Effect of upper-die temperature on the formability of AZ31B magnesium alloy sheet in stamping

To ensure the temperature and formability of magnesium sheet metal transferring from a continuous oven, stamping of magnesium alloy sheet normally requires a setting of stationary heating oven in which lower-punch and binder are heated simultaneously. This paper studied the effect of unheated or extra heated upper-die with different temperatures on AZ31B magnesium sheet metal's formability in stamping. Forming limit curves (FLC) under different temperature upper-die were generated to analyze the temperature effect, which shows that the formability decrease significantly as upper-die temperature drops. Moreover, temperature fields simulated through thermo-mechanical coupling FEM simulation and microstructure of different specimen region indicate inhomogeneous mechanical properties due to temperature gradient, which results in different modes of crack initiation and propagation. Finally, FLC result was verified through a tryout stamping of automobile hinge cover.