Application of High-Pressure Sliding for Grain Refinement of Al and Mg Alloys

An earlier study showed that high-pressure sliding (HPS) is effective for grain refinement of pure Al in a rectangular sheet form using the principle of high-pressure torsion. In this study, the HPS is applied for grain refinement of an Al-3%Mg-0.2%Sc alloy and an AZ61 Mg alloy. HPS was conducted under a pressure of 1 GPa with sliding distances of 10 to 30 mm at room temperature for the Al alloy and at 473 K for the Mg alloy The average grain size is ~300 nm for both the Al and Mg alloys, respectively. Tensile tests showed that a superplastic elongation of ~1500% is achieved in the Al-3%Mg-0.2%Sc alloy at 573 K with an initial strain rate of 3.3x10-3 s-1 and of ~600% in the AZ61 alloy at 573 K with an initial strain rate of 1x10-3 s-1.