材料期刊网

The glass-forming ability of two alloys, Zr(64.9)Al(7.9)Ni(10.7)Cu(16.5) and Zr(47)Cu(37.5)Ag(7.5)Al(8), prepared by arc-melting a mixture of Zr, Cu, Al, Ni and Ag elements is studied as a function of casting temperature. Other processing parameters such as the alloy melt mass, and the vacuum and injection pressures during the copper-mold-casting process are kept constant so just the influence of the casting temperature is considered. The casting temperature determines the characteristics of the liquid melt and the cooling rate. The glass-forming ability is discussed in terms of dissipation of pre-exiting, metastable local-ordering clusters that act as nucleation sites promoting crystallization, the cooling rate at high casting temperatures, and the presence of oxygen in the alloys, which is increased at high casting temperatures. It is found that the glass-forming ranges of alloys shrink as the glass-forming size approaches a critical value. The optimum temperatures are around 1450K and 1550K for Zr(64.9)Al(7.9)Ni(10.7)Cu(16.5) and Zr(47)Cu(37.5)Ag(7.5)Al(8) alloys respectively. The alloys were studied by XRD, TEM, oxygen-level determination, and DSC.