Friction and dry sliding wear of Al–Fe–Cr quasicrystals with multi-reinforcements by laser powder bed fusion

A specially designed Al–Fe–Cr alloy with a rapid solidification-induced multi-scaled heterogeneous composite structure was manufactured using a laser powder bed fusion (LPBF) process with a high relative density (over 99.7%) and defect-free features. From the aspect of a single molten pool, the LPBF processed sample presents three regions with distinct composite structures: i) inner laser fusion zone (LFZ); ii) molten pool boundary (MPB) and iii) heat-affected zone (HAZ). For instance, spherical Al–Fe–Cr quasicrystals with sizes ranging from 100 to 300 nm inside ultrafine cellular structures are observed in the laser fusion zone. In contrast, the molten pool boundary exhibits a microstructure containing coarse flower-like quasicrystal particles and rectangular θ-Al₁₃(Fe, Cr)_2-4 particles. Moreover, the finer reinforcements in the heat-affected zone are spherical, rectangular or structureless and disperse in the α-Al matrix. This heterogeneous structure can be attributed to the graded temperature and solidification rate inside a single molten pool during LPBF processing. The tribological performance of the QC-reinforced aluminum matrix nanocomposites was comparatively investigated on a ball-on-disc reciprocating tribometer (UMT Tribo), in which the coefficient of friction was recorded. The results show that the LPBF-processed sample presents a stable friction coefficient (0.548) from mild to severe loads with a higher wear resistance of 3.704 × 10^{- 4}mm³/(N*m) than the other LPBF-processed Al alloys. The worn surface morphology analysis shows that the wear mechanism presents a duplex wear mechanism of adhesive and oxidation wear.