Warm Pressing of Al Powders: An Alternative Consolidation Approach

This paper presents the warm pressing as an alternative powder metallurgy approach to conventional press-and-sinter or hot working (e.g., extrusion, forging) consolidations of Al powders into complex near-net-shape parts with required mechanical properties. In this study gas-atomized Al powders (A1050 and A6061) with various particle sizes were consolidated by uniaxial pressing, with minimum plastic deformation induced, at temperatures of 22 and 430 °C, respectively. The materials pressed at 22 °C showed poor strengths, ductility and electrical conductivity. The properties were improved markedly when pressing temperature increased to 430 °C and reached values comparable to A1050 and A6061 materials fabricated by conventional powder and ingot metallurgy approach. Similarly, the properties of the materials pressed at 22 °C were improved after annealing at 300 °C for 2 h. This indicated the formation of sufficiently strong interfacial bonding between native oxide layers on adjacent Al powder particles (i.e., grains) when processing temperature increased to 300 °C. With interfacial bonding established, the fracture mechanism changed from brittle to ductile character.