Fabrication of bulk ultrafine-grained materials through intense plastic straining

Ultrafine grain sizes were introduced into samples of an Al-3 pet Mg solid solution alloy and a cast Al-Mg-Li-Zr alloy using the process of equal-channel angular (ECA) pressing. The Al-3 pet Mg alloy exhibited a grain size of similar to 0.23 mu m after pressing at room temperature to a strain of similar to 4, but there was significant grain growth when the pressed material was heated to temperatures above similar to 450 K. The Al-Mg-Li-Zr alloy exhibited a grain size of similar to 1.2 mu m, and the microstructure was heterogeneous after pressing to a strain of similar to 4 at 673 K and homogeneous after pressing to a strain of similar to 8 at 673 K with an additional strain of similar to 4 at 473 K. The heterogeneous material exhibited superplastic-like flow, but the homogeneous material exhibited high-strain-rate superplasticity with an elongation of >1000 pet at 623 K at a strain rate of 10(-2) s(-1). It is concluded that a homogeneous microstructure is required, and therefore a high pressing strain, in order to: attain high-strain-rate superplasticity (HSR SP) in ultrafine-grained materials.