Structure and Microhardness of (Sn₄In)_{100 – х}Bi_x (x = 0–8 аt %) Alloys Produced by High-Speed Cooling

Abstract

The phase composition, microstructure, mechanical properties and stability of foils of (Sn₄In)_100–хBi_x (х = 0–8 at %) alloys synthesized by the method of ultrafast quenching from the melt at cooling rates up to 10⁵ K/s are studied. Rapidly hardened foils of (In₄Sn)_100–хBi_x alloys at a bismuth concentration of less than 4 at % consist of solid solutions of bismuth in the γ phase (Sn₄In) and tin, and foils of the (In₄Sn)₉₂Bi₈ alloy consist of a solid solution of bismuth in the γ phase and tin, as well as the ε phase (BiIn). During aging of the foils at room temperature, the size of inclusions of the ε phase increases due to the decomposition of supersaturated solid solutions of bismuth in the γ phase (Sn₄In) and tin. The studied foils have a microcrystalline structure. The difference in the shape and size of the grains on the side of the foil adjacent to the crystallizer and the freely solidifying side is revealed. The texture of the γ phase in foils depends on the concentration of bismuth. Doping of the γ phase with bismuth leads to an increase in microhardness. Aging of the (InSn)_100–хBi_x (x = 0, 2 and 4 at %) foils at room temperature for 30 h causes a steady increase in the microhardness.