Direct as against indirect dispersion work hardening

Abstract

Abstract In a polycrystal consisting of a matrix and a uniform dispersion of particles or bubbles with a grain size determined by critical Zener pinning it is known that the yield stress is controlled not so much by direct particle—dislocation interactions as by indirect particle-grain-boundary-dislocation interactions. After yield, dislocations accumulate in the matrix, at hard particles (but not at bubbles) and at grain boundaries. These accumulations cause work hardening. In the case of hard particles the particle (direct) work hardening and the grain-boundary (indirect) work hardening are equal. In the case of bubbles the direct work hardening is approximately zero. At low strains, therefore, indirect hardening dominates the flow stress. Only at high strains is the matrix work hardening significant and in strong alloys, with a high volume fraction of small particles, it is never significant