High copper content bulk glass formation in bimetallic Cu-Hf system

We report in this article that strip-shaped amorphous samples with thicknesses from 0.5 to 2 nun were successfully synthesized for binary Cu-Hf alloys containing 60 to 68 at. pct Cu by the traditional copper mold casting method. The best glass former Cu66Hf34 with casting thickness up to 2 turn has an undercooled liquid region (DeltaT = T-x - T-g, where T-g is the glass transition temperature and T-x is the onset temperature of the first crystallization event) of 51 K, which is somewhat narrow compared with other neighboring 2 alloys in the same system. The bulk glassy Cu66Hf34 alloy exhibits Vicker's Hardness (H-v) similar to 779 kg/mm(2), Young's modulus similar to108 GPa, fracture strength similar to2.1 GPa, and an almost constant elastic elongation similar to1.8 pct upon compression. The discovery of Cu66Hf34 as a bulk glass confirms the existence of rather simple bulk-glass-forming metallic systems. Moreover, the present Cu-Hf alloys may be the highest copper content bulk metallic glasses reported to date, to the best of our knowledge.