Abstract:A bulk amorphous Cu₄₆Zr₄₂Al₇Gd₅ alloy with a diameter of 3 mm was prepared by copper mould sucking cast. The effect of copper billet purity on the glass forming ability, thermal stability and microhardness of the alloy was studied. The bulk amorphous Cu₄₆Zr₄₂Al₇Gd₅ alloy with a diameter of 3 mm can be prepared using copper billet with lower purity to replace copper billet with higher purity in the proportion of 25% and 50%, while the alloy shows the characteristic of crystalline in the proportion of 75% or above. When the copper billet with higher purity is replaced with lower purity billet in the proportion of 25%, the glass transition temperature is about 669 K, the crystallization temperature is about 749 K and the supercooled region is about 80 K. When the copper billet with higher purity is replaced with lower purity billet in the proportion of 50%, the glass transition temperature is 684 K, crystallization temperature is 751 K and supercooled region is 67 K. The alloys all keep amorphous structure after heat treatment at 573 K for 1 h. The alloys in 25% proportion crystallize after heat treatment at 673 and 773 K for 1 h, which consist of substrate and second fine phase and have higher microhardness. The alloys in 50% proportion also consist of substrate and second fine phase, and have higher microhardness after heat treatment at 673 K for 1 h. There are two kinds of microstructures after heat treatment at 773 K for 1 h, white area consists of substrate and second fine phase, and grey area consists of white phase and grey phase. The microhardness increases sharply.

Key words: Cu₄₆Zr₄₂Al₇Gd₅ alloy; bulk amorphous alloy; crystallize heat treatment; microstructure; microhardness; purity effect