Deformation twinning was observed in numerous engineering and naturally occurring materials. However, a fundamental law for critical twinning stress had not yet emerged. This long-standing issue was resolved by integrating twin-energy pathways obtained via ab initio density functional theory with heterogeneous, dislocation-based twin nucleation models. Via an hierarchical theory, an analytical expression was established that quantitatively predicted the critical twinning stress in face-centred cubic metals without any empiricism at any length-scale. The theory predicted a monotonic relation between the unstable twin stacking fault energy and twin nucleation stress revealing the physics of twinning.

Predicting Twinning Stress in FCC Metals - Linking Twin-Energy Pathways to Twin Nucleation. S.Kibey, J.B.Liu, D.D.Johnson, H.Sehitoglu: Acta Materialia, 2007, 55[20], 6843-51