Study On Rolling Process, Microstructure And Mechanical Properties Of AZ31 Wrought Magnesium Alloy Sheet

In this paper, the rolling process and hot process technology of AZ31 wrought magnesium alloy sheet were discussed. The microstructure and the mechanical properties affected by the two processes were studied. The fracture mechanism and how to improve the plastic deformability effectively of AZ31 wrought magnesium alloy were discussed. Points of the study were as followed:①The correlation between the rolling process and the plastic deformability of AZ31 wrought magnesium alloy sheet;②The refine-grain technology of AZ31 wrought magnesium alloy sheet and the effect of annealing process on microstructure, mechanical and deep-drawing properties;③The correlation between the cold rolling plastic deformability and the fine-grain level of AZ31 wrought magnesium alloy sheet;④The plastic deformability and the fracture mechanism of refine-grain AZ31 wrought magnesium alloy.The results showed that:(1) The limit of pass processing rate during hot rolling could reach 59.23% which made two times than that of at low temperature with reasonable hot rolling process.(2) The microstructure and mechanical properties of hot rolled AZ31 wrought magnesium alloy sheet were tied up with annealing temperatures. The grain size of AZ31 wrought magnesium alloy grew large at first then reduced with increasing annealing temperatures, while, the deep-drawing property went in the opposite tendency. There was the best relationship between strength and tenacity at the annealing temperature of 350℃. The tensile strength and yield strength were 231MPa and 139MPa respectively, and the elongation was 14.9%.(3) The refine-grain technology of AZ31 wrought magnesium alloy was obtained, and the grain size could reduce from 12.2μm to 5.40μm.(4) The cold rolling capability of AZ31 wrought magnesium alloy had made a great improvement, after refining, and it made almost twice times the limit of pass processing rate than that of alloy without grain refinement. The total processing rate during cold rolling of that alloy reduced with the rose of pass processing rate, and the deformation of that sheet during cold processing became worse(5) The main fracture mode of AZ31 magnesium alloy turned from brittle failure before grain refining to ductile rupture after grain refining from SEM images analysis of the fracture surface of AZ31 wrought magnesium alloy sheet. The fracture mode of cold rolled fine grain AZ31 magnesium alloy sheet was different depended on the different annealing temperatures. Mostly, there was mischcrystal failure by observing the metallograph of tensile fractured alloy.(6) The plastic deformability of AZ31 wrought magnesium alloy had made a great improvement at room temperature under optimized cold rolling process.