Effect of vacancy clusters on yielding and strain hardening of copper

Abstract

Clustering of excess vacancies in copper single crystal specimens was followed by resistivity, x-ray small angle scattering, and stress—strain curve observations. No change in yield stress or strain hardening rate was associated with excess vacancies when they existed primarily as single vacancies, divacancies or perhaps slightly larger aggregates. An increase in the critical resolved shear stress at the yield that was independent of the orientation of the tensile axis accompanied the growth of vacancy clusters in the size range 10 Å to 30 Å. Larger clusters also were associated with orientation dependent changes in the strain hardening characteristics.