Effect of a thermal annealing on the mechanical behaviour of green pm compacts

Abstract

Cold die compaction can produce different effects on the dimensional and mechanical behaviour of green PM compacts. They can be due to different causes, such as residual stresses, microcracks and others. Residual stresses should be relieved by means of applying thermal annealing treatments. In this work, the authors present the results obtained from uniaxial compression tests applied on green specimens of an atomised iron based powder, compacted to different densities and having undergone thermal annealings at several temperatures, always below the sintering one. The stress-strain compression curves obtained are compared with those corresponding to as compacted samples. The results seem indicate the existence of residual stresses that could act at different levels: microscopically, in the contact among particles, and macroscopically, in the overall specimen resistance.