Structure and properties of rapidly solidified foils of triple Bi – In – Sn alloy and solder joint based on it

The alloy Bi32In41Sn27 was produced by fusing the components in quarts ampoules. A piece of alloy of 0.2 g was heated and injected onto the inner polished surface of rapidly rotating copper cylinder with a diameter 20 cm. The alloy was solidified in the form of a foil up10 cm long and up to10 mm wide. Foils with a thickness of 30 – 100 micrometers were used for the study. The chemical compositions of the foil in the layers in contact with surface of the mold and the atmosphere are coincided within the measurement error. A rapidly solidified alloy Bi32In41Sn27 consists of ε-phase (BiIn) and γ-phase (Sn4In) having a dispersed structure. The average value of the chords dγ of random secants located on the sections of γ-phase and average value of the specific surface area of the interphase boundary Sε – γ, formed by ε- and γ-phases, depend on the expose time t at room temperature; their properties are described by equations d = 0,58 + 0,29lnt and Sε – γ = 2,9 − 0,43lnt, correspondly. The alloy foils have a microcrystalline structure and well-defined texture (0001) of the γ-phase and poorly expressed double (211) + (112) of the ε-phase. Texture are persist during annealing 60 °С for 2 hours. The microhardness of the alloy Bi32In41Sn27 foils monotonically increases with increasing expose time at room temperature and reaches saturation. Subsequent isothermal annealing at 60 °С leads to a microhardness value equal to it of massive sample. The distribution of components in the solder joint between copper plates was investigated. Indium and tin diffuse into the copper plates. The depth of penetration of copper into the joint reaches 3 micrometers. When the soldered copper plates are strained, the breakdown on the junction occurs at 790  N and absolute value of the deformation is 0.8 mm. The conducted investigations of copper solder joints indicate the possible practical use of the alloy Bi32In41Sn27 foil as a solder.