The influence of microstructural characteristics on yield point elongation phenomenon in Fe-0.2C-11Mn-2Al steel

We elucidate here the underlying reasons for the yield point elongation (YPE) phenomenon in medium-Mn steel. The cold-rolled Fe-0.2C-11Mn-2Al steel was subjected to controlled annealing temperature and soaking time such that YPE of different lengths was obtained. It was observed that the ultra-fine grained or globular microstructure is not the critical factor responsible for YPE. YPE is a consequence of close competition between the work hardening (via martensitic transformation) and softening (by stress relaxation and transfer) induced by the TRIP effect. The ferrite grains with γ fiber have the potential to have high dislocation storage ability, with consequent increase in dislocation density and work hardening exponent, leading to decrease of YPE.