Dry wear behaviour and its relation to microstructure of novel 6092 aluminium alloy-Ni{sub}3Al powder metallurgy composite

摘要

Novel aluminium alloy matrix composites reinforced by 15 vol.% Ni{sub}3Al intermetallic particles were prepared by a powder metallurgy route. The 6092 aluminium alloy was produced by gas atomisation, followed by blending with Ni{sub}3Al particles. Consolidation by extrusion at 515℃, with an extrusion ratio of 30:1, produced a uniform distribution of Ni{sub}3Al in the Al alloy matrix. The wear properties of the aluminium alloy-Ni{sub}3Al composites and the monoliths were examined by dry sliding against an M2 steel counterface at 0.94 m/s and a load in the range 42-140 N in a block-on-ring configuration. At 42 and 91 N, the composites offered superior wear resistance to the monoliths. Although, some surface deformation occurred at 42 N, the Ni{sub}3Al largely retained its original shape, allowing it to act as a load-supporting reinforcement. At the highest load (140 N), the monolith offered superior wear resistance to the composite. Gross plastic deformation was observed at the worn surface of the composite, resulting in severe fragmentation of the Ni3Al. A mechanically mixed layer (MML) was observed for both materials at all loads, the thickness of which increased from ～25 μm at 42 N for both materials to ～80 μm for the monolith and ～40 μm for the composite at 140 N. Transmission electron microscopy (TEM) of MML identified a complex structure comprising an amorphous phase containing Al, O, a nanoscale Fe-, Al-, O-based phase, found mainly in the monolith, and in the composite, Ni{sub}3Al fragmented down to the nanometre scale. A linear relationship was found between the wear rate (mm{sup}3/m) and the depth of deformation, with a similar relationship being observed for both composite and monolith. The relationships between wear rate, surface structural changes and starting microstructure are discussed.