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Thermal Expansion Coefficient and Young's Modulus by Material

Parts do not stay the size they were measured at. This table gives the typical linear thermal expansion coefficient and Young's modulus of common shop materials, so you can estimate how much a part grows or flexes before you set a tolerance or an inspection temperature.

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MaterialFamilyCTE (um/m per K)Young's modulus (GPa)Growth, mm per m per 100 K
Carbon steel 1018
Steel
11.7
205
1.17
Alloy steel 4140
Steel
12.3
205
1.23
Stainless 304
Stainless
17.2
193
1.72
Stainless 316
Stainless
16
193
1.6
Stainless 410
Stainless
9.9
200
0.99
Stainless 17-4 PH
Stainless
10.8
197
1.08
Gray cast iron
Steel
10.5
100
1.05
Aluminium 6061-T6
Aluminium
23.6
68.9
2.36
Aluminium 7075-T6
Aluminium
23.4
71.7
2.34
Aluminium 2024-T3
Aluminium
23.2
73.1
2.32
Copper C11000
Copper alloy
17
117
1.7
Brass C36000
Copper alloy
20.5
97
2.05
Phosphor bronze C51000
Copper alloy
17.8
110
1.78
Titanium Ti-6Al-4V
Titanium
8.6
114
0.86
Inconel 718
Nickel alloy
13
200
1.3
Nickel 200
Nickel alloy
13.3
204
1.33
Invar 36
Nickel alloy
1.3
141
0.13
Magnesium AZ31B
Other metal
26
45
2.6
Zinc (pure)
Other metal
30
108
3
Tungsten
Other metal
4.5
411
0.45
Borosilicate glass
Glass
3.3
64
0.33
Acetal (POM)
Plastic
110
3
11
Nylon 6/6
Plastic
80
2.8
8
Polycarbonate
Plastic
65
2.4
6.5
ABS
Plastic
90
2.3
9
PTFE
Plastic
120
0.5
12

Values are typical room-temperature to about 100 degrees C figures from common handbook data. Real values vary with alloy, temper, temperature range and, for plastics, fillers, moisture and grade. Use the supplier data sheet for any tolerance-critical calculation.

Link material data to inspection records

We can discuss how to connect material attributes with inspection results in your ERP or quality system.

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How to use the table

Find your material, then multiply its CTE by the length and the temperature change. Growth in micrometres equals CTE in um/m per K times length in metres times temperature change in K. The last column does that for one metre and a 100 K rise, in millimetres, so you can scale it quickly. Young's modulus helps estimate deflection and stress when a constrained part cannot expand. Export to Excel to link the values to a quote or a tolerance study.

Where it matters in a plant

Dimensional inspection is standardised at 20 degrees C, so a warm aluminium part measured at 30 degrees C reads larger than it really is. Mixed-material assemblies, such as an aluminium housing with a steel shaft or a plastic part on a metal frame, see differential growth that changes fits and seal loads. Machine tools and fixtures drift as the shop warms during a shift, which shows up as size trends in the SPC chart.

  • 100 mm aluminium part, 10 K warmer: about 0.024 mm larger
  • Steel and aluminium differ by roughly a factor of two
  • Plastics expand five to ten times more than steel
  • Invar is used where size stability beats cost

Common mistakes

People often use a single steel value for all steels, although stainless 304 expands almost one and a half times as much as carbon steel. Another error is using the room-temperature CTE for a wide temperature span, where the coefficient rises. Finally, many forget that plastics absorb moisture and swell, which adds to thermal change. For critical work, measure at a controlled temperature rather than correcting by calculation.

Frequently Asked Questions

What is the CTE of aluminium compared to steel?

Aluminium 6061 is about 23.6 um/m per K, roughly twice carbon steel at about 11.7. A one metre aluminium bar warms and grows about 0.24 mm for a 10 K rise, against 0.12 mm for steel.

How do I calculate thermal growth?

Change in length equals CTE times original length times temperature change. With CTE in um/m per K, length in m and temperature in K, the result is in micrometres. Divide by 1000 for millimetres.

Why is Invar listed?

Invar 36 has an unusually low expansion near room temperature, about 1.3 um/m per K, so it is used for gauges, moulds and optical or measurement fixtures where dimensional stability matters more than strength or cost.

Are the plastic values reliable?

They are only typical. Fillers such as glass fibre can cut expansion a lot, and grades, moisture and temperature change the result. Use the resin supplier data sheet for design work.

If you want measured sizes, inspection temperatures and material data to sit together in your quality records, we can help wire that up from your ERP and inspection data.

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