products/Documents/datasheets/zirconium/alloy/Zr_nuke_waste_disposal_v1.pdf
year: 2015
- title: Liu et al., Characterisation of microstructural creep, strain rate and temperature sensitivity and computational crystal plasticity in Zircaloy-4, arXiv:2109.05333
type: paper
url: https://arxiv.org/pdf/2109.05333
year: 2021
- title: Zirconium alloys, Wikipedia (alloy composition table, oxidation, hydrides, applications; article titled Zircaloy)
type: database
url: https://en.wikipedia.org/wiki/Zircaloy
year: 2026
- title: Zirconium, Wikipedia (Kroll process, standard atomic weight)
type: database
url: https://en.wikipedia.org/wiki/Zirconium
year: 2026
- title: 'USGS Mineral Commodity Summaries 2026: Zirconium and Hafnium'
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zirconium-hafnium.pdf
year: 2026
- title: 'USGS Mineral Commodity Summaries 2026: Niobium (Columbium)'
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf
year: 2026
- title: 'USGS Mineral Commodity Summaries 2026: Tin'
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tin.pdf
year: 2026
- title: 'Open-access paper: Microstructure and Mechanical Properties of Hot-Rolled ZrAl14Ti3 and ZrAl14Ti9 Alloys (PMC12525182)'
type: paper
url: https://pmc.ncbi.nlm.nih.gov/articles/PMC12525182/
gaps:
- No property values for Zircaloy-2, ZIRLO or Zr-2.5Nb were read in a page fetched in this run. The ATI sheet prints tensile and thermal values for Zircaloy-4 only. Open Zr-2.5Nb tensile papers (OSTI record, Springer article) returned no readable text here; search snippets are not used.
- ZIRLO iron content is not printed in any page read in this run. The Wikipedia alloy table gives only Sn and Nb for ZIRLO, so the nominal iron level is left out.
- Zircaloy-4 longitudinal yield strength at room temperature (80 MPa) in the ATI table sits oddly next to its 541 MPa tensile strength and looks anomalous, so it is not recorded. Only transverse and 288 degC yields are used.
- Zr-Al values come from two research alloys (ZrAl14Ti3 and ZrAl14Ti9, at. %, hot-rolled and quenched) in one paper. No commercial Zr-Al grade, and no property range across the Zr-Al composition, was found. Patent and supplier snippets were not used.
- Zr-Al and the commercial alloys have no hazard, SDS or GHS record read in this run, so risks.hazards is empty. The zirconium metal powder hazard is covered in the zirconium.yaml profile, not here.
- 'Non-canonical property names used: thermal_neutron_cross_section and alpha_beta_transition_temperature. Neither is in spores/property-canon.yaml.'
- Hardness (89 Rb for Zircaloy-4), electrical resistivity, outgassing and radiation damage were printed or searched but not recorded as values for these alloys.
- Critical-mineral status of zirconium, tin and niobium is not stated in the USGS summaries read here, so critical_lists is empty.
- EN, DIN and JIS designations for these grades were not found in a page read in this run. Only UNS, ASTM-style trade names and the ZIRLO trade name are listed.
- No media is included for this profile.
- The year of the PMC paper is not printed on the page read in this run, so the source record gives no year.
sources:
ati-reactor-grade:
title: 'Zirconium Alloys: Reactor Grade Zirconium, ATI Technical Data Sheet, version 1'
id: UNS R60802 (Zircaloy-2), R60804 (Zircaloy-4), R60904 (Zr-2.5Nb)
url: https://www.atimaterials.com/Products/Documents/datasheets/zirconium/alloy/Zr_nuke_waste_disposal_v1.pdf
year: 2015
kind: datasheet
license: Manufacturer datasheet, typical data, not for specification (cited, not reproduced)
arxiv-zircaloy4:
title: Characterisation of microstructural creep, strain rate and temperature sensitivity and computational crystal plasticity in Zircaloy-4 (Liu et al.)
id: arXiv:2109.05333
url: https://arxiv.org/pdf/2109.05333
year: 2021
kind: paper
license: arXiv preprint (cited, not reproduced)
wikipedia-zr-alloys:
title: Zirconium alloys (Wikipedia, article reached from the Zircaloy redirect)
url: https://en.wikipedia.org/wiki/Zircaloy
year: 2026
kind: web
license: CC BY-SA 4.0 (cited, not reproduced)
wikipedia-zirconium:
title: Zirconium (Wikipedia; element, Kroll process, standard atomic weight)
url: https://en.wikipedia.org/wiki/Zirconium
year: 2026
kind: web
license: CC BY-SA 4.0 (cited, not reproduced)
usgs-mcs2026-zirconium:
title: 'Mineral Commodity Summaries 2026: Zirconium and Hafnium (Shelby N. Johnston, U.S. Geological Survey)'
id: USGS MCS 2026, February 2026
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-zirconium-hafnium.pdf
year: 2026
kind: report
license: public domain (USGS)
usgs-mcs2026-niobium:
title: 'Mineral Commodity Summaries 2026: Niobium (Columbium)'
id: USGS MCS 2026, February 2026
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-niobium.pdf
year: 2026
kind: report
license: public domain (USGS)
usgs-mcs2026-tin:
title: 'Mineral Commodity Summaries 2026: Tin'
id: USGS MCS 2026, February 2026
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tin.pdf
year: 2026
kind: report
license: public domain (USGS)
pmc-zral:
title: Microstructure and Mechanical Properties of Hot-Rolled ZrAl14Ti3 and ZrAl14Ti9 Alloys (open access, PMC12525182)
id: PMID 41095285, PMCID PMC12525182
url: https://pmc.ncbi.nlm.nih.gov/articles/PMC12525182/
kind: paper
license: CC BY 4.0
license: CC-BY-4.0
updated: '2026-10-26'
review:
status: draft
method: assistant
checked_values: 26
unreachable: 2
caveats: 3
note: 'Read by an AI assistant on 2026-10-26 from the ATI reactor-grade PDF, the arXiv PDF, the PMC paper, the Wikipedia alloy and zirconium pages, and the USGS niobium, tin and zirconium summaries. Unreachable in this run: the OSTI ZIRLO record and the Springer Zr-2.5Nb article (timeout and blocked page). Caveats: the Zircaloy-4 longitudinal yield (80 MPa) is not used; ZIRLO and Zr-2.5Nb carry no numeric properties; Zr-Al values are from research alloys.'
story:
recipe:
line: Zircaloys are zirconium with small additions of tin, iron, chromium and, for Zircaloy-2, nickel. Zircaloy-4 has the nominal composition Zr-1.5Sn-0.2Fe-0.1Cr (ATI; also arXiv). Zr-2.5Nb is zirconium with 2.4 to 2.8 wt % niobium. Most zirconium metal is made by reducing zirconium(IV) chloride with magnesium in the Kroll process (Wikipedia), and the alloy is then melted with its additions.
parts:
- name: Zirconium
symbol: Zr
share_percent: 95
role: Base metal. Wikipedia says nuclear-grade zirconium alloys are more than 95 weight percent zirconium.
- name: Tin
symbol: Sn
share_percent: 1.2
share_high: 1.7
role: Main alloying element in Zircaloy-2, Zircaloy-4 and ZIRLO; adds strength and helps corrosion resistance (ATI composition table).
- name: Iron
symbol: Fe
share_percent: 0.18
share_high: 0.24
role: Zircaloy-4 addition; Zircaloy-2 has 0.07 to 0.20 wt % (ATI composition table).
- name: Chromium
symbol: Cr
share_percent: 0.07
share_high: 0.13
role: Zircaloy-4 addition; Zircaloy-2 has 0.05 to 0.15 wt % (ATI composition table).
- name: Niobium
symbol: Nb
share_percent: 2.4
share_high: 2.8
role: Zr-2.5Nb binary alloy addition for strength (ATI composition table). ZIRLO has about 1 wt % Nb (Wikipedia).
risk_groups:
- title: For people
level: 0
verdict: No hazard class found
lead: No safety data sheet or hazard classification for these alloy grades was read in this run, so no personal hazard is stated here.
points:
- label: Hydrogen
line: Zirconium reacting with water releases hydrogen gas, according to the Wikipedia alloy summary. This is a reactor and storage concern.
- title: If it fails
lead: These are failure routes in the sources. The cladding route is documented in a paper, the acid routes are printed table results.
points:
- label: Hydride cracking
line: A Zircaloy-4 paper says hydride precipitation embrittles the alloy, and delayed hydride cracking threatens fuel cladding near notches and cracks. Wikipedia says hydrides blister and crack the cladding.
- label: Hot acid
line: The corrosion table prints 0.36 mm/a for Zircaloy-4 in 70 % hydrochloric acid at 160 °C, and 0.18 mm/a in 1 % ferric chloride at 135 °C.
- label: Strip direction
line: ATI says cold-rolled Zircaloy strip is much stronger in the transverse direction, so the orientation must be specified.
- title: Handling and storage
points:
- label: Grade
line: Specify the grade, since tin, iron, chromium, nickel and niobium levels differ between Zircaloy-2, Zircaloy-4 and Zr-2.5Nb.
- label: Impurities
line: Hydrogen is limited to 0.0025 % in Zircaloy-2 and Zircaloy-4, and to 0.0010 % in Zr-2.5Nb. Hafnium is limited to 0.010 %, because hafnium has a cross section of 104 barns.
why: Zircaloy-2 and Zircaloy-4 are the workhorse fuel cladding alloys of water reactors. Zircaloy-4 has the same tin content as Zircaloy-2 but more iron and no nickel, which the ATI sheet says reduces hydrogen uptake in certain reactor conditions. Zr-2.5Nb adds niobium for strength and is used for CANDU pressure tubes. ZIRLO, a Westinghouse alloy with about 1 wt % niobium and 0.7 to 1 wt % tin, is used for cladding in boiling and pressurized water reactors. The alloys keep the low thermal neutron cross section of zirconium (0.18 barns) and its corrosion resistance, with Zircaloy-4 at 0.22 barns.
uses:
- where: Fuel cladding in pressurized water reactors
line: ATI says Zircaloy-4 is typically used as fuel cladding in pressurized water reactors and CANDU reactors. Wikipedia lists Zircaloy-4 as cladding and structural components in BWR, PWR and CANDU reactors.
- where: Cladding and calandria tubing in boiling water and CANDU reactors
line: ATI says Zircaloy-2 has been used mainly as fuel cladding in boiling water reactors and as calandria tubing in CANDU reactors.
- where: Pressure tubes in CANDU reactors
line: ATI says Zr-2.5Nb has been used for CANDU pressure tubes. Wikipedia adds that a Zr-2.5Nb alloy is formed into a knee or hip implant and then oxidised to give a hard ceramic bearing surface.
- where: ZIRLO cladding (Westinghouse)
line: The Wikipedia alloy table lists ZIRLO as Westinghouse cladding for BWR and PWR reactors, with 0.7 to 1 wt % Sn and 1 wt % Nb.
can_do:
- label: Resist hot acid
value: 0.05 mm/a
line: Zircaloy-4 corrodes at 0.05 mm/a in 70 % nitric acid at 120 °C, and under 0.13 mm/a in 70 % sulfuric acid at 150 °C. Hydrochloric acid at 70 % and 160 °C is worse, at 0.36 mm/a.
- label: Carry heat
value: 21.5 W/m-K
benchmark: thermal_conductivity
line: Zircaloy-4 conducts heat at 21.5 W/m-K. ATI says zirconium alloys conduct heat better than stainless steel alloys.
- label: Weight
value: 6.55 g/cc
benchmark: density
line: Zircaloy-4 has a density of 6.55 g/cc, and the ATI sheet gives its melting point as 1850 °C.
- label: Tensile strength
value: 541 MPa
benchmark: ultimate_tensile_strength
line: Annealed Zircaloy-4 strip has a room-temperature tensile strength of 541 MPa longitudinally and 515 MPa transversely. At 288 °C the longitudinal value falls to 271 MPa.
- label: Research alloy strength
value: 888 MPa
benchmark: yield_strength
line: In one open-access paper, the research alloy ZrAl14Ti3 reached an offset yield strength of 888 MPa, and ZrAl14Ti9 reached 998 MPa, with about 23 % fracture elongation for both. These are research alloys with no commercial grade.
compare: 'Zircaloy-4 has a thermal neutron cross section of 0.22 barns, against 0.18 barns for pure zirconium, and a thermal conductivity of 21.5 W/m-K. Zr-Al is a different class: the research alloys reach about 888 to 1069 MPa at room temperature, far above the 541 MPa annealed Zircaloy-4 strip, but no corrosion or thermal data were found for them. Read the rows as grades of one family, not as a ranking that covers every alloy.'
compare_rows:
- label: Density
benchmark: density
- label: Thermal conductivity
benchmark: thermal_conductivity
- label: Tensile strength
benchmark: ultimate_tensile_strength
handling:
- Specify the grade (Zircaloy-2, Zircaloy-4, Zr-2.5Nb or ZIRLO), because tin, iron, nickel and niobium levels differ.
- 'Keep hydrogen impurity low: 0.0025 % maximum in Zircaloy-2 and -4, 0.0010 % in Zr-2.5Nb.'
- Keep carbon and nitrogen low, since large amounts degrade corrosion resistance (Wikipedia).
good_for:
- 'Fuel cladding in water reactors: Zircaloy-4 is typically used in pressurized water and CANDU reactors (ATI).'
- 'Low neutron absorption: 0.22 barns for Zircaloy-4, against 0.18 barns for zirconium (ATI).'
- 'Corrosion in mild acid: under 0.13 mm/a for hot sulfuric acid and 0.05 mm/a for 70 % nitric acid at 120 °C (ATI).'
watch_out:
- Hot hydrochloric acid attacks Zircaloy-4 at 0.36 mm/a, and hydrogen from water forms hydrides that embrittle the cladding.
- 'Hafnium contamination adds neutron absorption: 104 barns for hafnium against 0.22 barns for Zircaloy-4.'
- Strength of Zircaloy strip depends on direction, so the grain orientation must be stated.
verdict: Zircaloy-4 and Zr-2.5Nb are the grades with the most published data for nuclear service, and the printed data support their use in water and steam. The research Zr-Al alloys are stronger at room temperature, but they have no commercial grade or corrosion data yet. Hydride cracking and hot hydrochloric acid are the main limits.
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.
| # | Source | Type | Year | Used for |
|---|---|---|---|---|
| Zirconium Alloys: Reactor Grade Zirconium, ATI Technical Data Sheet, version 1 | datasheet | 2015 | 37 values | |
| Characterisation of microstructural creep, strain rate and temperature sensitivity and computational crystal plasticity in Zircaloy-4 (Liu et al.) | paper | 2021 | 1 value | |
| Zirconium alloys (Wikipedia, article reached from the Zircaloy redirect) | web | 2026 | 6 values | |
| Zirconium (Wikipedia; element, Kroll process, standard atomic weight) | web | 2026 | 0 values | |
| Mineral Commodity Summaries 2026: Zirconium and Hafnium (Shelby N. Johnston, U.S. Geological Survey) | report | 2026 | 2 values | |
| Mineral Commodity Summaries 2026: Niobium (Columbium) | report | 2026 | 1 value | |
| Mineral Commodity Summaries 2026: Tin | report | 2026 | 1 value | |
| Microstructure and Mechanical Properties of Hot-Rolled ZrAl14Ti3 and ZrAl14Ti9 Alloys (open access, PMC12525182) | paper | 6 values |