Tensile Properties of Bi Alloys and a Case Study for Alloy Design in Their Application to High Temperature Solders

Abstract

The s-orbital energy levels (Mk) of some alloying elements in a Bi cluster model were obtained on the basis of the molecular orbital calculation. In contrast, binary Bi-Cu/-Ag/-Zn system alloys with ΔMk of 0.013–0.343 were manufactured and tension- or hardness-tested, where ΔMk was the compositional average of Mk. The ultimate tensile strength and hardness were improved as alloying elements were added and increased in alloys. There was the relation between the ultimate tensile strength, fracture strain or hardness and ΔMk. Further, the compositions of Bi-2.0Ag-0.5Cu (ΔMk: 0.180), Bi-5.0Ag-0.5Cu (ΔMk: 0.379) and Bi-0.25Cu-0.25Sb (ΔMk: 0.044) were proposed as ternary alloys. It is found that the ultimate tensile strength, fracture strain and hardness values of ternary alloys could be also able to predict using their estimation lines obtained from binary Bi system alloys.