Precision measurements of critical resolved shear stress in CuMn alloys

Abstract

The critical resolved shear stress τ 0( T) and the activation volume V( T) of Cu Mn single crystals were measured in the temperature range from 4 to 450 K for 2.0 ⩽ c ⩽ 7.6 at.% Mn. For T ⪢ 20 K the temperature dependence of τ 0 and V can be described consistently by the concept of thermally activated dislocation motion. Below about 20 K the curvature of τ 0( T) changes sign and approximates a finite value for T → 0 K. These deviations from ordinary thermally activated glide behaviour are discussed in terms of inertial effects, sample heating and quantum effects like tunneling and zero-point vibrations of dislocation segments. A satisfactory explanation of the new anomaly is possible only by the theory of zero-point vibrations of dislocations.