STRENGTH ANISOTROPY IN A COLD-COMPACTED LOW ALLOY STEEL POWDER

摘要

Currently used models for cold compaction of ductile powders consider strength as a function of density alone. However, a number of studies have shown that strength is dependent on other variables besides density, including the stress path used for consolidation. Fleck's model (1995) offers the first approach to understanding the origin of this path dependence and identifies the orientational anisotropy of deformation at interparticle contacts as the origin of this behavior in ductile powders. Assuming this assertion is correct, in addition to path dependence, powder compacts produced by non-isostatic stress paths also should exhibit anisotropic strength. Evidence documenting strength anisotropy in a closed die cold-compacted low alloy steel powder (Distaloy AE) will be presented. Evidence is provided primarily from tensile strength testing and SEM fracture surface analysis. Data concerning post-sintering strength anisotropy will also be presented.