Recommended values for the βSn solidus line in Sn-Bi alloys

Sn-Bi is an industrially important system that is often incorporated into multicomponent solder alloys. Despite a large body of experimental work, the reported data are in significant disagreement over the beta Sn solidus line and maximum solubility of Bi in beta Sn. These inconsistencies are often adopted in thermodynamic assessments and databases and might result in the incorrect design of Bi-containing solders. The present study re-measures the beta Sn solidus line using DSC techniques, explores the origin of the inconsistencies in past measurements, and provides recommended values. The work highlights the importance of the equilibration methods used for solidus measurements and discusses methods to test for full homogenisation.