Thermoplastic gas pressure forming of bulk metallic glass sheets under biaxial tension

The deformation behaviour and structural evolution of bulk metallic glass sheets were studied under biaxial tension in supercooled liquid state. The sheets were gas pressure formed into hemispherical and semi-ellipsoid domes using dies with aspect ratios of 1:1 and 3:2, respectively, at the optimum temperature of 676 K. The structural evolution of the metallic glass sheets was examined after deformation. The stress distributions of the bulging sheets are calculated employing a finite element model. It was found that the stress state of biaxial tension accelerates nanocrystallization, which leads to an increase in the hardness of metallic glass. The gas pressure applied, bulging time, and temperature are the principal factors involved in the formation of products.