LAUSR

Abstract In this study, to further understand the effect of microstructure on the third type strain ageing (3rd SA) phenomenon, three kinds of heat treatments were conducted on cold-rolled DH-36 structural steel. The microstructures of the heat-treated specimens were observed using scanning electron microscope and compared with the as-received microstructure. The influences of heat treatment on the 3rd SA effect were analyzed. Through the analysis of the previous experimental results of DH-36 steel and Q235B steel, stress peak in the flow stress vs. temperature curves caused by the 3rd SA effect was observed at each of the indicated strain rates for the two steels. As strain rate increases, the stress peak shifts to higher temperature range. Based on the mechanism of the 3rd SA effect, e.g. the interaction of moving dislocations and diffusing solute atoms, a model was developed to quantitatively describe the strain rate effect on the 3rd SA effect.