AgCuZnSn钎料的热力学特性

Thermodynamics characteristics of AgCuZnSn brazing filler metals

为了揭示AgCuZnSn钎料的热力学特性,以BAg50Cu Zn钎料为原材料,采用熔炼合金化方法制备高锡AgCuZnSn钎料。借助差示扫描量热仪(DSC)测定不同Sn含量AgCuZnSn钎料的熔化温度,运用热分析动力学中的非等温微分法和积分法分析AgCuZnSn钎料的相变热力学特性。利用热力学熵的概念,提出AgCuZnSn钎料钎焊工艺熵和接头性能熵的数学表达式。结果表明:随着Sn含量升高,AgCuZnSn钎料的吸热峰向左偏移,且在吸热峰钎料相变温度区间变窄。非等温微分法和积分法得到的AgCuZnSn钎料的相变活化能随着Sn含量增加逐渐增大;当Sn含量相同时,两种方法得到的钎料相变活化能几乎相同。当Sn含量为7.2%(质量分数)时,AgCuZnSn钎料的相变活化能和指前因子值最大,分别为364.46 k J/mol和7.29×1020。试验结果证实了钎焊工艺熵和接头性能熵的表达式在一定程度上可定量表征AgCuZnSn钎料的钎焊性能。

By revealing the thermodynamic properties of AgCuZnSn brazing alloys, brazing alloys of high Sn content were prepared using melting alloyed method based on BAg50CuZn substrate. The melting temperature of brazing alloys was observed by differential scanning calorimeter （DSC）, and its phase transformation thermodynamic characteristic was analyzed with the thermal analysis kinetics of non-isothermal differential and integral methods. The mathematical expression of process entropy and performance entropy of brazing alloys were proposed. The results show that the DSC endothermic peak of AgCuZnSn brazing alloys shifts to the left, and its phase transformation temperature interval would be narrower with the increase of Sn content. The phase transition activation energy of AgCuZnSn brazing alloys gradually increases using non-isothermal methods. Under the same Sn content, the phase transition activation energy of brazing alloys with non-isothermal differential method is exactly the same as that of integral method. When Sn content is 7.2% （mass fraction）, the transition activation energy and pre-exponential factor of brazing alloys reach the maximum, which are 364.46 kJ/mol and 7.29×1020, respectively. The results indicate that the expression of process entropy and performance entropy could quantitative analyze the brazability of AgCuZnSn brazing alloys.