Improving wear performance of dual-scale Al-Sn alloys: The role of Mg addition in enhancing Sn distribution and tribolayer stability

The dual-scale structured Al-Sn based alloys are potential alternative for journal bearings of automotive application due to their excellent tribological and mechanical properties. In this work, the authors attempted to further promote wear properties of dual-scale structured Al-12 wt% Sn alloys by Mg addition. It has been found that appropriate Mg addition could increase wet-ability and reduce divorced Sn eutectics, resulting improved distribution of Sn phase, strength and ductility. Moreover, the mechanism for the improvement of the wear properties of Mg-containing Al-Sn alloy was revealed, and could be summarized as follows: (1) The improved transportation and distribution of the Sn nanophases, including nanoparticles and nanowires, towards the worn surface effectively reduced the friction coefficient; (2) enhanced Mg-oxide film and tribolayer formation on the mating surfaces and (3) increased stability of tribolayer owing to better combination of the strength and ductility. But excessive Mg addition led to too high amount of Mg2Sn and Mg17Al12 intermetallic phases, which worsen the wear properties. The dual-scale CG-30 Al-Sn with 1.2 wt% Mg addition exhibits the best wear performance under the present experiment conditions.