Soft particles assisted grain refinement and strengthening of an Al-Bi-Zn alloy subjected to ECAP

With the aim to improve the strength of potential Pb-free Al-Bi based bearing alloys, an Al-6Bi-8Zn alloy was subjected to equal channel angular pressing (ECAP). To reveal the roles played by the soft Bi particles, an Al-8Zn alloy is compared. After five passes of ECAP (5P), ultrafine grained (UFG) microstructures are obtained in both alloys, while most of the Bi particles are deformed into the flake shapes. The yield strength (YS) of the as-deformed Al-6Bi-8Zn sample is more than three times as that of the as-cast sample. The influence of soft Bi particles on the deformation during ECAP and the final mechanical properties of the Al-6Bi-8Zn alloy are discussed. It is revealed that soft Bi particles have a strong influence on enhancing grain refinement during ECAP. At the same time, ECAP is found to accelerate the precipitation of the β(Zn) phase along grain boundaries (GBs).