Metallurgical problems associated with the production of aluminium-tin alloys

Abstract

Of all the plain bearing alloys available, aluminium alloys have a better combination of ideal bearing characteristics than any other single material. Conventional Babbit alloys, especially the lead bronzes are increasingly being replaced by aluminium alloys, particularly in the automobile industry. It has been known, that the addition of elements, like tin or lead, improves the antiscoring and antifrictional properties of aluminium. Aluminium tin alloys have a wide miscibility gap in the molten state and are virtually insoluble in each other during solidification. Further difficulties arise from the large freezing range of the alloys, which together with the wide density difference between the two components greatly increase the tin segregation during alloy preparation. It has, therefore, been difficult to introduce and uniformly disperse tin in aluminium to the desired extent by conventional melting and casting techniques. The present authors have developed a simple foundry technique which has been used successfully to disperse and retain tin at contents up to 20 wt% in aluminium ingots, which is the subject of the present paper.