Grain refinement of AZ31 magnesium alloy sheets fabricated by rolled and heat treated twin roll cast plate

For the purpose of the development of a cheap, excellent in formability AZ31 alloy sheet, the influence of rolling and heat-treatment on grain refinement was examined using the cast strip processed by the twin-roll casting as a sample. As a result, it became clear that the almost uniform, fine grain structure of average grain size 4.7 μm is obtained by performing appropriate rolling, the intermediate and final annealing for 1 h at 300°C, respectively, after homogenization for 8 h at 450°C. In addition, finest average grain size of 3.2 μm was obtained by the model experiment to imitate flash annealing. 0.2% proof stress increased with decreasing in the grain size, and the relation of Hall-Petch was almost approved between them.