Effect of hot deformation of austenite on martensitic transformation in high manganese steel

The effect of hot deformation of austenite (compressed by 70% at 1023 K) on the martensitic transformation was studied using scanning electron microscopy and electron backscattering diffraction to obtain better control of the transformation- and twinning-induced plasticity effect on high manganese steels with very low carbon content at room temperature. The results show that hot deformation hindered the martensitic transformation, and the amounts of the two kinds of martensite (ε-M and α’-M) significantly decreased. The recovery treatment weakened the mechanical stabilization of the austenite, and the martensite content increased, especially for ε-M. The martensitic transformation was the most difficult in the dynamically recrystallized grains because of the effects of high density defects and small size. The martensitic transformation of deformed grains, particularly near the grain boundaries, were the next most difficult. The statically recrystallized grains exerted the least resistance to transformation, especially when they grew into large sizes. The strong variant selection occurred in two steps (γ → ε-M and ε-M → α′-M). A tilted basal texture in ε-M was formed because of the austenite deformation, whereas both the ε-M texture and strain energy influenced the texture in α′-M. However, the recovery effect still weakened the variant selection.

► Effect of hot-deformed austenite on martensitic transformation (MT) in micro scale.
► Behaviors of grain size, orientation and orientation gradients of austenite for MT.
► Determination of different transformation behavior of two types of martensite.
► Orientation distribution and variant selection of two types of martensite.
► Extent of relieving the resistance to MT by recovery treatment.