Lattice Defects in Shock-Deformed and Cold-Worked Nickel

Abstract

For equivalent values of plastic strain, the dislocation density and point‐defect concentration following deformation by the propagation of high‐amplitude shock waves (70 to 330 kbar) through high‐purity polycrystalline nickel are appreciably larger than as a result of cold rolling near 0°C. Based on the electrical‐resistivity change in recovery state III and IV, it is concluded that vacancies rather than interstitials are the predominant point defects formed. The ratio of the two types of defects that are formed appears to be essentially strain‐rate independent. The dominant point‐defect formation mechanism is believed to consist of the nonconservative motion of jogs on screw (or mixed‐character) dislocations. The observed enhanced formation of point defects as a result of shock deformation is explained as the result of the increasing efficiency of this process with increasing dislocation velocity.