Microstructure and wear characteristics of rapidly solidified Al-Pb-Cu alloys

The microstructure and wear properties of rapidly solidified Al-XPb (X = 10, 16 and 20 wt.%) and Al-16Pb-Y (Y = 4Cu or 4Cu-1Mg) alloy powders were investigated. In order to overcome the constraint of the miscibility gap between Al and Pb under equilibrium conditions, both in the solid and the liquid states, the alloys were rapidly solidified to produce them in a segregation-free condition. Although the Pb particles showed relatively fine dispersion in the Al matrix in all the alloys by this process, the Al-16Pb alloy was found to have the most favorable microstructure with discrete Pb particles of about 0.5 mu m size. With the addition of Cu and Cu-Mg to Al-16Pb, cellular structures were newly formed, not seen in the binary AI-Pb alloys. Wear properties of the Al-Pb binary alloys measured as a function of the sliding speed, sliding distance, and applied load showed that the Al-16Pb alloy has the best wear resistance, as expected from the fine microstructural features in this alloy. The wear resistance of the alloys containing Cu- and Cu-Mg was higher than that of the Al-16Pb alloy, due to the matrix strengthening by precipitation hardening. The wear mechanism was identified by examining the wear traces and wear debris. (C) 2000 Elsevier Science S.A. All rights reserved.