Effect of ECAP Strain on Deformation Behavior at Low Temperature Superplastic Regime of Ultrafine Grained 5083 Al Alloy Fabricated by ECAP

A series of tensile testing was carried out on the ultrafine grained 5083 Al alloy, which was fabricated by equal channel angular pressing (ECAP) with different ECAP strains, at low temperature superplastic (LTS) temperature of 548K. This investigation was aimed at examining the effect of the ECAP strain inducing different microstructure in the alloy on the deformation mechanisms at LTS regime. The most distinguishable microstructural evolution by increasing the ECAP strain from 4 to 8 was an increment of a portion of high angle boundaries while the (sub)grain size remained almost unchanged. The sample after 4 passes (a strain of 4) did not exhibit LTS, but superplastic elongations were obtained in the sample after 8 passes (a strain of 8). An analysis of the mechanical data in light of the standard deformation mechanisms revealed that deformation of the sample after 4 passes was governed by dislocation climb while grain boundary sliding attributed to LTS of the sample after 8 passes. The difference of the deformation mechanisms in the present case was discussed in terms of the microstructures developed under different ECAP strains.