Effect of elements with positive enthalpy of mixing on mechanical properties of bulk metallic glasses

Samples of (Cu46Zr46Al8)100−xZx metallic glass forming alloys with diameters 2-6 mm were prepared by injection casting. The effect of minor amounts of elements Z = Gd, Co and Re with positive enthalpy of mixing within the Gd-Zr, Cu-Co and Cu-Re terminal systems was compared. The addition of Gd up to x = 2 slightly enhances the glass forming ability, Co reduces the critical diameter of bulk metallic glass formation, whereas even for small fractions of Re bulk samples were crystalline, but only amorphous splats can be prepared. Both Gd and Co diminish the crystallization temperature Tx with respect to the Cu46Zr46Al8 master alloy, but in Re-bearing splats Tx is increased. Alloying with optimum amounts of Gd and Co up to x = 2 leads to plastic deformability of rods, 2 and 3 mm in diameter, in comparison with the brittle Cu46Zr46Al8 bulk metallic glass.