Sn-8.5Zn-xBi合金系与NdFeB磁体间的润湿性

Wettability of Sn-8.5Zn-xBi Alloy System with NdFeB Substrate

采用座滴法分别研究在真空和氮气气氛中和不同温度条件下纯金属Sn,Zn,Bi及Sn-Zn-Bi系合金在NdFeB磁体上的润湿性。结果表明:单一元素Sn和Bi与NdFeB磁体间的润湿性不好,接触角比较大;而Zn与NdFeB磁体间的接触角为零,润湿性非常好。为了获得熔点较低、又与NdFeB磁体间润湿良好的合金,配制一定成分的Zn-Sn-Bi系合金,并测定其熔点。Zn-Sn-Bi合金中,当Bi含量增加到1.0%(质量分数,下同)以后,随着Bi含量的增加,Sn-Zn-Bi合金与NdFeB磁体间的润湿性改善,原因是Bi减小了液态合金的表面张力,计算和实验都证实了这一点。Sn-8.5Zn-7Bi熔点为194.3℃,合金与NdFeB磁体间的接触角仅为53.2°。

Wetting behaviors of NdFeB magnet by molten Sn-Zn-Bi alloy systems at different temperatures were investigated by the sessile drop technique under vacuum and N2 atmosphere. The results show that the wettabilities of NdFeB magnet with liquid pure Sn or pure Bi elements are poor, and their contact angles are higher. While the wettability of NdFeB magnet with liquid pure Zn element is perfect, and the contact angle is near zero. The Sn-Zn-Bi alloys with certain composition were prepared and their melting points were measured in order to obtain good wettability of NdFeB magnet with molten Sn-Zn-Bi alloy and lower melting point. The wetting angles between Sn-Zn-Bi alloys and NdFeB magnet decrease dramatically with increasing the Bi contents from 1.0% to 7.0% （mass fraction） because the surface tension of the alloys is decreased by the addition of Bi, which were confirmed by calculation and experimental results. The melting point of Sn-8.5Zn-7Bi alloy is 194.3 ℃, and the contact angle between the molten Sn-8.5Zn-7Bi alloy and NdFeB magnet is 53.2°.