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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.

Electron backscatter diffraction has been used to study the severe plastic deformation occurring in the surface layer of an AISI 316L stainless steel treated by high-current pulsed electron beam (HCPEB). The exact nature of the triggered mechanisms was orientation-dependent. In particular, twinning was activated in grains having 〈1 1 1〉 orientation close to the sample normal direction while high misorientation deformation gradients were created by intense crystallograplic slip in some other grains. The nature of the different deformation mechanisms and their orientation dependence are discussed both from theoretical and experimental points of views by considering the biaxial quasi-static thermal stresses generated during the HCPEB bombardment.