Grain refinement of magnesium alloy sheets by ARB using high-speed rolling mill

Abstract

Applications of ARB to magnesium alloys were limited due to low deformability. The authors recently found that the rollability of the alloys is significantly improved in highspeed rolling. It is supposed that the severe plastic deformation of magnesium alloy sheets is feasible if rolling in ARB processes is conducted at high speed. In this study, AZ31B and ZK60A sheets are processed by ARB up to five cycles at 423K with a speed of 1000m/min. Vickers hardness increases with increasing number of ARB cycles, while the tensile strength shows the maximum after the second cycle. The grain size is reduced significantly at the first cycle and decreases gradually from the second cycle. The mean grain sizes after five cycles are 1.6μm for AZ31B and 1.8μm for ZK60A. It is concluded that ARB using high-speed rolling is effective for grain refinement of magnesium alloys.