Resistance and thermocouple alloys

resistance-and-thermocouple-alloys

8 materials across 3 types

About resistance and thermocouple alloys

Resistance and thermocouple alloys (nichrome, constantan, manganin, Alumel, Chromel, Evanohm, Fecralloy): resistivity, temperature coefficient and temperature limit with sources.

These alloys are chosen for their electrical behaviour. Resistance alloys heat or measure current steadily, and thermocouple alloys produce a voltage that depends on temperature.

Their resistivity and temperature coefficient matter more than strength, and each page lists them with the standard or datasheet they come from.

At a glance

Highest density: Constantan (CuNi) reaches 8.9 g/cm³. Lowest: Fecralloy (Fe-Cr-Al-Y) starts at 7.22 g/cm³. (8 of 8 grades have a sourced value.)
Highest melting point: Thermocouple wire alloys (TC) reaches 1,535 °C. Lowest: Manganin (CuMn12Ni) starts at 960 °C. (8 of 8 grades have a sourced value.)
Highest electrical resistivity: Evanohm reaches 0.0000013 Ω·m. Lowest: Thermocouple wire alloys (TC) starts at 1.2e-7 Ω·m. (8 of 8 grades have a sourced value.)

Ranges run across the conditions each source reports (temper, heat treatment, form), measured at room temperature where the source says so.

How they compare

The same measurements for every material in the collection. A range means the grade has values under several conditions; "at least" means the source gives a specified minimum. "no data" means no sourced value yet. For ranked tables, open a benchmark.

Resistance and thermocouple alloys: how the grades compare
Material	Density	Melting point	Electrical resistivity	Thermal conductivity	Young's modulus	Thermal expansion
Nichrome (NiCr 80/20)resistance heating alloy	8.3 to 8.4 g/cm³	1,400 °C	0.0000011 Ω·m	15 W/(m·K)	no data	14.1 to 17.2 ppm/K
Constantan (CuNi)precision resistance alloy and thermocouple leg	8.9 g/cm³	1,225 to 1,300 °C	5.2e-7 Ω·m	19.5 to 21.2 W/(m·K)	162 to 165 GPa	14.5 to 14.9 ppm/K
Manganin (CuMn12Ni)precision resistance alloy for standards, shunts and gauges	8.4 g/cm³	960 °C	4.3e-7 to 4.8e-7 Ω·m	22 W/(m·K)	124 to 159 GPa	14 to 19.5 ppm/K
Alumel (KN)negative leg of the Type K thermocouple	8.6 to 8.61 g/cm³	1,399 °C	2.9e-7 Ω·m	29.7 W/(m·K)	no data	12 ppm/K
Chromelpositive leg of Type K and Type E thermocouples	8.72 to 8.73 g/cm³	1,427 to 1,430 °C	7.1e-7 Ω·m	19.2 W/(m·K)	200 GPa	13.1 to 17 ppm/K
Evanohmprecision resistance alloy	8.1 g/cm³	1,340 to 1,390 °C	0.0000013 Ω·m	14.6 W/(m·K)	221 GPa	11.7 to 13 ppm/K
Fecralloy (Fe-Cr-Al-Y)resistance heating and catalyst-substrate alloy	7.22 g/cm³	1,380 to 1,490 °C	0.0000013 Ω·m	16 W/(m·K)	no data	11.1 ppm/K
Thermocouple wire alloys (TC)positive and negative legs of base-metal thermocouples	7.86 to 8.9 g/cm³	1,083 to 1,535 °C	1.2e-7 to 7.1e-7 Ω·m	81 to 391 W/(m·K)	117 GPa	17.6 ppm/K

What these materials are made of

Composition by weight, as printed in the sources for each grade (the first constituents listed).

Composition of each grade
Material	Main constituents
Nichrome (NiCr 80/20)	Ni 80% · Cr 20%
Alumel (KN)	Ni 95% · Mn 2% · Al 2% · Si 1%
Chromel	Ni 90% · Cr 10%
Evanohm	Ni 73.5% · Cr 20% · Al 2.5% · Cu 2% · Mn 1% · Si 1%
Fecralloy (Fe-Cr-Al-Y)	Fe 72.8% · Cr 22% · Al 5% · Y 0.1% · Zr 0.1%

Where they are used

Uses
Use	Grades
Resistance heating elements	Nichrome (NiCr 80/20), Fecralloy (Fe-Cr-Al-Y)
Precision wire-wound resistors	Nichrome (NiCr 80/20)
Burn-wire release actuator for a CubeSat tie-down	Nichrome (NiCr 80/20)
Precision and shunt resistors, and measuring resistors	Constantan (CuNi)
Thermocouple leg (copper-nickel or iron pairing) for temperature measurement	Constantan (CuNi)
Strain gauge grids and multipurpose instrumentation cable	Constantan (CuNi)
Precision standard resistors (US legal ohm)	Manganin (CuMn12Ni)
Precision, standard and shunt resistors	Manganin (CuMn12Ni)
Foil pressure gauges for shock-wave and high-pressure studies	Manganin (CuMn12Ni)
Type K (chromel-alumel) thermocouple sensor	Alumel (KN)
Sheathed micro-miniature Type K thermocouple probe for thermal protection system measurement	Alumel (KN)
Type K thermocouple, positive leg	Chromel
Type E thermocouple, positive conductor	Chromel
Strain gauges	Evanohm
Precision resistors	Evanohm
Precision current-sense resistors in measurement instruments	Evanohm

When each grade fits

Best use and weak spots of each grade
Material	Best for	Weakest at
Nichrome (NiCr 80/20)	Carrying current as a heater: 1.09 Ohm mm2/m resistivity with a continuous limit of 1200 °C in air, and a chromium oxide scale that resists oxidation	Strength at temperature: 15 MPa for 1 % creep in 1000 h at 800 °C and 4 MPa at 1000 °C, and a thermal conductivity of only 15 W/(m·K)
Constantan (CuNi)	Precision resistors, strain gauges and thermocouple legs that need a resistance which stays nearly constant with temperature, up to about 600 °C	Conduction and heat flow: resistivity of 52 µΩ·cm (Goodfellow) and thermal conductivity of 21.2 W/(m·K) (Matthey) make it a resistor alloy, not a conductor. Nickel content also brings a skin-sensitisation hazard (H317 on the nickel SDS).
Manganin (CuMn12Ni)	Precision resistors, resistance standards and current shunts whose resistance must stay nearly constant near room temperature: about ±10 ppm/K between 20 and 50 °C	Heat and humidity: the supplier limits precision resistors to 60 °C and gives 140 °C as the maximum in air (Goodfellow prints 300 °C), and NIST shows that an unsealed winding drifts with atmospheric humidity.
Alumel (KN)	Negative leg of a base-metal thermocouple used in oxidising or neutral air, where the Chromel/Alumel pair is printed to 1260 °C, with a melting point of 1399 °C and a resistivity of 29.4 µΩ·cm at 20 °C	Low-oxygen and sulphur exposure of the Type K pair: Pyromation reports green rot in the chromel leg and large negative drift between 816 and 1038 °C, and failure on sulphur exposure
Chromel	Sensing temperature as the positive leg of a base-metal thermocouple across about -200 °C to 1260 °C, with a chromium oxide scale that keeps it stable in air (Concept Alloys)	Use in reducing, alternating or vacuum atmospheres, which Kanthal excludes, and the sources give no corrosion rate; the mechanical data are only room-temperature and 500 °C points
Evanohm	Precision and strain-gauge resistors: a temperature coefficient of about ±10 ppm/°C with 133 µΩ·cm resistivity, and very low thermal EMF against copper (1.0 µV/°C)	Heat and load: Goodfellow gives 300 °C maximum use in air and no oxidation rate, and the annealed strip has a yield strength of only 300 MPa minimum
Fecralloy (Fe-Cr-Al-Y)	Heating elements in air at high temperature, where the printed 1100 to 1300 °C use range and the alumina scale are the main reasons to choose it	Strength at temperature: Goodfellow says only that strength is good up to 1000 °C, and no creep data for this grade were found
Thermocouple wire alloys (TC)	Base-metal temperature sensing where the pair is chosen by range and atmosphere (Type N for stable readings in air above 1000 °C, per Kanthal)	Each pair is limited by its atmosphere: the iron leg rusts, sulphur attacks the iron and Nisil legs, and Nicrosil cannot be used in vacuum or reducing gas (Kanthal, Isabellenhutte, Pyromation)