Orientation dependence of energy dissipation during plastic deformation of f.c.c. crystals

Abstract

Aluminium polycrystals and aluminium and silver crystals of 〈111〉, 〈110〉, 〈100〉 and m=0·5 orientations were deformed rapidly in compression in a vacuum chamber. The dissipated energy was calculated from the temperature rise during adiabatic compression. The total dissipated energy as a function of shear strain was approximately the same for all orientations including the polycrystals. The ratio of dissipated energy to the total work done on the specimen at various strains was also very similar for all orientations except for the aluminium 〈100〉 crystals. The aluminium 〈100〉 crystals dissipated a much larger fraction of the mechanical work. Because the total dissipated energy as a function of shear strain is not orientation dependent, it is suggested that the orientation dependence of work-hardening must be related to the orientation dependence of energy storage. Our experimental results tend to disagree with the hypothesis that the production and subsequent annihilation of point defects is the dissipative mechanism. The results are, on the other hand, consistent with the hypothesis that the production and annihilation of dislocations is the dominant dissipative mechanism.