Effect of Strain Aging on Yield Strength and Strain Hardening Rate of Dual Phase Steel and High Strength Low Alloy Steel

The effect of strain aging on yield strength and strain hardening rate of a dual phase steel and a high strength low alloy (HSLA) steel was studied by mechanical properties test and microstructure observation. The results show that the yield strength of the dual phase steel and the HSLA steel increased by 106 MPa and 28 MPa after 2% pre-strain. After pre-strain and bake, the yield strength of dual phase steel increased by 149 MPa, while yield strength of HSLA steel increased by 66 MPa only. After pre-strain or bake hardening, the strain hardening rate of both steels dropped, but the dual phase steel still had very high strain hardening ability close to the strain hardening rate of HSLA steel without pre-strain. It was ferrire-martensite that made the dual phase steel had higher strain hardening ability than the HSLA steel.