Investigation Of The Effects Of Alloying Elements On The Wettability Of Cu/W And Study Of The Wettability Between NdFeB And Sn-Zn-Bi Alloys

The wettability of liquid on solid and interfacial interaction is a common physical and chemical phenomenon in the material fabrication and processing. Besides the scientific significance, both of them are of importance for technological applications of materials, which decide the possibility of material fabrication and properties. Nowadays, there are no related reports in more detail about the effects of various factors on the wetting characteristics between Cu and W and between Sn-Zn-Bi alloys and NdFeB magnet. Based on the analysis mentioned above, the influence of temperature, contents of alloying elements and the compound addition of alloying elements on the wettability between copper alloys and W are studied respectively through using sessile drop method. Meanwhile, the effects of temperature, contents of alloying elements, atmosphere conditions as well as the intensity of electric field on the wetting characteristics of Sn-Zn-Bi alloys and NdFeB systems are also investigated. The purpose of this investigation is to optimize the infiltration technology and provides the gist of basic theory for the preparation of the composites with good combined properties.Firstly, the contact angles of Cu alloys with different alloying contents of Mn, Ni, Cr and Ti on W substrate in vacuum are measured respectively. The results show that the additions of Mn, Ni and Cr into Cu liquid reduce the contact angle between Cu and W and that the contact angle could be gradually decreased with the increment of Mn, Ni and Cr contents. The contact angles of copper alloys with the same additive contents of Mn element on W substrate decrease with increase of temperature. The interface is analyzed by EDS and EPMA. It reveals that the improvement of the wettability is related to the diffusion of elements between sessile drop and substrate, increasing temperature is helpful to enhance the interfacial diffusion and the extent of inter-dissolve. The mechanism may be considered as diffusion-solution wetting, i.e. thecombination of reactive wetting and non-reactive wetting, which decreases the interfacial tension.Secondly, the effects of the ratio of two elements of the simultaneous addition of Cr-Ni,Mn-Ni and Mn-Cr on the wettability between Cu alloys and W in vacuum are examined systematically. it is found that, for Cu/W system, the lower the ratio of Cr and Ni elements, the better the wetting characteristics; the liquid droplet of copper alloys on W substrate exhibits the best wettability when Mn:Ni = 1:4; but the effects of the ratio of Cr and Mn elements relate closely to that of the temperature, the wettability between copper alloys and W substrate is optimal at 1150℃.Thirdly, the wetting characteristics between pure Sn, Zn, Bi and NdFeB are investigated, and the effects of different atmosphere conditions,different temperatures, different additive contents and the different intensity of electric field on the wetting characteristics between Sn-Zn-Bi alloys and NdFeB magnet are also studied. For Sn-Zn-Bi alloys,the additions of Zn and Bi contribute to enhancing the wettability on NdFeB substrate. In vacuum and nitrogen, Zn always spreads on NdFeB substrate, but Sn does not scatter all the time. Sn-Zn-Bi alloy system shows good wettability in vacuum but does not melt down due to the surface oxidization in nitrogen. The wettability of pure Bi and Sn-8.5Zn-5Bi to NdFeB is improved significantly with increase of the temperature. With exerting electrical field and increase of electrical intensity, the interface energy decreases and facilitates the elements diffusion which leads to the decrease of the contact angle consequently, thus improves the wettability of low melting point elements/alloys on NdFeB. However, the mechanism of the effect of electric field on the wettability between metallic liquid and solid is still well worth further investigating.