Enhancing stretch formability of an AZ31 magnesium alloy sheet via differential heating of the punch and die

The formability of AZ31 magnesium alloy sheets was assessed by biaxial stretching using the novel method of differential heating and compared to conventional isothermal heating. The isothermal limiting dome height (LDH), measured by the Erichson test, showed a notable increase from 13.5 mm at ambient temperature to 27.7 mm at 300 °C. On the other hand, a reduction in the punch temperature, facilitated by differential heating between the punch and the die was found to enhance LDH to 37.4 mm under an optimal condition that was achieved with a die temperature of 300 °C and a punch temperature of 150 °C. Similar to LDH, the limit strain in the plane-strain condition (FLD 0 ) increased from 0.4 in the isothermal heating to 0.54 in the differential heating, and the overall level of forming limit diagrams (FLDs) also showed significant improvements in the differential heating regime. The observed enhanced formability was found to be attributable to the suppression of cavity formation when the punch is colder than the die. It is therefore concluded that the application of the differential heating technique suggests significant potential for improved processability in magnesium alloy sheets under these conditions.