Effects of cooling rate and microstructure scale on wear resistance of unidirectionally solidified Al-3.2wt.%Bi-(1; 3) wt.%Pb alloys

Abstract Aluminum alloys with soft elements are quite promising in the automotive industry for manufacturing machine elements subjected to relative motion. The combination of some elements makes it possible to highlight some properties, such as the wear resistance. It is also particularly important to understand the role of the microstructural phases’ representative scale in this property. In this research, the joint influence of Bi and Pb on Al-3.2 wt.%Bi-(1; 3) wt.%Pb alloys is analyzed. The alloys were unidirectionally solidified in a water-cooled experimental device under a wide range of solidification cooling rates. The resulting microstructure is formed by droplets containing both Pb and Bi, disseminated in the Al-rich matrix, whose spacing (λG) and diameter (DG) are shown to vary significantly with the cooling rate. Wear tests carried out on samples with different λG and DG showed that the wear volume (Vd) of those with more refined microstructures was lower. Regarding the alloy’s Pb content, it was shown that the one with higher Pb content (3% Pb) has higher wear resistance (lower Vd) and lower wear coefficients for the examined sliding distances of 207, 415, 622 and 829 m, despite preserving a same alloy hardness of about 25 HV.