Enhanced glass forming ability in Zr-based bulk metallic glasses with Hf Addition

We report on the partial substitution of Hf for Zr in Zr57Nb5Cu15.4Ni12.6Al10 bulk metallic glass (BMG) and the resulting enhanced glass forming ability and processability. Critical casting thickness increased from less than 14 mm for Zr57Nb5Cu15.4Ni12.6Al10 to more than 16 mm for Zr45Hf12Nb5Cu15.4Ni12.6Al10. This improvement contrasts with earlier reports of reduced glass forming ability with partial substitution of Hf for Zr. Furthermore, the new BMG alloy exhibited one of the best bend ductility reported to date for BMG samples that are more than 4 mm thick. The improved glass forming ability with Hf substitution is presented and the underlying factors for improved glass forming ability are discussed.