Deformation and Recovery of Iron Polycrystals

Abstract

<p>The effect of grain size on the work hardening behavior of polycrystalline iron, copper, and 70/30 alpha brass has been studied using stress relaxation techniques. The stress relaxation technique has been used to monitor the variation of internal stress during work hardening as a function of grain size in these materials. It is shown that, for certain conditions dependent on the temperature and the nature of slip, the work hardening behavior of a metal polycrystal is grain size dependent and can be expressed in terms of a modified Hall- Fetch equation with a slope dependent on the degree of plastic strain. A simple dimensional argument is developed to show that under conditions of planar slip, where the slip distance is equivalent to the grain diameter, the grain size dependent work hardening is related to the accumulation of geometrically necessary dislocations required for the compatible deformation of the polycrystal.</p> <p>Recovery experiments have been used to study the thermal stability of the work hardened structure formed at different deformation temperatures in iron polycrystals.</p>