Nb添加对Cu-Zr非晶合金等温晶化动力学的影响

采用铜模吸铸法制备了Cu50.3Zr49.7Nbx(x=0,2)块体非晶合金.利用示差扫描量热分析(DSC)研究了2at％Nb的添加对Cu-Zr非晶合金在过冷液相区等温晶化行为的影响.结果显示Cu基合金的等温晶化动力学符合JMA方程的定量描述.含微量Nb的合金具有更长的晶化孕育时间、更宽的反应放热峰以及更低晶化速率常数k和Avrami指数n,与此同时局域Avrami指数n随晶化体积分数的变化和Nb的添加而改变.这表明微量Nb添加在抑制合金形核,提高其热稳定性的同时,也改变了Cu基合金的等温晶化过程.

Effect of Nb Addition on Isothermal Crystallization Kinetics of Cu-Zr Bulk Amorphous Alloys

Cu50.3Zr49.7-xNbx(x=0, 2) bulk amorphous alloys were prepared by copper mould suction casting. The effect of 2at% Nb addition on isothermal crystallization behavior of the Cu-Zr alloy in supercooled liquid region has been investigated by differential scanning calorimetry (DSC). Results show that the kinetics of isothermal crystallization of Cu based alloys can be well described by the Johnson-Mehl-Avrami (JMA) model. The minor-Nb-containing alloy exhibits longer incubation time for isothermal crystallization and broader reaction exothermic peak as well as lower crystallization rate constant k and Avrami parameter n. Meanwhile, the variation of local Avrami parameter n with crystallized fraction in the Nb-containing alloy is different from that of Nb-free one. This indicates that the Nb addition enhances the thermal stability against crystallization and changes the isothermal crystallization process of the Cu-based alloy.