It was found that shock-wave deformation, to a pressure of 45GPa for a duration of 1.8μs, produced extensive twinning. The subsequent mechanical response was significantly affected, in that the shock-hardening exceeded the hardening that was expected to arise from the transient shock strain. The enhanced hardening, and other alterations in response, were attributed to barriers (to plastic deformation) that were presented by the deformation twins. A model was proposed that predicted a threshold shock stress for mechanical twinning. It was based upon the application of the Swegle-Grady relationship, between shock stress and strain rate, to constitutive equations which described the critical stress for slip and twinning. The model incorporated grain-size effects, and predicted a threshold twinning stress that was a function of temperature and grain size. The predictions of the model were in qualitative agreement with experimental data.

L.E.Murr, M.A.Meyers, C.S.Niou, Y.J.Chen, S.Pappu, C.Kennedy: Acta Materialia, 1997, 45[1], 157-75