Casting effect on softening of metallic glasses

Cooling rate-induced softening in Y-based metallic glasses were verified in this work. By varying the speed of the roller in the melt-spinning process, it is found the hardness of the ribbon decrease with the cooling rate. Nanoindentation test also indicated that the ribbon at a higher cooling rate shows higher deformation energy. Contrary to crystalline materials, whose hardness usually increases with the cooling rate, the softening of metallic glasses is attributed to high concentration of defects frozen by fast cooling, and thus more structural relaxation during deformation.