Strain hardening exponent

The strain hardening exponent (also called strain hardening index), noted as n, is a material's constant which is used in calculations for stress–strain behavior in work hardening.

In the formula σ = K ε ⁿ,
σ represents the applied stress on the material,
ε is the strain,
K is the strength coefficient.

The value of the strain hardening exponent lies between 0 and 1. A value of 0 means that a material is a perfectly plastic solid, while a value of 1 represents a 100% elastic solid. Most metals have an n value between 0.10 and 0.50.

Tabulation

Tabulation of n and K Values for Several Alloys ^[1]

Material	n	K (MPa)
Low-carbon steel (annealed)	0.21	600
4340 steel alloy (tempered @ 315 °C)	0.12	2650
304 stainless steel (annealed)	0.43	1400
Copper (annealed)	0.44	530
Naval brass (annealed)	0.21	585
2024 aluminum alloy (heat treated—T3)	0.17	780
AZ-31B magnesium alloy (annealed)	0.16	450

References

1. Callister, Jr., William D (2005), Fundamentals of Materials Science and Engineering (2nd ed.), United States of America: John Wiley & Sons, p. 199, ISBN 978-0-471-47014-4

External links

• More complete picture about the strain hardening exponent in the stress–strain curve on www.key-to-steel.com