Three dimensional microstructures and wear resistance of Al-Bi immiscible alloys with different grain refiners

Abstract

The three dimensional (3D) microstructures of Al-Bi alloys with different grain refiners (Al-5Ti-B, Al-3B and Al-3Ti) have been studied using synchrotron X-ray microtomography. The relationships between the microstructures and the corresponding wear behavior are verified through the friction and wear tests. The worn surfaces of the samples with grain refiners tested under 15 and 60 N loads are analyzed using Scanning Electron Microscopy (SEM). The results indicate that the addition of grain refiners is beneficial to the size and distribution of the Bi-rich particles in Al-Bi alloys. Compared with Al-5Ti-B and Al-3B grain refiners, the Bi-rich particles are more uniformly distributed and spherical with finer size with the addition of Al-3Ti grain refiner. The refinement renders the Al-20wt%Bi alloy refined by Al-3Ti the superior wear resistance with respect to those refined by Al-5Ti-B and Al-3B grain refiners, corresponding to the microstructures with fine and uniformly distributed Bi-rich particles in the Al matrix.