WORK SOFTENING IN SHOCK-LOADED NICKEL

It is shown that nickel shock loaded to a pressure of 20 GN/m**2 (200 Kbar) and pulse durations of 1. 2, 2. 4, and 10. 1 mu sec exhibits work softening upon subsequent uniaxial tensile deformation at room temperature and nominal strain rate of 10** minus **4 sec** minus **1. When the tensile deformation on the preshocked sample is conducted at 77 K, work softening is inhibited. It is proposed, in accordance with the findings of others that work softening is due to dynamics recovery which during conventional deformation replaces the shock-loading substruccture (small cells, with ill-defined walls) by the substructure characteristic of the conventional deformation at the imposed conditions. Since the quasistatic deformation substructure at 77 K is similar to the shock-induced one, work softening is inhibited at that temperature.