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

Abstract:

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 oC, and the contact angle between the molten Sn-8.5Zn-7Bi alloy and NdFeB magnet is 53.2°.

Key words:sessile drop technique; wetting behavior; NdFeB magnet; Sn-Zn-Bi alloy system