Effects of aging heat-treatment on dynamic strain aging behavior in high-Mn lightweight steel

Abstract

High-Mn lightweight steel, Fe-0.9C-30Mn-8Al, was subjected to systematic examination to investigate the effects of aging heat-treatment on mechanical properties and tensile behavior as a function of test temperature from 25 to 425 °C and strain rate of 3.33 × 10−4, 3.33 × 10−3 and 3.33 × 10−2 s−1. Peak in the flow stress, plateau of yield strength and ultimate tensile strength as well as negative strain rate sensitivity (SRS) were observed in the steel during tensile test, which are obvious evidences of dynamic strain aging (DSA) behavior. The dislocation line bent by the dislocation-solute interaction in the as-quenched and the aged specimens was also observed by transmission election microscopy (TEM). κ-carbide precipitated within grain and on grain boundary during aging heat-treatment improved yield strength and ultimate tensile strength and reduced percentage elongation to fracture; however, the precipitated κ-carbide reduced the stress difference (Δσ) with strain interval (Δε) in stress-strain curves when DSA occurred in the steel. The activation energy for solute migration was calculated with McCormick's equation to measuring the critical strain for the onset of serration as a function of test temperature and strain rate.