Doubling the critical size for bulk metallic glass formation in the Mg-Cu-Y ternary system

Mg-Cu-Y alloys with optimal glass forming ability have been found at off-eutectic compositions. The critical size for bulk metallic glass formation at the pinpointed compositions more than doubles that of the previously discovered eutectic Mg₆₅Cu₂₅ Y₁₀ alloy, leading to fully glassy rods with near-centimeter diameters in the ternary system upon copper mold casting. The result is a striking demonstration of the strong composition dependence of the glass forming ability, as well as of the need to scrutinize off-eutectic compositions. The implications of the discovery are discussed.