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

Abstract

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°C were investigated. The forming limit increased rapidly with temperature up to 200°C, and increased slightly thereafter. In the range from 200 to 300°C, the FLC0 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°C and above, negligible springback was observed over the range of BHF’s used. With increasing temperatures, springback decreased rapidly up to 200°C, and very slowly afterward. In nonisothermal tests, considerable springback was observed, even at temperatures of 200°C or higher; furthermore, it decreased almost linearly with increases in both the temperature and BHF.