The influence of temperature on the development of long-range internal stress during the plastic deformation of high-purity iron

Abstract

Strain-rate cycling tests have been performed during the tensile deformation of single crystal and polycrystalline specimens of two zone-refined irons in the temperature range 78–300°K. The application of the Johnston-Gilman velocity-stress relationship to the results permits an evaluation of the average effective stress and the average internal stress developed during the deformation. As the temperature of deformation was decreased the strain dependence of the effective stress changed from a decreasing function of strain to an increasing one. The internal stress resulting from deformation decreased with decreasing temperature and below about 175°K there was not sufficient internal stress developed to account for the observed hardening. The results suggest that at low temperatures the cutting of dislocations becomes an important hardening mechanism.