Glass Forming, Crystallization And Mechanical Property Of CuZrAl And CuZrAlAg BMG

The glass forming ability, the behavior of crystallization and mechanical properties of the Cu-Zr-based bulk metallic glasses have been investigated. Cu55-xZr45Alx (x=4,5,6,7,8) and Cu49-xZr45Al6Agx (x=2,3,4,5,6) have been prepared with copper mold casting method. The optimized compositions were Cu49Zr45Al6 and Cu45Zr45Al6Ag4 by means of XRD and DSC. The reasons of the element of Ag added which has been enhanced the glass forming ability of the Cu49Zr45Al6 bulk metallic glasses has been analysised.The crystallization kinetics of Cu49Zr45Al6 and Cu45Zr45Al6Ag4 bulk metallic glasses was investigated by means of DSC under nonisothermal conditions. The activation energies for the crystallization was evaluated by Kissinger's equation. The results show that the crystallization process of Cu49Zr45Al6 and Cu45Zr45Al6Ag4 bulk metallic glasses can be regarded as a kinetically modified thermodynamic phase transformation process. The crystallization activate energy of Cu49Zr45Al6 was 371.3kJ/mol, which figured its high thermal stability.According to the isothermal annealing with different times in super-cooled liquid region, the isothermal crystallization process of Cu45Zr45Al6Ag4 was studied. The tetragonal phase of Al3Zr was the first precipitation phase. Finally, the annealed sample was composed of tetragonal Zr2Cu, cubic Al3Zr, orthogonal Cu8Zr3 and Cu10Zr7. Based on the function of crystallized volume fraction and the annealing time, the JMA curve of Cu45Zr45Al6Ag4 at 730 K was established.The compression properties and the micro-hardness in room temperature have been studied in this research. The plasticity of Cu45Zr45Al6Ag4 reached to 3.6%, which was higher than that of Cu49Zr45Al6. The micro-hardness of Cu45Zr45Al6Ag4 (635Kg/mm2) was higher than Cu49Zr45Al6.