Phase Stability and Mechanical Behavior of Ternary Bismuth-Lead-Tin Solders

Abstract

AbstractResults from a phase stability study of the Bi-Pb-Sn ternary system and mechanical property data from the testing of the Bi-Pb-Sn ternary eutectic alloy are reported. It is found that the mechanical properties of the ternary eutectic alloy change considerably during cooling due to a solid state phase change at 79° C. After solidification, but prior to this phase transformation, the alloy exhibits brittle failure upon tensile loading. After the phase change high ductility is observed, bordering on superplasticity at low strain rates. Furthermore, having gone through the phase change once, the alloy remains ductile even after it is held at temperatures above 79° C. These results are interpreted in terms of the microstructures observed in the alloy.