Surface microstructure tailoring, phase formation, and wear of cast and laser-remelted Al–Mg–Sc alloys

Al–Mg–Sc alloys are promising for aerospace and automotive components that require low density, high strength, and dependable surface durability under sliding/abrasive service, especially when processing creates strong surface-to-core thermal gradients. This study is important because wear performance in these alloys is still insufficiently mapped to solidification cooling rate and processing route, limiting predictive design and potentially affecting component reliability when microstructures form under heterogeneous thermal histories during solidification processing. Methods combine directional solidification (DS) and laser surface remelting (LSR) of an Al–5Mg–0.4Sc alloy (wt.%), while previously prepared Al–5Mg–0.1Sc samples were used for wear and microhardness comparison. In the case of the LSR, heat input and overlapping remelted layers have been systematically varied. The main purpose is to quantify cooling-rate-driven microstructural evolution in both routes, assess how LSR parameters modify remelted-layer morphology, and establish processing-microstructure-wear relationships. LSR produced a marked microstructural transformation, replacing the dendritic substrate by refined cellular/columnar structures and partially dissolving pre-existing interdendritic phases. The remelted regions also exhibited reduced heterogeneity, and elimination of banded defects after overlapping laser passes. In tribological terms, the LSR-treated surfaces exhibited wear rates about 3–4 times lower than the untreated DS substrates, despite only small hardness changes. Overall, the improved wear resistance was mainly associated with induced surface refinement of the microstructure, phase homogenization, and enhanced surface mechanical stability.