SPRING-BACK CHARACTERISTICS OF GRAIN-REFINED MAGNESIUM ALLOY ZK60 SHEET

In this work, the effect of grain size on the spring-back characteristic was investigated by carrying out air-bending test using magnesium alloy ZK60 sheet with thickness of 0.5 mm at the various temperatures from room temperature to 300 °C. The angles of the bent specimen before and after unloading were measured in order to quantify spring-back amount. It was found out from the bending tests that when the specimens with grain sizes of 14.66 and 60.71 µm were bent by 90°, the amount of spring-back was relatively small at the testing temperature range and was in the range between -2.5° and 2.5°. On the other hand, the spring-back amount dramatically increased at room temperature and phenomenon of spring-go was observed at high temperature when the specimen with submicro grain size of 0.98 µm was bent by 90°. From this finding, it was confirmed that the different spring-back characteristics according to the grain size takes place and thus the grain size of material is one of the important factors which have an effect on the spring-back.