Effects of the liquid phase on tensile elongation of Al-Bi alloy

Tensile tests were performed in Al-Bi alloys in order to show experimental evidences of elongation enhancement by a liquid phase and to understand its underlying causes. Peak elongation of 150-200% was obtained above the melting temperature (539 K) of Bi dispersoids, indicating that the liquid phase can enhance tensile elongation. It was found that homogeneous dispersion of liquid needs to be maintained during deformation. Otherwise, the liquid phase would agglomerate along perpendicular grain boundaries to the tensile axis, causing grain-boundary fracture. When elongation enhancement by the liquid phase was observed, the dislocation density was low and the cavity volume fraction increased slowly, resulting in the delay of cavitation failure. The role of the liquid phase on elongation enhancement was considered to be accommodation of stress concentration and delay in cavitation.