Experimental Determination of Forming Limit Diagram and Springback Characteristics of AZ31B Mg Alloy Sheets at Elevated Temperatures

摘要

A warm/hot formability testing apparatus was designed and fabricated for this study. The forming limit curve (FLC) and springback characteristics of AZ31B Mg alloy sheets at elevated temperatures of up to 300 deg C were investigated. The forming limit increased rapidly with temperature up to 200 deg C, and increased slightly thereafter. In the range from 200 to 300 deg C, the FLC_0 was found to be six to seven times higher than at room temperature. In isothermal springback tests, the effect of the blank holding force (BHF) on springback differed slightly from that for other metal sheets at low temperatures. At 200 deg C and above, negligible springback was observed over the range of BHF's used. With increasing temperatures, springback decreased rapidly up to 200 deg C, and very slowly afterward. In nonisothermal tests, considerable springback was observed, even at temperatures of 200 deg C or higher; furthermore, it decreased almost linearly with increases in both the temperature and BHF.