Study on elastic constant softening in stress-induced martensitic transformation by molecular dynamics simulation

Precursor phenomena are critical issues for martensitic transformation, as they provide important clues for understanding the origin of the transformation and the structure of transformation products. Prior to temperature-induced martensitic transformation, it has been widely recognized for a long time that the basal plane shear modulus C′ (=(C11 − C12)/2) of the parent phase decreases with approaching transformation temperature. On the other hand, martensitic transformation can also be induced by stress. But little is known about whether similar precursor phenomenon also exists prior to such a stress-induced martensitic transformation (SIM). In the present study, we used molecular dynamics method to simulate the precursory stage of a stress-induced martensitic transformation. A new method for calculating the elastic constants C′ prior to SIM was proposed. The relationship between C′ and applied stress at different temperatures was calculated. Our results showed that the softening of elastic constant C′ is a common feature for both temperature and stress-induced martensitic transformation. For stress-induced martensitic transformation, the critical stress to induce the transformation increases with increasing temperature and obey Clausius–Clapyeyron relationship; at a given temperature, C′ decreases with the applied stress approaching the critical stress.