Microstructure and Superplastic Properties at Room Temperature in Zn-22Al Alloy after Equal-Channel-Angular Extrusion

摘要

Recently, it has been reported that high strain rate and/or low temperature superplasticity requires a very fine grain size, typically below 1 μm. In order to obtain ultrafine-grained and suitably homogeneous microstructures, in the present work, Equal-channel-angular extrusion (ECAE) has been conducted on Zn-22Al alloy under three conditions. Route 1 is extrusion at room temperature during spinodal decomposition, Route 2 is extrusion at room temperature after spinodal decomposition and Route 3 is extrusion at 373K after spinodal decomposition. Microstructure observations showed that ECAE samples pressed under each condition had an equiaxed grain size about 0.35 μm, 0.3 μm, 0.6 μm, respectively. As for the results of tensile testing at room temperature, the sample pressed at room temperature during spinodal decomposition exhibited the strain rate sensitivity exponent of 0.25～0.3 and a high elongation over 200 % below an initial strain rate of 10~(-2)s~(-1). Therefore, it is considered that deformation behavior like superplasticity may be attained. Conclusively, the deformation properties at room temperature in the present study were compared with the previous results.