Superplastic forming of Zr based metallic glass ribbons under equibiaxial tension

In this paper, the superplastic forming behaviour of a Zr based metallic glass ribbon at different die diameters is examined. The wall thickness distribution and the relative bulging height values of the ribbon are experimentally determined, and the results are in reasonably good agreement with the finite element method (FEM) findings. The ribbon demonstrated early failure in both tensile tests and gas pressure forming. It is considered that the presence of air pockets in the as cast ribbon is one of the reasons for this. The FEM results also demonstrate that the air pockets may develop into localised regions which may eventually lead to failure of the ribbon. The differential scanning calorimeter curves of the as cast and deformed specimens show that the onset temperature of crystallisation is changed after deformation. This change is related to its change of microstructure. More work is needed to improve the formability of the ribbon and to study the post-deformed properties of the metallic glass.