New metastable electron phases in binary B-metal alloys

Abstract

Utilizing the splat cooling technique of rapid quenching, nineteen binary B-metal alloy systems were investigated. The following non-equilibrium effects were observed at—190°C; new f.c.c. α phases in the Ag-In, Zn-Ga, and Cd-Sn systems; an extended f.c.c. α phase in Cd-In alloys in the composition range of 20 to 90% In; a new phase with an unknown structure in gallium-rich Zn-Ga alloys; a new simple hexagonal γ phase in Cd-Bi alloys; new phases in binary alloys of Ga with Cu, Ni, and Bi; and shifts in the equilibrium phase boundaries in the In-Sn system. All these non-equilibrium effects disappeared on heating to 20°C. The structural parameters of these phases were determined. The structures of the new metastable phases are determined primarily by the average valence electron concentration (VEC). The f.c.c. phases occur in a VEC range of 2.25–2.45 e/a; simple hexagonal γ phases occur in a VEC range of 3.4–3.9. Factors governing the formation of these phases are discussed.