Effect of thermo-mechanical cycling on the microstructure and strength of lath martensite in the weld CGHAZ of HSLA steel

This work has investigated the effect of thermo-mechanical cycling on the microstructure and strength of lath martensite in the weld Coarse Grained Heat Affected Zone (CGHAZ). The weld CGHAZ was simulated by Gleeble simulator according to the thermal cycle calculated by Rosenthal equation. The results show clearly that deformation promotes the dislocation density during cooling and thus decreases the width of lath martensite in the weld CGHAZ. In addition, the fraction of particle increased in the deformed weld HAZ and this is because the precipitation kinetics is accelerated by deformation. Meanwhile, lath martensite strength in deformed CGHAZ was a higher than undeformed CGHAZ, which is due to the contribution of grain boundary strengthening and precipitation strengthening.