Bulk metallic glass formation in binary Cu-rich alloy series – Cu100−xZrx (x=34, 36, 38.2, 40 at.%) and mechanical properties of bulk Cu64Zr36 glass

The compositional dependence of a glass-forming ability (GFA) was systematically studied in a binary alloy series Cu100−xZrx (x=34, 36, 38.2, 40 at.%) by the copper mold casting method. Our results show the critical casting thickness jumps from below 0.5 mm to above 2 mm when x changes from 34 to 36 while further increase in x reduces the critical casting thickness. The best glass former Cu64Zr36 does not correspond to either the largest undercooled liquid region (ΔT=Tx1−Tg, where Tg is the glass transition temperature, and Tx1 is the onset temperature of the first crystallization event upon heating) or the highest reduced glass transition temperature (Trg=Tg/Tl, where Tl is the liquidus temperature). Properties of bulk amorphous Cu64Zr36 were measured, yielding a Tg ~ 787 K, Trg ~ 0.64, ΔT ~ 46 K, Hv (Vicker's Hardness) ~ 742 kg/mm^2, Young's Modulus ~ 92.3 GPa, compressive fracture strength ~ 2 GPa and compressive strain before failure ~ 2.2%.