Distortion in a sintered 7000 series aluminum alloy

Abstract

The 7000 series aluminum alloys processed using elemental powder mixtures are prone to distortion, which is manifest as hourglassing or waisting in cylindrical specimens. By characterizing the density distribution using hardness measurements, it is shown that the green density is not evenly distributed through a part, even though aluminum is relatively soft and readily compacted. Because the density equilibrates during sintering, the non-uniform green density leads to distortion. The cause of this distortion is a result of differential shrinkage, which occurs during sintering as well as on solidification during cooling from sintering. Distortion can be controlled by increasing the compaction..