Effects of wetting on the compression creep behaviour of metals containing low melting intergranular phases

Abstract

The creep behaviour of several metallic alloys containing low melting intergranular phases has been characterized in experiments performed in uniaxial compression. The alloys included Al-3% Bi-0.35% Ti, Al-8.4% Sn, Al-33% Sn, and Cu-10% Bi. By performing creep tests above and below the melting point, it was found that melting of the intergranular phase has virtually no effect on the creep behaviour of the first three materials (the aluminium alloys); they creep in a manner very similar to that of pure aluminium, and generally behave as if no second phase were present at all. On the other hand, significant changes in behaviour occur in the Cu-10% Bi alloy. Melting of the intergranular phase both enhances the rate of creep and promotes tertiary creep and failure. The creep characteristics of the materials are discussed in terms of the wetting of the liquid phase on the solid grain boundaries and the fractional area of the boundary occupied by the liquid. It is suggested that a significant portion of the grain boundary area, in excess of 70%, must be wet before the liquid influences the compression creep behaviour in a significant way.