An Investigation of Cavitation in the Tensile Testing of a Spray-Cast Aluminum Alloy Processed by ECAP

Abstract

A commercial aluminum 7034 alloy, produced by spray casting and having an initial grain size of ~2.1 μm, was subjected to equal-channel angular pressing (ECAP) through six passes at 473 K. In the as-pressed condition, the microstructure was reasonably homogeneous and the grain size was reduced to an ultrafine grain size of ~0.3 μm. This alloy contains MgZn2 and Al3Zr precipitates which restrict grain growth. In tensile testing at 673 K after processing by ECAP, an elongation of >1000% was achieved at a strain rate of 1.0 × 10-2 s-1 corresponding to high strain rate superplasticity. Quantitative cavity measurements were conducted on the specimens after tensile testing for both the as-received condition and after ECAP. These measurements reveal a significant number of small cavities in the samples and especially in the sample that exhibited a very high elongation. This paper describes the morphology of cavity development in the spray-cast aluminum alloy in both the as-received and as-pressed condition.