High-pressure sliding using rod samples for grain refinement

Abstract

High-pressure sliding (HPS) is a process of severe plastic deformation (SPD) for significant grain refinement and it is similar to high-pressure torsion (HPT) as both processes are operated under high pressure. Whereas the HPT process uses disk or ring samples, the HPS process is applicable to rectangular sheet samples. In this study, it is demonstrated that the HPS process is also applicable to rod samples. To achieve a homogeneous microstructure throughout the cross section of the rod, the sample is rotated along the longitudinal axis after each processing. The HPS process is carried out on pure Al, Al alloys (Al-3%Mg-0.2%Sc, A2024 and A7075) and a Mg alloy (AZ61) under a pressure in the range of 1-2 GPa. It is shown that a homogeneous microstructure is developed in all samples through rotation along the longitudinal axis by 60 degrees after each processing. The Al alloys and the Mg alloy exhibit grain sizes well less than 500 nm and superplastic elongation well more than 400% for the A2024 and A7075 alloys and well more than 1000% for the Al-3%Mg-0.2%Sc alloy and the AZ61 alloy. It is thus antgicipated that the HPS process provides good potential for scaling-up the sample size through not only sheets but also rods.