Microstructures of Powder and Conventionally Processed 7075 Aluminum Alloy

Aluminum alloy powder of the 7075 composition was consolidated by warm upset and extrusion. Commercial cast and wrought materials was also extruded to serve as a control. Results of varying the length of time at solution treatment temperature indicate that the powder materials is far less resistant to recrystallization than the conventional material. Optical and transmission electron microscopy revealed that after identical post-extrusion solution treatments the substructure formed during extrusion throughout the commercial material was stable while the powder material retained substructure only near the edges of the rectangular extrusion and had undergone complete recrystallization toward the center. These results are explained in terms of the presence of a certain particulate constituent and the amount of warm working, both of which appear to influence substructure formation and stability. The presence or absence of the observed subgrain structure was shown to influence tensile properties either directly or through its effect on aging response. The results obtained by varying quench rates and employing cold work after solution treatment are compared for the powder and the conventional material and shed light on the various effects of chromium in the 7075 alloy.