Competition between slip and twinning in face-centered cubic metals

Abstract

A criterion is proposed to predict the transition from slip to twinning in the face-centered cubic (FCC) metals within the framework of the generalized stacking fault energy (GSFE) curves, which are calculated by using the full potential linearly augmented plane wave method incorporating local orbital based on density functional theory. The criterion is a function of the stacking fault energy, unstable stacking fault energy, and unstable twinning fault energy, which are obtained from the GSFE curves. Based on the competition between slip and twinning, a new parameter is proposed to rank the sequence of the twinnability for ten typical FCC metals. The ranking results are in good agreement with the experimental data available. Compared with the previous studies of heterogeneous nucleation of twin, it is found that the heterogeneous nucleation sites of twinning such as crack tip and grain boundary do not change the ranking sequence. It is suggested that the GSFE curve may be regarded as the dominant factor determining the twinnability of FCC metals.