Wetting Behaviors Of Several Ni-and Fe-base Alloys By Molten Sn(Bi) And Their Comparison

Amorphous alloys, which are considered to be the potential engineering materials,possess a series of superior physical and chemical properties. However, the amorphousalloys are in the metastable state, and tend to transform to stable state during heat input. Thetransformations include structural relaxation, crystallization and so on, leading to the changeof energy and structural of materials. Therefore, the control of heat input is one of the mostimportant things during the connection of metal and amorphous. Soldering, as alow-temperature joining process, can effectively avoid structural transformation ofamorphous alloys during welding and can provide technical support for the connection ofamorphous alloys.In this thesis, we mainy investigated the wettability and interfacial microstructures ofmolten Sn(Bi) on the metastable BNi–2, BNi–5, Ni80P20, Ni66.8Cr6.2Cu6.5P20.5substrates andFe–42Ni alloys annealed at different temperatures using a dispensed sessible method. Wefurther done a comparative analysis of the Sn/Fe–42Ni system and the Sn/Fe40Ni38Mo4B18system. The major results of the present study are as follows：(1) The wettability of molten Sn(Bi) on the metal or amorphous substrates were closelyrelated to the experimental environment. In vacuum, the oxide film covering the substratesurfaces would deteriorate the wettability, leading to a large contact angle. Thehigh-temperature preannealing treatment favor to improve the wettability. In Ar–10%H2, theFe oxides and Ni oxide on the substrate surface could be reduced efficiently by H2, whichcan improve the wettability of system.(2) For metal/metal system, the thickness of product layer is much thicker in Ar–10%H2compared with that in vacuum. In Ar–10%H2, a fine uniform intermetallic (IMC) layerformed in the early wetting stage, to a large extent, impedes the further growth of the IMCphases. However, in vacuum, the IMC phase nucleates preferentially in the regions wherethe oxide film is much thinner and the inhomogeneous atomic diffusion at different regions leads to a much thicker reaction product layer.(3) The high active surface atoms of amorphous and the energies come from thestructure change due to diffusion of components or chemical reaction at the interface providethe driving forces for the spreading of molten to some extent. So the wettability ofFe40Ni38Mo4B18amorphous by molten Sn is superior to the system of Sn/Fe–42Ni.(4) The primary crystallization at the initial state has little effect on the wettability ofsystem. While the primary crystallization induced by annealing would deteriorate thewettability of system.