Development and Analysis of Al7075 Alloy Materials Using Press and Sinter Processing

Al7075 alloy composition powders of ready to press Alumix 431/D and gas atomized pre-alloyed Al7075 were consolidated using press and sinter processing for structural application. Both powders exhibit similar overall compositions except for a small Sn content in Alumix 431/D and are very compressible using admixed and die wall lubricants. Green compacts were delubed and sintered in N₂ (g) for 60 min. at temperatures guided by thermal analysis of powders. Sintering results show that Alumix 431/D increases from green density to near theoretical density due to a low melting temperature transient liquid phase that forms at the majority of powder particle interfaces. Alternatively, pre-alloyed Al7075 does not increases in density during sintering from green density due to the formation of only a supersolidus transient liquid at the melting temperature of the powder. The supersolidus liquid phase that forms during sintering of Al7075 powder does so at a minority of powder particle interfaces thus not facilitating sintering density increase. These results indicate that development of Al7075 materials for net or near shape processing using press and sinter methods should technically work towards near theoretical density materials exhibiting homogeneous microstructures and compositions to maximize structural properties.