Aluminium-boron carbide composite (Metamic, BORAL) Al-B4C
Al + B4C (aluminium matrix with boron carbide particles
Also known as Metamic
Aluminium-boron carbide composite is an aluminium matrix loaded with boron carbide (B4C) particles, which absorb neutrons.
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.
Neutron absorption
75.5 % shielded
Yield strength
157 MPa
Hardness
113 HV
Temperature limit
400 °C
Recipe, share of the weight
- Al balance (the rest of the mass)Aluminium
- B4C 15 to 50%Boron carbide
Best for
Neutron absorber panels in spent-fuel pool racks and transport-cask baskets, where boron content matters (NRC 2020; Holtec)
Weakest at
Ductility at high B4C loading: elongation falls from 10.6 % at 15 wt% B4C to 1.0 % at 40 wt% (NRC Table 2); no flight data
Risk at a glance
- People Low. Dust hazard when machining
- If it fails Moderate. Loss of ductility at high B4C loading
- Corrosion Moderate. Mill-finished Metamic lost 3 percent of its weight in BWR water over 9,020 hours, with pitting; anodized Metamic lost none.
Quick facts: Al-B4C
| Property | Value | Basis |
|---|---|---|
| Density | 2.5 to 2.65 g/cm³ | 1 sourced value |
| Yield strength | 110 to 227 MPa | 4 sourced values across conditions |
| Tensile strength | 68.9 to 277 MPa | 5 sourced values across conditions |
| Young's modulus | 62.1 GPa | 1 sourced value |
| Thermal conductivity | 156 W/(m·K) | 1 sourced value |
| Maximum service temperature | 400 °C | 1 sourced value |
What is the density of Aluminium-boron carbide composite (Al-B4C)?
Aluminium-boron carbide composite (Al-B4C) has a density of 2.5 to 2.65 g/cm³. The source and test conditions are listed in the properties table on this page.
What is the thermal conductivity of Aluminium-boron carbide composite (Al-B4C)?
Aluminium-boron carbide composite (Al-B4C) has a thermal conductivity of 156 W/(m·K). The source and test conditions are listed in the properties table on this page.
What is the yield strength of Aluminium-boron carbide composite (Al-B4C)?
Aluminium-boron carbide composite (Al-B4C) has a yield strength of 110 to 227 MPa. The range covers 4 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the tensile strength of Aluminium-boron carbide composite (Al-B4C)?
Aluminium-boron carbide composite (Al-B4C) has a tensile strength of 68.9 to 277 MPa. The range covers 5 sourced values across the tempers, forms and test conditions the sources report; room-temperature values are used where a source states a temperature.
What is the Young's modulus of Aluminium-boron carbide composite (Al-B4C)?
Aluminium-boron carbide composite (Al-B4C) has a Young's modulus of 62.1 GPa. The source and test conditions are listed in the properties table on this page.
What is Aluminium-boron carbide composite (Al-B4C) used for?
Uses recorded in the sources include Neutron absorber panels in spent-fuel pool storage racks (BORAL, Metamic and Boralcan); Fuel basket of the HI-STAR 180 transport cask (uses Metamic-HT, a Holtec variant); Al6061 plate with 50 vol% B4C for neutron shielding (ground test, not flown).
Why it exists
Aluminium-boron carbide composite puts boron carbide particles into an aluminium matrix, so a structural-looking panel can also absorb neutrons. Metamic and BORAL are the two products the NRC reviewed for spent-fuel storage. NASA Langley tested an aluminium 6061 version with boron carbide for space radiation shielding in a ground study. The composite is chosen when neutron absorption has to be built into the material, not added as a separate shield.
Where it's used
Spent fuel pool racks
The NRC reports that BORAL is used in about 60 percent of US spent fuel pools, and Metamic and Boralcan together in about 20 percent.
Transport cask fuel basket
Holtec cites docket 71-9325 for the HI-STAR 180 transport cask, whose fuel basket uses Metamic-HT, a Holtec variant.
Ground test for space radiation
NASA Langley tested Al6061 with 50 vol% B4C in a ground neutron test, and its model suggests it also helps against galactic cosmic rays. It is not a flight result.
Recipe
Al + B4C (aluminium matrix with boron carbide particles; Metamic uses an aluminium 6061 matrix)
Aluminium-boron carbide composite is an aluminium matrix that holds boron carbide (B4C) particles. Wikipedia notes that boron carbide absorbs neutrons without forming long-lived radionuclides, which is why it is used in nuclear shielding. Metamic is made by powder metallurgy from high-purity aluminium powder and nuclear grade boron carbide (ASTM C750 Type 1), per Holtec, then extruded into preforms and hot rolled to final thickness (NRC). BORAL is a different form: a cermet core of B4C and aluminium powder in 1100 aluminium cladding, hot rolled into plate or sheet (NRC).
| Ingredient | Share of the weight | What it does |
|---|---|---|
| Aluminium Al | balance (the rest of the mass) | The matrix. Metamic uses aluminium 6061; the BORAL core uses 1100 aluminium powder and cladding. It holds the particles and carries the load. |
| Boron carbide B4C | 15 to 50% | The neutron absorber. Boron captures neutrons, so the B4C content sets how much neutron absorption the panel gives. |
Weight shares are as printed in the sources.
What it can do
Neutron absorption
75.5 % shielded
measured
At 50 vol% B4C in Al6061, NASA measured 75.5 % shielded in an indium-foil neutron test. NASA reports a shielding effectiveness more than 110 times that of pristine Al6061.
Yield strength
157 MPa
measured
Metamic averages a yield strength of 157 MPa at 15 wt% B4C and 227 MPa at 31 wt% B4C, according to NRC Table 2.
Hardness
113 HV
measured
NASA measured 157.6 Hv for Al6061 with 20 vol% B4C, against 113.0 Hv for pristine Al6061.
Temperature limit
400 °C
measured
The supplier gives a long-term operating limit of 400 °C for its board.
How it compares
Compared with pristine Al6061, B4C raises hardness and lowers thermal conductivity. NASA reports Vickers hardness of 157.6 Hv at 20 vol% B4C against 113.0 Hv for pristine Al6061, and about 156 W/mK for pristine Al6061 at room temperature, with the composite values shown only in a figure. Within the Metamic loadings, more B4C means less stretch: elongation is 10.6 % at 15 wt% and 1.0 % at 40 wt%, while yield strength is 157 MPa at 15 wt% and 207 MPa at 40 wt%.
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.
| Measurement | Al-B4C |
|---|---|
| Thermal behavior and safety | |
| Thermal conductivity, pristine Al6061 at room temperature | 156 W/mK16 |
| Physical and electrical | |
| Density, Al + B4C board (supplier range)Range printed in a supplier product table | 2.5 to 2.65 g/cm³1 |
| Vickers hardness, pristine Al6061 control (113.0 +/- 7.2 Hv as printed) | 113 HV14 |
| Vickers hardness, Al6061 with 20 vol% B4C | 157.6 HV15 |
| Compaction density, BORAL cermet core (survey of 40 panels) | 89.5 to 96.1 % of theoretical22 |
| Other measurements | |
| Yield strength, Metamic 15 wt% B4C | 157 MPa2 |
| Yield strength, Metamic 31 wt% B4C | 227 MPa3 |
| Yield strength, Metamic 40 wt% B4C | 207 MPa4 |
| Ultimate tensile strength, Metamic 15 wt% B4C | 232 MPa5 |
| Ultimate tensile strength, Metamic 31 wt% B4C | 272 MPa6 |
| Ultimate tensile strength, Metamic 40 wt% B4C | 277 MPa7 |
| Elongation to failure, Metamic 15 wt% B4C | 10.6 %8 |
| Elongation to failure, Metamic 31 wt% B4C | 2.4 %9 |
| Elongation to failure, Metamic 40 wt% B4C | 1 %10 |
| Yield strength, Al + B4C board (supplier minimum) | > 110 MPa11 |
| Tensile strength, Al + B4C board (supplier minimum) | > 200 MPa12 |
| Elongation after fracture, Al + B4C board (supplier minimum) | > 1.8 %13 |
| Neutron shielding, Al6061 with 50 vol% B4C (indium foil, percent shielded) | 75.5 % shielded17 |
| Long-term operating temperature, Al + B4C board (supplier limit) | < 400 °C18 |
| Modulus of elasticity, BORAL cermet with 1100 aluminium cladding | 9 msi19 |
| Tensile strength, BORAL cermet with 1100 aluminium cladding | 10 ksi20 |
| Elongation, BORAL cermet with 1100 aluminium cladding | 0.1 %21 |
Why choose it, and why not
Good for
- Neutron absorption in spent fuel racks. NRC reports BORAL in about 60 percent of US spent fuel pools.
- Neutron absorption with some strength. Metamic at 15 wt% B4C has a yield strength of 157 MPa and 10.6 % elongation.
Watch out for
- Ductility falls with B4C content: 2.4 % elongation at 31 wt% and 1.0 % at 40 wt%.
- Pitting in BWR water and in galvanic contact with 304L stainless steel. Anodizing helps.
- No flight data. The NASA result is a ground neutron test and a model.
The composite is an established neutron absorber in nuclear storage, backed by the NRC's 2020 review of qualification tests. Its space role rests on one NASA ground study. Density is a supplier range, and the Metamic tensile values are averages, so confirm the grade and loading before using any number.
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 |
|---|---|
| Trade name | Metamic |
Notes
The method, full conditions and any caveat for the numbered rows above.
| # | Measurement | Method | Conditions | Caveat |
|---|---|---|---|---|
| 1 | Density, Al + B4C board (supplier range) | — | composition Al + B4C, B4C mass fraction 15% to 50% as printedbasis at least 95% of theoretical density, as printedform board, hot rolled or hot isostatic pressed (product page) | The same page's description section prints about 2.5-2.7 g/cm3 for this material; the two ranges are kept as printed. |
| 2 | Yield strength, Metamic 15 wt% B4C | Average mechanical properties as printed in the NRC review, citing the EPRI handbook | matrix aluminium 6061B4C wt percent 15basis average, as printed; test temperature and specimen form not stated in Table 2 | — |
| 3 | Yield strength, Metamic 31 wt% B4C | Average mechanical properties as printed in the NRC review, citing the EPRI handbook | matrix aluminium 6061B4C wt percent 31basis average, as printed; test temperature and specimen form not stated in Table 2 | — |
| 4 | Yield strength, Metamic 40 wt% B4C | Average mechanical properties as printed in the NRC review, citing the EPRI handbook | matrix aluminium 6061B4C wt percent 40basis average, as printed; test temperature and specimen form not stated in Table 2 | — |
| 5 | Ultimate tensile strength, Metamic 15 wt% B4C | Average mechanical properties as printed in the NRC review, citing the EPRI handbook | matrix aluminium 6061B4C wt percent 15basis average, as printed; test temperature and specimen form not stated in Table 2 | — |
| 6 | Ultimate tensile strength, Metamic 31 wt% B4C | Average mechanical properties as printed in the NRC review, citing the EPRI handbook | matrix aluminium 6061B4C wt percent 31basis average, as printed; test temperature and specimen form not stated in Table 2 | — |
| 7 | Ultimate tensile strength, Metamic 40 wt% B4C | Average mechanical properties as printed in the NRC review, citing the EPRI handbook | matrix aluminium 6061B4C wt percent 40basis average, as printed; test temperature and specimen form not stated in Table 2 | — |
| 8 | Elongation to failure, Metamic 15 wt% B4C | Average mechanical properties as printed in the NRC review, citing the EPRI handbook | matrix aluminium 6061B4C wt percent 15basis average, as printed; test temperature and specimen form not stated in Table 2 | — |
| 9 | Elongation to failure, Metamic 31 wt% B4C | Average mechanical properties as printed in the NRC review, citing the EPRI handbook | matrix aluminium 6061B4C wt percent 31basis average, as printed; test temperature and specimen form not stated in Table 2 | — |
| 10 | Elongation to failure, Metamic 40 wt% B4C | Average mechanical properties as printed in the NRC review, citing the EPRI handbook | matrix aluminium 6061B4C wt percent 40basis average, as printed; test temperature and specimen form not stated in Table 2 | — |
| 11 | Yield strength, Al + B4C board (supplier minimum) | Minimum printed in a supplier product table; no test standard named | basis minimum printed as 110 MPa or morecomposition Al + B4C board; matrix alloy not named on the page | — |
| 12 | Tensile strength, Al + B4C board (supplier minimum) | Minimum printed in a supplier product table; no test standard named | basis minimum printed as 200 MPa or more; typical value 300 MPa or more, up to 440 MPa, as printedcomposition Al + B4C board; matrix alloy not named on the page | The page's description section prints a range of 200-440 MPa for the same material. |
| 13 | Elongation after fracture, Al + B4C board (supplier minimum) | Minimum printed in a supplier product table; no test standard named | basis minimum printed as 1.8% or more; typical value 2% to 3% as printedcomposition Al + B4C board; matrix alloy not named on the page | — |
| 14 | Vickers hardness, pristine Al6061 control (113.0 +/- 7.2 Hv as printed) | Vickers hardness with a microhardness tester, as printed in Table 1 | material pristine Al6061 control, no B4Cload 500 gfdwell 10 s | Uncertainty: +/- 7.2 as printed |
| 15 | Vickers hardness, Al6061 with 20 vol% B4C | Vickers hardness with a microhardness tester, as printed in Table 1 | material Al6061 with 20 vol% B4C, stir cast and hot rolledload 500 gfdwell 10 s | Uncertainty: +/- 7.7 as printed |
| 16 | Thermal conductivity, pristine Al6061 at room temperature | Value printed in the text as about 156 W/mK; the composite values are shown only in Figure 7 and are not used | material pristine Al6061 control, no B4Ctemperature room temperaturemeasurement laser flash analyzer | — |
| 17 | Neutron shielding, Al6061 with 50 vol% B4C (indium foil, percent shielded) | Percent shielded as printed in Table 2 (not converted) | B4C vol percent 50matrix Al6061test indium-foil activation with an Am-Be neutron source (4.5 MeV)comparison pristine Al6061 control shielded 1.1 % in the same test | — |
| 18 | Long-term operating temperature, Al + B4C board (supplier limit) | Limit printed in a supplier product table; the NRC review tested Metamic at 398 °C in air for up to 6,139 hours (see corrosion) | basis long-term operating temperature as printed (400℃)composition Al + B4C board | — |
| 19 | Modulus of elasticity, BORAL cermet with 1100 aluminium cladding | Room temperature mechanical properties as printed in Table 3, unit as printed | material BORAL aluminium-B4C cermet core with 1100 aluminium claddingtemperature room temperature | — |
| 20 | Tensile strength, BORAL cermet with 1100 aluminium cladding | Room temperature mechanical properties as printed in Table 3, unit as printed | material BORAL aluminium-B4C cermet core with 1100 aluminium claddingtemperature room temperature | — |
| 21 | Elongation, BORAL cermet with 1100 aluminium cladding | Room temperature mechanical properties as printed in Table 3 | material BORAL aluminium-B4C cermet core with 1100 aluminium claddingtemperature room temperature | — |
| 22 | Compaction density, BORAL cermet core (survey of 40 panels) | Range printed in the NRC review (average 93 percent); cermets do not typically reach theoretical density | material BORAL aluminium-B4C cermet coresample 40 panels surveyed by Brooks and Perkins | Average printed as 93 percent of theoretical density. |
Corrosion and compatibility
What happens when it meets other materials and environments.
| Environment | Concern | What happens |
|---|---|---|
| Simulated BWR water at 90.5 °C (195 °F), mill-finished Metamic | moderate | Mill-finished Metamic lost 3 percent of its weight in BWR water over 9,020 hours, with pitting; anodized Metamic lost none.1 |
| Simulated PWR water (2,500 ppm boron as boric acid) at 90.5 °C, Metamic coupons | low | Mill-finished Metamic showed no measurable weight loss in PWR water.2 |
| Galvanic contact with Inconel 718, 304L stainless steel and Zircaloy 2 | low | Pitting occurred where Metamic was clamped to 304L stainless steel.3 |
| Demineralized BWR water, BORAL aluminium-B4C cermet | low | BORAL corroded at 1.91 mg/cm2/yr (0.28 mil per year), two-sided, in BWR water.4 |
| Air at 398 °C (750 °F) for up to 6,139 hours, plus 2,000 hours more, Metamic coupons | low | No detectable change in Metamic dimensions, density or areal density after long exposure at 398 °C.5 |
| Gamma radiation, 4.5x10^9 to 1.5x10^11 rads, Metamic 15 wt% and 31 wt% | moderate | Gamma doses up to 1.5x10^11 rads changed no dimension, density or hardness, but pitting appeared from 3.6x10^10 rads.6 |
| # | Environment | Details | Test conditions |
|---|---|---|---|
| 1 | Simulated BWR water at 90.5 °C (195 °F), mill-finished Metamic | The 15 wt% mill-finished coupons showed a 3-percent weight loss after 9,020 hours in addition to pitting. Anodized coupons showed no measurable weight loss in either BWR or PWR water. The NRC attributes the pitting in the qualification tests to surface contaminants from manufacturing. | temperature 90.5 °C (195 °F)exposure about 2,000, 4,000, 6,000 and 8,000 hours planned; 9,020 hours reportedtest accelerated general and pitting corrosion, coupons in mill-finished and anodized conditions |
| 2 | Simulated PWR water (2,500 ppm boron as boric acid) at 90.5 °C, Metamic coupons | The NRC reports that PWR coupons showed no detectable weight loss, and that encapsulated coupons showed none in either water after 9,020 hours. Pitting still appeared on some mill-finished coupons, mostly from surface contaminants. | temperature 90.5 °C (195 °F)boron ppm 2500exposure 9,020 hours for encapsulated coupons |
| 3 | Galvanic contact with Inconel 718, 304L stainless steel and Zircaloy 2 | Bimetallic coupons showed localized pitting on mill-finished Metamic, attributed to surface contaminants from extrusion. One anodized 31 wt% coupon clamped to 304L pitted after 9,030 hours, attributed to surface contamination. Galvanic pitting is a known risk when aluminium alloys couple with 304 and 304L stainless steel. | exposure inspected after 4,124 and 9,030 hourscouples Inconel 718, 304L stainless steel, Zircaloy 2 |
| 4 | Demineralized BWR water, BORAL aluminium-B4C cermet | Brooks and Perkins reported a two-sided corrosion rate of 1.91 mg/cm2/yr (0.28 mil per year) for BORAL in BWR water. The NRC expects rates in BWR water to be somewhat higher than in PWR water because of the higher pH without boron. | water demineralized BWR waterproduct BORAL aluminium-B4C cermet |
| 5 | Air at 398 °C (750 °F) for up to 6,139 hours, plus 2,000 hours more, Metamic coupons | After 2,133, 4,124 and 6,139 hours at 398 °C in air, the NRC reports no detectable change in dimensions, density, dry weight or areal density. Tensile properties of 15 wt% coupons stayed within one standard deviation of unexposed coupons. Welded coupons showed lower strength and elongation. | temperature 398 °C (750 °F)atmosphere airexposure 2,133, 4,124 and 6,139 hours, plus 2,000 hours more on the last set |
| 6 | Gamma radiation, 4.5x10^9 to 1.5x10^11 rads, Metamic 15 wt% and 31 wt% | The NRC reports no measurable change in dimension, dry weight, density, B-10 areal density or hardness up to 1.5x10^11 rads, which the NRC equates to about 40 years of fuel-rack exposure. Localized pitting appeared at 3.6x10^10 rads and above. Ultimate tensile strength fell, yield strength rose and elongation fell over the dose range; the NRC calls these changes not significant because the material is not structural. | dose range 4.5x10^9 to 1.5x10^11 rads gammaequivalent exposure about 40 years of fuel-rack exposure at 1.5x10^11 radsfast neutron fluence 5.8x10^19 n/cm2 at the maximum dose |
Risks and side effects
Hazards to people, what happens when a cell overheats, and how the material is handled and stored.
For people
The finished board is a solid metal-matrix material, but machining or grinding it releases B4C dust. The hazard statements we read are for the B4C powder, not the composite.
- Dust
- Cutting, grinding or machining makes fine dust. Use extraction and avoid breathing the dust (SDS statement P261).
- Inhalation
- The powder SDS gives H332 (harmful if inhaled) and H335 (may cause respiratory irritation).
If a part fails
These numbers come from NRC Table 2 and describe average Metamic test results.
- Stretch before breaking
- At 31 wt% B4C, Metamic stretches 2.4 % before it breaks. At 40 wt% it stretches 1.0 %. At 15 wt% it stretches 10.6 %.
- Pitting
- Mill-finished Metamic lost 3 percent of its weight in BWR water over 9,020 hours, with pitting. Anodized Metamic lost none.
Test details
The original wording and numbers from the sources, for readers who want them.
Failure risks
| Failure | Trigger and consequence |
|---|---|
| Loss of ductility at high B4C loadingmoderate severity | Raising Metamic from 31 wt% to 40 wt% B4CElongation to failure fell from 2.4 % at 31 wt% to 1.0 % at 40 wt% (NRC Table 2). |
| Poor bonding of a high-loading cermetmoderate severity | B4C loading above 50 % by weight in the BORAL cermet coreHigher B4C loadings sinter poorly because there is too little aluminium powder, and one BORAL manufacturer limits B4C to 50 percent to keep the cermet bonded to its cladding. |
| Localized pitting from surface contamination or galvanic contactmoderate severity | Mill-finished surfaces in BWR water, or coupling with 304L stainless steelMill-finished Metamic lost 3 percent of its weight in BWR water over 9,020 hours, with pitting (NRC). |
Side effects on surrounding parts
| Affects | Effect |
|---|---|
| Heat paths through the panel | Adding B4C lowers the thermal conductivity of Al6061. NASA reports a gradual decrease with B4C content, against about 156 W/mK for pristine Al6061 at room temperature; the composite values are shown only in a graph. |
Handling and storage
- Machining or grinding the material makes B4C dust. The powder SDS says to avoid breathing dust (P261), and lists H332 and H335. Use extraction at the cutting station.
- Store the boards at 20 ℃ ± 2 ℃ and at or below 10% relative humidity, as the supplier specifies.
- Storage and disposal of the powder: the SDS gives P405 (store locked up) and P501 (dispose of contents under local regulations).
Mitigations
- Anodizing protects Metamic: anodized coupons showed no measurable weight loss in BWR or PWR water, and cleaning before anodizing removes the impurities that cause pitting.
Supply and geography
How common the raw materials are and where they come from.
Aluminium (matrix)
Not read in this run.
- Top producers (2025)
- China 60.8%, India 5.7%, Russia 5.3%, Canada 4.5%, United Arab Emirates 3.6%
- Recycling
- USGS: about 3.6 million tons of aluminium was recovered from purchased scrap in the United States in 2025.
- Substitutes
- USGS: composites, magnesium, steel and titanium can substitute for aluminium in ground transportation uses (the chapter's substitution list).
Boron (feedstock for the B4C particles)
USGS 2026: boron does not occur in nature as an element. It is sold as borates and boric oxide.
- Top producers (2025)
- Turkey
- Critical mineral lists
- US: listed
- Recycling
- Not stated in the USGS boron chapter read.
- Substitutes
- USGS: substitution for boron is possible in detergents, enamels, insulation and soaps. This applies to boron in general, not to B4C.
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.
Show the full YAML
spore: profile
id: aluminium-boron-carbide-composite
spore_version: 0.2
family: aluminium-boron-carbide-composites
name: Aluminium-boron carbide composite (Metamic, BORAL)
abbreviation: Al-B4C
role: neutron absorber for spent-fuel storage racks, transport casks and shields
category: shielding
type: spot-shields
summary: |
Aluminium-boron carbide composite is an aluminium matrix loaded with boron carbide (B4C) particles, which absorb neutrons. The NRC's 2020 review describes Metamic, an aluminium 6061 matrix with 15, 31 or 40 wt% B4C, with a yield strength of 157 MPa at 15 wt% B4C and 207 MPa at 40 wt% B4C. NASA Langley's 2023 ground study of Al6061 with 50 vol% B4C measured 75.5 % shielding of an indium-foil neutron test.
best_for: Neutron absorber panels in spent-fuel pool racks and transport-cask baskets, where boron content matters (NRC 2020; Holtec)
weakest_at: 'Ductility at high B4C loading: elongation falls from 10.6 % at 15 wt% B4C to 1.0 % at 40 wt% (NRC Table 2); no flight data'
identity:
formula: Al + B4C (aluminium matrix with boron carbide particles; Metamic uses an aluminium 6061 matrix)
source: nrc-focht-2020
where: 'Section 4.1 (Metamic: aluminium 6061 matrix with ASTM C-750 Type I B4C particles); supplier mass fraction of B4C 15% to 50% (TRUNNANO product page)'
designations:
- system: Trade name
code: Metamic
source: nrc-focht-2020
where: Section 4.1, Metamic title and first paragraph
tags:
environments: []
stresses:
- total-radiation-dose
applications:
- radiation-shielding
properties:
- benchmark: density
label: Density, Al + B4C board (supplier range)
value: 2.5
value_high: 2.65
bound: range
unit: g/cm3
scope: material
conditions:
composition: Al + B4C, B4C mass fraction 15% to 50% as printed
basis: at least 95% of theoretical density, as printed
form: board, hot rolled or hot isostatic pressed (product page)
method: Range printed in a supplier product table
status: ground
note: The same page's description section prints about 2.5-2.7 g/cm3 for this material; the two ranges are kept as printed.
source: trunnano-b4c-al
where: Main Technical Parameters, Physical properties row
- benchmark: yield_strength
label: Yield strength, Metamic 15 wt% B4C
value: 157
unit: MPa
scope: material
conditions:
matrix: aluminium 6061
B4C_wt_percent: 15
basis: average, as printed; test temperature and specimen form not stated in Table 2
method: Average mechanical properties as printed in the NRC review, citing the EPRI handbook
status: ground
source: nrc-focht-2020
where: Table 2 Average Mechanical Properties of Metamic for Various B4C Loadings, Yield Strength row
- benchmark: yield_strength
label: Yield strength, Metamic 31 wt% B4C
value: 227
unit: MPa
scope: material
conditions:
matrix: aluminium 6061
B4C_wt_percent: 31
basis: average, as printed; test temperature and specimen form not stated in Table 2
method: Average mechanical properties as printed in the NRC review, citing the EPRI handbook
status: ground
source: nrc-focht-2020
where: Table 2, Yield Strength row, 31% column
- benchmark: yield_strength
label: Yield strength, Metamic 40 wt% B4C
value: 207
unit: MPa
scope: material
conditions:
matrix: aluminium 6061
B4C_wt_percent: 40
basis: average, as printed; test temperature and specimen form not stated in Table 2
method: Average mechanical properties as printed in the NRC review, citing the EPRI handbook
status: ground
source: nrc-focht-2020
where: Table 2, Yield Strength row, 40% column
- benchmark: ultimate_tensile_strength
label: Ultimate tensile strength, Metamic 15 wt% B4C
value: 232
unit: MPa
scope: material
conditions:
matrix: aluminium 6061
B4C_wt_percent: 15
basis: average, as printed; test temperature and specimen form not stated in Table 2
method: Average mechanical properties as printed in the NRC review, citing the EPRI handbook
status: ground
source: nrc-focht-2020
where: Table 2, Ultimate Strength row, 15% column
- benchmark: ultimate_tensile_strength
label: Ultimate tensile strength, Metamic 31 wt% B4C
value: 272
unit: MPa
scope: material
conditions:
matrix: aluminium 6061
B4C_wt_percent: 31
basis: average, as printed; test temperature and specimen form not stated in Table 2
method: Average mechanical properties as printed in the NRC review, citing the EPRI handbook
status: ground
source: nrc-focht-2020
where: Table 2, Ultimate Strength row, 31% column
- benchmark: ultimate_tensile_strength
label: Ultimate tensile strength, Metamic 40 wt% B4C
value: 277
unit: MPa
scope: material
conditions:
matrix: aluminium 6061
B4C_wt_percent: 40
basis: average, as printed; test temperature and specimen form not stated in Table 2
method: Average mechanical properties as printed in the NRC review, citing the EPRI handbook
status: ground
source: nrc-focht-2020
where: Table 2, Ultimate Strength row, 40% column
- benchmark: elongation
label: Elongation to failure, Metamic 15 wt% B4C
value: 10.6
unit: '%'
scope: material
conditions:
matrix: aluminium 6061
B4C_wt_percent: 15
basis: average, as printed; test temperature and specimen form not stated in Table 2
method: Average mechanical properties as printed in the NRC review, citing the EPRI handbook
status: ground
source: nrc-focht-2020
where: Table 2, Elongations row, 15% column
- benchmark: elongation
label: Elongation to failure, Metamic 31 wt% B4C
value: 2.4
unit: '%'
scope: material
conditions:
matrix: aluminium 6061
B4C_wt_percent: 31
basis: average, as printed; test temperature and specimen form not stated in Table 2
method: Average mechanical properties as printed in the NRC review, citing the EPRI handbook
status: ground
source: nrc-focht-2020
where: Table 2, Elongations row, 31% column
- benchmark: elongation
label: Elongation to failure, Metamic 40 wt% B4C
value: 1
unit: '%'
scope: material
conditions:
matrix: aluminium 6061
B4C_wt_percent: 40
basis: average, as printed; test temperature and specimen form not stated in Table 2
method: Average mechanical properties as printed in the NRC review, citing the EPRI handbook
status: ground
source: nrc-focht-2020
where: Table 2, Elongations row, 40% column
- benchmark: yield_strength
label: Yield strength, Al + B4C board (supplier minimum)
value: 110
bound: lower
unit: MPa
scope: material
conditions:
basis: minimum printed as 110 MPa or more
composition: Al + B4C board; matrix alloy not named on the page
method: Minimum printed in a supplier product table; no test standard named
status: ground
source: trunnano-b4c-al
where: Main Technical Parameters, Mechanical properties, Yield strength row
- benchmark: ultimate_tensile_strength
label: Tensile strength, Al + B4C board (supplier minimum)
value: 200
bound: lower
unit: MPa
scope: material
conditions:
basis: minimum printed as 200 MPa or more; typical value 300 MPa or more, up to 440 MPa, as printed
composition: Al + B4C board; matrix alloy not named on the page
method: Minimum printed in a supplier product table; no test standard named
status: ground
note: The page's description section prints a range of 200-440 MPa for the same material.
source: trunnano-b4c-al
where: Main Technical Parameters, Mechanical properties, Tensile strength row
- benchmark: elongation
label: Elongation after fracture, Al + B4C board (supplier minimum)
value: 1.8
bound: lower
unit: '%'
scope: material
conditions:
basis: minimum printed as 1.8% or more; typical value 2% to 3% as printed
composition: Al + B4C board; matrix alloy not named on the page
method: Minimum printed in a supplier product table; no test standard named
status: ground
source: trunnano-b4c-al
where: Main Technical Parameters, Mechanical properties, Elongation after fracture row
- benchmark: vickers_hardness
label: Vickers hardness, pristine Al6061 control (113.0 +/- 7.2 Hv as printed)
value: 113
unit: HV
scope: material
conditions:
material: pristine Al6061 control, no B4C
load: 500 gf
dwell: 10 s
method: Vickers hardness with a microhardness tester, as printed in Table 1
status: ground
uncertainty: +/- 7.2 as printed
source: nasa-b4c-al-2023
where: Table 1, Al6061 column
- benchmark: vickers_hardness
label: Vickers hardness, Al6061 with 20 vol% B4C
value: 157.6
unit: HV
scope: material
conditions:
material: Al6061 with 20 vol% B4C, stir cast and hot rolled
load: 500 gf
dwell: 10 s
method: Vickers hardness with a microhardness tester, as printed in Table 1
status: ground
uncertainty: +/- 7.7 as printed
source: nasa-b4c-al-2023
where: Table 1, 20%B4C/Al6061 column
- benchmark: thermal_conductivity
label: Thermal conductivity, pristine Al6061 at room temperature
value: 156
unit: W/mK
scope: material
conditions:
material: pristine Al6061 control, no B4C
temperature: room temperature
measurement: laser flash analyzer
method: Value printed in the text as about 156 W/mK; the composite values are shown only in Figure 7 and are not used
status: ground
source: nasa-b4c-al-2023
where: Section 3 (thermal conductivity paragraph), pristine Al6061 sentence
- benchmark: neutron_shielding_effectiveness
label: Neutron shielding, Al6061 with 50 vol% B4C (indium foil, percent shielded)
value: 75.5
unit: '% shielded'
scope: material
conditions:
B4C_vol_percent: 50
matrix: Al6061
test: indium-foil activation with an Am-Be neutron source (4.5 MeV)
comparison: pristine Al6061 control shielded 1.1 % in the same test
method: Percent shielded as printed in Table 2 (not converted)
status: ground
source: nasa-b4c-al-2023
where: Table 2, row NIA B4C 50% vol, % shielded column
- benchmark: max_service_temp
label: Long-term operating temperature, Al + B4C board (supplier limit)
value: 400
bound: upper
unit: °C
scope: material
conditions:
basis: long-term operating temperature as printed (400℃)
composition: Al + B4C board
method: Limit printed in a supplier product table; the NRC review tested Metamic at 398 °C in air for up to 6,139 hours (see corrosion)
status: ground
source: trunnano-b4c-al
where: Main Technical Parameters, Thermal and shielding performance, long-term operating temperature row
- benchmark: elastic_modulus
label: Modulus of elasticity, BORAL cermet with 1100 aluminium cladding
value: 9
unit: msi
scope: material
conditions:
material: BORAL aluminium-B4C cermet core with 1100 aluminium cladding
temperature: room temperature
method: Room temperature mechanical properties as printed in Table 3, unit as printed
status: ground
source: nrc-focht-2020
where: Table 3 Room Temperature Mechanical Properties of BORAL, Modulus of elasticity row
- benchmark: ultimate_tensile_strength
label: Tensile strength, BORAL cermet with 1100 aluminium cladding
value: 10
unit: ksi
scope: material
conditions:
material: BORAL aluminium-B4C cermet core with 1100 aluminium cladding
temperature: room temperature
method: Room temperature mechanical properties as printed in Table 3, unit as printed
status: ground
source: nrc-focht-2020
where: Table 3 Room Temperature Mechanical Properties of BORAL, Tensile strength row
- benchmark: elongation
label: Elongation, BORAL cermet with 1100 aluminium cladding
value: 0.1
unit: '%'
scope: material
conditions:
material: BORAL aluminium-B4C cermet core with 1100 aluminium cladding
temperature: room temperature
method: Room temperature mechanical properties as printed in Table 3
status: ground
source: nrc-focht-2020
where: Table 3 Room Temperature Mechanical Properties of BORAL, Elongation row
- benchmark: compaction_density
label: Compaction density, BORAL cermet core (survey of 40 panels)
value: 89.5
value_high: 96.1
bound: range
unit: '% of theoretical'
scope: material
conditions:
material: BORAL aluminium-B4C cermet core
sample: 40 panels surveyed by Brooks and Perkins
method: Range printed in the NRC review (average 93 percent); cermets do not typically reach theoretical density
status: ground
note: Average printed as 93 percent of theoretical density.
source: nrc-focht-2020
where: Section 4.3.1 Density and Composition
corrosion:
- environment: Simulated BWR water at 90.5 °C (195 °F), mill-finished Metamic
headline: Mill-finished Metamic lost 3 percent of its weight in BWR water over 9,020 hours, with pitting; anodized Metamic lost none.
effect: The 15 wt% mill-finished coupons showed a 3-percent weight loss after 9,020 hours in addition to pitting. Anodized coupons showed no measurable weight loss in either BWR or PWR water. The NRC attributes the pitting in the qualification tests to surface contaminants from manufacturing.
rating: moderate
conditions:
temperature: 90.5 °C (195 °F)
exposure: about 2,000, 4,000, 6,000 and 8,000 hours planned; 9,020 hours reported
test: accelerated general and pitting corrosion, coupons in mill-finished and anodized conditions
source: nrc-focht-2020
where: Section 4.1.1.5 (Corrosion Testing Results); summary in Section 4.4.1 (general corrosion)
- environment: Simulated PWR water (2,500 ppm boron as boric acid) at 90.5 °C, Metamic coupons
headline: Mill-finished Metamic showed no measurable weight loss in PWR water.
effect: The NRC reports that PWR coupons showed no detectable weight loss, and that encapsulated coupons showed none in either water after 9,020 hours. Pitting still appeared on some mill-finished coupons, mostly from surface contaminants.
rating: low
conditions:
temperature: 90.5 °C (195 °F)
boron_ppm: 2500
exposure: 9,020 hours for encapsulated coupons
source: nrc-focht-2020
where: Section 4.1.1.5 (Corrosion Testing Results); summary in Section 4.4.1.1
- environment: Galvanic contact with Inconel 718, 304L stainless steel and Zircaloy 2
headline: Pitting occurred where Metamic was clamped to 304L stainless steel.
effect: Bimetallic coupons showed localized pitting on mill-finished Metamic, attributed to surface contaminants from extrusion. One anodized 31 wt% coupon clamped to 304L pitted after 9,030 hours, attributed to surface contamination. Galvanic pitting is a known risk when aluminium alloys couple with 304 and 304L stainless steel.
rating: low
conditions:
exposure: inspected after 4,124 and 9,030 hours
couples: Inconel 718, 304L stainless steel, Zircaloy 2
source: nrc-focht-2020
where: Section 4.1.1.5 (Galvanic corrosion paragraph); Section 4.4.1.2 (Pitting)
- environment: Demineralized BWR water, BORAL aluminium-B4C cermet
headline: BORAL corroded at 1.91 mg/cm2/yr (0.28 mil per year), two-sided, in BWR water.
effect: Brooks and Perkins reported a two-sided corrosion rate of 1.91 mg/cm2/yr (0.28 mil per year) for BORAL in BWR water. The NRC expects rates in BWR water to be somewhat higher than in PWR water because of the higher pH without boron.
rating: low
conditions:
water: demineralized BWR water
product: BORAL aluminium-B4C cermet
source: nrc-focht-2020
where: Section 4.4.1.1 (general corrosion, BORAL sentence)
- environment: Air at 398 °C (750 °F) for up to 6,139 hours, plus 2,000 hours more, Metamic coupons
headline: No detectable change in Metamic dimensions, density or areal density after long exposure at 398 °C.
effect: After 2,133, 4,124 and 6,139 hours at 398 °C in air, the NRC reports no detectable change in dimensions, density, dry weight or areal density. Tensile properties of 15 wt% coupons stayed within one standard deviation of unexposed coupons. Welded coupons showed lower strength and elongation.
rating: low
conditions:
temperature: 398 °C (750 °F)
atmosphere: air
exposure: 2,133, 4,124 and 6,139 hours, plus 2,000 hours more on the last set
source: nrc-focht-2020
where: Section 4.1.1.3 (Long-Term Elevated Temperature Testing)
- environment: Gamma radiation, 4.5x10^9 to 1.5x10^11 rads, Metamic 15 wt% and 31 wt%
headline: Gamma doses up to 1.5x10^11 rads changed no dimension, density or hardness, but pitting appeared from 3.6x10^10 rads.
effect: The NRC reports no measurable change in dimension, dry weight, density, B-10 areal density or hardness up to 1.5x10^11 rads, which the NRC equates to about 40 years of fuel-rack exposure. Localized pitting appeared at 3.6x10^10 rads and above. Ultimate tensile strength fell, yield strength rose and elongation fell over the dose range; the NRC calls these changes not significant because the material is not structural.
rating: moderate
conditions:
dose_range: 4.5x10^9 to 1.5x10^11 rads gamma
equivalent_exposure: about 40 years of fuel-rack exposure at 1.5x10^11 rads
fast_neutron_fluence: 5.8x10^19 n/cm2 at the maximum dose
source: nrc-focht-2020
where: Section 4.1.1 (EPRI report summary), radiation exposure paragraph, and Figures 4 and 5
risks:
hazards:
- text: 'Supplier safety data sheet for boron carbide powder (Stanford Advanced Materials, CAS 12069-32-8, revised 10/11/2022): signal word Warning. The powder is harmful if inhaled, causes skin irritation and serious eye irritation, and may cause respiratory irritation. This sheet covers the B4C powder ingredient, not the finished composite.'
ghs:
- H332
- H315
- H319
- H335
source: sds-stanford-b4c
where: Section 2, Hazards identification, Label elements
failure_risks:
- mode: Loss of ductility at high B4C loading
trigger: Raising Metamic from 31 wt% to 40 wt% B4C
consequence: Elongation to failure fell from 2.4 % at 31 wt% to 1.0 % at 40 wt% (NRC Table 2).
severity: moderate
source: nrc-focht-2020
where: Table 2, Elongations row
- mode: Poor bonding of a high-loading cermet
trigger: B4C loading above 50 % by weight in the BORAL cermet core
consequence: Higher B4C loadings sinter poorly because there is too little aluminium powder, and one BORAL manufacturer limits B4C to 50 percent to keep the cermet bonded to its cladding.
severity: moderate
source: nrc-focht-2020
where: Section 3.2 (BORAL, cermet core paragraph)
- mode: Localized pitting from surface contamination or galvanic contact
trigger: Mill-finished surfaces in BWR water, or coupling with 304L stainless steel
consequence: Mill-finished Metamic lost 3 percent of its weight in BWR water over 9,020 hours, with pitting (NRC).
severity: moderate
source: nrc-focht-2020
where: Section 4.1.1.5 (Corrosion Testing Results)
side_effects:
- text: Adding B4C lowers the thermal conductivity of Al6061. NASA reports a gradual decrease with B4C content, against about 156 W/mK for pristine Al6061 at room temperature; the composite values are shown only in a graph.
affects: Heat paths through the panel
source: nasa-b4c-al-2023
where: Results, thermal conductivity paragraph and Figure 7
handling:
- text: Machining or grinding the material makes B4C dust. The powder SDS says to avoid breathing dust (P261), and lists H332 and H335. Use extraction at the cutting station.
source: sds-stanford-b4c
where: Section 2, Hazards identification and precautionary statements (P261)
- text: Store the boards at 20 ℃ ± 2 ℃ and at or below 10% relative humidity, as the supplier specifies.
source: trunnano-b4c-al
where: Description, 6. Instructions for use (storage temperature and relative humidity)
- text: 'Storage and disposal of the powder: the SDS gives P405 (store locked up) and P501 (dispose of contents under local regulations).'
source: sds-stanford-b4c
where: Section 2, Precautionary statements
mitigations:
- text: 'Anodizing protects Metamic: anodized coupons showed no measurable weight loss in BWR or PWR water, and cleaning before anodizing removes the impurities that cause pitting.'
source: nrc-focht-2020
where: Section 4.1.1.5 (Corrosion Testing Results) and summary in Section 4.4.1
uses:
- application: radiation-shielding
device: Neutron absorber panels in spent-fuel pool storage racks (BORAL, Metamic and Boralcan)
example: The NRC reports that BORAL is used in about 60 percent of domestic spent fuel pools, and Metamic and Boralcan together in about 20 percent.
source: nrc-focht-2020
where: Section 1 (Executive Summary) and Section 3.2
- application: radiation-shielding
device: Fuel basket of the HI-STAR 180 transport cask (uses Metamic-HT, a Holtec variant)
example: Holtec cites docket 71-9325 for the HI-STAR 180 transport cask, whose fuel basket uses Metamic-HT, a Holtec variant of Metamic.
source: holtec-metamic
where: Why Metamic? section (docket reference)
- application: radiation-shielding
device: Al6061 plate with 50 vol% B4C for neutron shielding (ground test, not flown)
example: NASA Langley reports that 50 vol% B4C in Al6061 raised neutron shielding effectiveness more than 110 times over pristine Al6061. The study is a ground test with an Am-Be source and a radiation model, not a flight result.
source: nasa-b4c-al-2023
where: Abstract and Table 2
supply:
- subject: Aluminium (matrix)
abundance: Not read in this run.
producers:
- country: China
share_percent: 60.8
year: 2025
- country: India
share_percent: 5.7
year: 2025
- country: Russia
share_percent: 5.3
year: 2025
- country: Canada
share_percent: 4.5
year: 2025
- country: United Arab Emirates
share_percent: 3.6
year: 2025
critical_lists: []
recycling: 'USGS: about 3.6 million tons of aluminium was recovered from purchased scrap in the United States in 2025.'
substitutes:
- 'USGS: composites, magnesium, steel and titanium can substitute for aluminium in ground transportation uses (the chapter''s substitution list).'
source: usgs-mcs2026-aluminum
where: World Smelter Production table, 2025e column (shares calculated by Space Mushroom against the printed world total of 74,000 thousand metric tons, rounded); Recycling; Substitutes
- subject: Boron (feedstock for the B4C particles)
abundance: 'USGS 2026: boron does not occur in nature as an element. It is sold as borates and boric oxide.'
producers:
- country: Turkey
year: 2025
critical_lists:
- list: USGS 2025 Final List of Critical Minerals (boron added in the 2025 list)
listed: true
recycling: Not stated in the USGS boron chapter read.
substitutes:
- 'USGS: substitution for boron is possible in detergents, enamels, insulation and soaps. This applies to boron in general, not to B4C.'
source: usgs-mcs2026-boron
where: 'Events, Trends and Issues (critical minerals paragraph); Production table, Turkey refined borates 2025; Import Sources (2021-24: Turkey 90%); Substitutes'
media: []
documents:
- title: NRC report, Assessment of Aluminum-Based Neutron Absorber Materials Qualification Testing and Surveillance Monitoring Programs (May 2020)
type: report
url: https://www.nrc.gov/docs/ML1935/ML19353A030.pdf
year: 2020
- title: Holtec International, neutron absorber material (Metamic) product page
type: datasheet
url: https://holtecinternational.com/products-and-services/innovative-technologies/neutronabsorbermaterial/
- title: NASA/TM-20230003044, B4C-Al Metal Matrix Composites for Extreme Space Environments
type: report
url: https://ntrs.nasa.gov/citations/20230003044
year: 2023
- title: Luoyang Tongrun Nano (TRUNNANO) product page, Aluminum-based Boron Carbide (Al-B4C) Composite Material, sold as RBOSCHCO
type: datasheet
url: https://www.rboschco.com/products/metals-and-alloys/aluminum-based-boron-carbide-al-b4c-composite-material/
- title: Stanford Advanced Materials safety data sheet, Boron Carbide, CAS 12069-32-8 (revised 10/11/2022)
type: sds
url: https://samaterials.com/tds/1721380172-bc3503.pdf
year: 2022
- title: USGS Mineral Commodity Summaries 2026, Boron
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-boron.pdf
year: 2026
- title: USGS Mineral Commodity Summaries 2026, Aluminum
type: report
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
year: 2026
gaps:
- No manufacturer density value for Metamic was found. The NRC review and the Holtec page give none; the only density is the supplier range of 2.5 to 2.65 g/cm3 for a board whose matrix alloy is not named.
- No elastic modulus, thermal conductivity or coefficient of thermal expansion for Metamic or for the B4C-Al6061 composite was printed as a number in a source read in this run. NASA's tensile values (Figures 5 and 6) and thermal conductivity values (Figure 7) are graphs only and are not used.
- Metamic B-10 areal density specification and neutron absorption cross section were not found in any page read in this run. The NRC text gives the B-10 areal density only as a measured-change result.
- Neutron absorption rate of 90 percent or more (supplier page) names no test standard, composition or thickness, so it is not used as a property.
- The TRUNNANO page names no test standard, test temperature or matrix alloy for its mechanical values. Its description section prints a different density range (about 2.5-2.7 g/cm3) and tensile range (200-440 MPa) from its table; both are recorded.
- Metamic-HT, a Holtec variant with an alumina-reinforced matrix alloy, is a different grade and is not profiled here.
- No flight, vacuum or thermal-vacuum result for the composite was found. The NASA study is a ground neutron test with modelling.
- Atomic weights of boron, carbon and aluminium were not read in a fetched page, so the recipe parts carry no atomic_weight.
- The USGS aluminium chapter read in this run does not state whether aluminium is on a critical-minerals list, so no critical_lists entry is given for aluminium.
- 'Boron carbide production shares were not found: the USGS boron table prints the world total as XX, so no producer shares are calculated for boron.'
- Recycling of boron-carbide composites was not stated in any source read.
- Hazard statements for the finished composite were not found. The SDS read covers the boron carbide powder only.
- Radiation and ageing results give trends and no numeric values for tensile properties after irradiation (the NRC reports the trends in text and in Figures 4 and 5).
- Oxidation and corrosion of the composite in air at high temperature beyond the 398 C exposure were not searched.
- PubChem GHS classification for boron carbide could not be read in this run, because PubChem returned a verification page, so the hazard entry rests on the supplier SDS alone.
- An open-access MDPI Metals paper on B4C/Al6061 composites could not be read in this run (HTTP 403), so its tensile, density and thermal data are not used.
sources:
nrc-focht-2020:
title: 'Assessment of Aluminum-Based Neutron Absorber Materials: Materials Qualification Testing and Surveillance Monitoring Programs (Eric M. Focht, U.S. NRC Office of Nuclear Regulatory Research, May 2020)'
id: NRC ML19353A030
url: https://www.nrc.gov/docs/ML1935/ML19353A030.pdf
year: 2020
kind: report
license: US government work, public domain
holtec-metamic:
title: Holtec International, neutron absorber material (Metamic) product page, Why Metamic? section
url: https://holtecinternational.com/products-and-services/innovative-technologies/neutronabsorbermaterial/
kind: web
license: manufacturer web page, cited not reproduced
nasa-b4c-al-2023:
title: Chu, Park, Wallace, Lum et al. 2023, B4C-Al Metal Matrix Composites for Extreme Space Environments (NASA/TM-20230003044, NASA Langley)
id: NASA/TM-20230003044 (NTRS 20230003044)
url: https://ntrs.nasa.gov/api/citations/20230003044/downloads/NASA-TM-20230003044revised.pdf
year: 2023
kind: report
license: NASA public document
trunnano-b4c-al:
title: Luoyang Tongrun Nano Technology (TRUNNANO), product page, Aluminum-based Boron Carbide (Al-B4C) Composite Material, sold under the RBOSCHCO name
url: https://www.rboschco.com/products/metals-and-alloys/aluminum-based-boron-carbide-al-b4c-composite-material/
kind: web
license: supplier web page, cited not reproduced
sds-stanford-b4c:
title: Stanford Advanced Materials, Safety Data Sheet, Boron Carbide (CAS 12069-32-8), revised 10/11/2022
url: https://samaterials.com/tds/1721380172-bc3503.pdf
year: 2022
kind: datasheet
license: vendor safety data sheet, cited not reproduced
usgs-mcs2026-boron:
title: USGS Mineral Commodity Summaries 2026, Boron
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-boron.pdf
kind: report
license: US government work, public domain
usgs-mcs2026-aluminum:
title: USGS Mineral Commodity Summaries 2026, Aluminum
url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-aluminum.pdf
kind: report
license: US government work, public domain
wikipedia-boron-carbide:
title: Wikipedia, Boron carbide (article read in this run for composition and nuclear use)
url: https://en.wikipedia.org/wiki/Boron_carbide
kind: web
license: CC BY-SA 4.0, cited not reproduced
license: CC-BY-4.0
updated: '2026-11-01'
review:
status: draft
method: assistant
checked_values: 22
unreachable: 13
caveats: 4
note: 'Written in this run from pages and PDFs read in this run: NRC 2020 (PDF, read as text), NASA/TM-20230003044 (PDF, read as text), the Holtec product page, the TRUNNANO product page, the Stanford boron carbide SDS (PDF), and the USGS MCS 2026 boron and aluminum chapters (PDF). verify-values found 9 of 22 values in their source text and 0 not found. The 13 NRC values (Table 2, Table 3 and the compaction density range) could not be fetched by the script, because nrc.gov returns HTTP 403 to scripted requests; they were read by hand from the same PDF in this run. Supplier values are unverified manufacturer or reseller claims with no test standard named. NASA tensile and thermal conductivity values appear only in figures and are not used. The Wikipedia boron carbide article was read in this run for the composition and nuclear-use sentence in the recipe.'
story:
recipe:
line: 'Aluminium-boron carbide composite is an aluminium matrix that holds boron carbide (B4C) particles. Wikipedia notes that boron carbide absorbs neutrons without forming long-lived radionuclides, which is why it is used in nuclear shielding. Metamic is made by powder metallurgy from high-purity aluminium powder and nuclear grade boron carbide (ASTM C750 Type 1), per Holtec, then extruded into preforms and hot rolled to final thickness (NRC). BORAL is a different form: a cermet core of B4C and aluminium powder in 1100 aluminium cladding, hot rolled into plate or sheet (NRC).'
parts:
- name: Aluminium
symbol: Al
role: The matrix. Metamic uses aluminium 6061; the BORAL core uses 1100 aluminium powder and cladding. It holds the particles and carries the load.
share_note: balance (the rest of the mass)
source: nrc-focht-2020
where: Section 3.2 and Section 4.1
- name: Boron carbide
symbol: B4C
role: The neutron absorber. Boron captures neutrons, so the B4C content sets how much neutron absorption the panel gives.
share_percent: 15
share_high: 50
source: trunnano-b4c-al
where: Main Technical Parameters, Material composition (mass fraction 15% to 50%)
risk_groups:
- title: For people
level: 1
verdict: Dust hazard when machining
lead: The finished board is a solid metal-matrix material, but machining or grinding it releases B4C dust. The hazard statements we read are for the B4C powder, not the composite.
points:
- label: Dust
line: Cutting, grinding or machining makes fine dust. Use extraction and avoid breathing the dust (SDS statement P261).
- label: Inhalation
line: The powder SDS gives H332 (harmful if inhaled) and H335 (may cause respiratory irritation).
- title: If a part fails
level: 2
verdict: Ductility falls as B4C rises
lead: These numbers come from NRC Table 2 and describe average Metamic test results.
points:
- label: Stretch before breaking
line: At 31 wt% B4C, Metamic stretches 2.4 % before it breaks. At 40 wt% it stretches 1.0 %. At 15 wt% it stretches 10.6 %.
- label: Pitting
line: Mill-finished Metamic lost 3 percent of its weight in BWR water over 9,020 hours, with pitting. Anodized Metamic lost none.
why: Aluminium-boron carbide composite puts boron carbide particles into an aluminium matrix, so a structural-looking panel can also absorb neutrons. Metamic and BORAL are the two products the NRC reviewed for spent-fuel storage. NASA Langley tested an aluminium 6061 version with boron carbide for space radiation shielding in a ground study. The composite is chosen when neutron absorption has to be built into the material, not added as a separate shield.
uses:
- where: Spent fuel pool racks
line: The NRC reports that BORAL is used in about 60 percent of US spent fuel pools, and Metamic and Boralcan together in about 20 percent.
- where: Transport cask fuel basket
line: Holtec cites docket 71-9325 for the HI-STAR 180 transport cask, whose fuel basket uses Metamic-HT, a Holtec variant.
- where: Ground test for space radiation
line: NASA Langley tested Al6061 with 50 vol% B4C in a ground neutron test, and its model suggests it also helps against galactic cosmic rays. It is not a flight result.
can_do:
- label: Neutron absorption
benchmark: neutron_shielding_effectiveness
line: At 50 vol% B4C in Al6061, NASA measured 75.5 % shielded in an indium-foil neutron test. NASA reports a shielding effectiveness more than 110 times that of pristine Al6061.
- label: Yield strength
benchmark: yield_strength
line: Metamic averages a yield strength of 157 MPa at 15 wt% B4C and 227 MPa at 31 wt% B4C, according to NRC Table 2.
- label: Hardness
benchmark: vickers_hardness
line: NASA measured 157.6 Hv for Al6061 with 20 vol% B4C, against 113.0 Hv for pristine Al6061.
- label: Temperature limit
benchmark: max_service_temp
value: 400 °C
line: The supplier gives a long-term operating limit of 400 °C for its board.
compare: 'Compared with pristine Al6061, B4C raises hardness and lowers thermal conductivity. NASA reports Vickers hardness of 157.6 Hv at 20 vol% B4C against 113.0 Hv for pristine Al6061, and about 156 W/mK for pristine Al6061 at room temperature, with the composite values shown only in a figure. Within the Metamic loadings, more B4C means less stretch: elongation is 10.6 % at 15 wt% and 1.0 % at 40 wt%, while yield strength is 157 MPa at 15 wt% and 207 MPa at 40 wt%.'
compare_rows:
- label: Density
benchmark: density
- label: Yield strength
benchmark: yield_strength
- label: Thermal conductivity
benchmark: thermal_conductivity
handling:
- Machining or grinding the material makes B4C dust. Use extraction and avoid breathing the dust (SDS statement P261).
- Store the boards at 20 ℃ ± 2 ℃ and at or below 10% relative humidity, as the supplier specifies.
- 'Expect little stretch at high loading: the 40 wt% grade elongates 1.0 % before it fails.'
good_for:
- Neutron absorption in spent fuel racks. NRC reports BORAL in about 60 percent of US spent fuel pools.
- Neutron absorption with some strength. Metamic at 15 wt% B4C has a yield strength of 157 MPa and 10.6 % elongation.
watch_out:
- 'Ductility falls with B4C content: 2.4 % elongation at 31 wt% and 1.0 % at 40 wt%.'
- Pitting in BWR water and in galvanic contact with 304L stainless steel. Anodizing helps.
- No flight data. The NASA result is a ground neutron test and a model.
verdict: The composite is an established neutron absorber in nuclear storage, backed by the NRC's 2020 review of qualification tests. Its space role rests on one NASA ground study. Density is a supplier range, and the Metamic tensile values are averages, so confirm the grade and loading before using any number.
References
Every number above carries a reference number. Click one to see the source and where in it the value comes from.
Updated