Plastic deformation of polycrystals of nickel at low temperatures

Abstract

1. The temperature dependence of yield stress of polycrystalline nickel over a wide range of low temperatures is represented by a segment (300–4.2°K) deriving from the thermal activation concept and a segment (T≤4.2°K) in which the yield stress depends weakly on temperature. This behavior, with consideration of the purity and polycrystalline character, is qualitatively similar to the behavior for other metals with face-centered cubic lattice. 2. Study of the strain-rate dependence of the strength parameters of nickel in the interval of 6.7·10−6 to 6.7·10−2 sec−1 has shown that, with drop of temperature below 135°K, the strain-rate dependence changes, a fact apparently due to an increasing role of dynamic effects in dislocation movement. 3. A dependence of yield stress of nickel on strength of a steady magnetic field has been noted, the yield stress increasing with increase in field strength, especially sharply at fields below the saturation value.