Plastic deformation of tantalum single crystals: II. The orientation dependence of yield

Abstract

The plastic deformation phenomena associated with the yielding of single crystals of tantalum are described as a function of orientation at 273 °K and 77 °K in tension and at 293 °K and 77 °K in compression. The orientation dependence of the yield stress in tension was found to be consistent with a critical resolved shear stress law for slip on a {110}〈111〉 system for the whole orientation range at 273 °K and part of the orientation range at 77 °K. The results are interpreted in terms of the Chen and Maddin model of composite slip on non-parallel {110} planes sharing the same slip direction. The anomalies in the orientation-dependence of the yield stress in tension at 77 °K are discussed in terms of the asymmetry of slip on {112} planes, and the reduced mobility of jogs in certain orientations. The orientation dependence of the yield stress in compression was not consistent with any critical resolved shear stress law.