Laser‑Induced Microstructural Refinement and Oxidation Performance in Al–Ce and Al–Ce–Cr Alloys

Laser surface remelting (LSR) has emerged as an effective strategy to refine microstructures and enhance surface properties of aluminum alloys. However, its application remains limited to Al–Ce-based systems, particularly regarding microstructural coarsening evolution within the melt pool and oxidation behavior at elevated temperatures. In this context, this study investigates the influence of the LSR parameters on the microstructural evolution, microhardness, and oxidation of the Al–13Ce and Al–10Ce–1Cr (wt.%) alloys. Directionally solidified substrates were processed using single-track and overlaid-track LSR under different heat inputs (1.7–10 J/mm), and the resulting melt pool morphologies and cellular microstructures were characterized by Scanning Electron Microscopy and Energy-dispersive X-ray spectroscopy. Vickers microhardness measurements were performed on the remelted regions, while oxidation behavior was evaluated by mass gain analysis during isothermal exposure at 640, 680, and 700 °C for up to 96 h. The results show that decreasing heat input leads to progressively shallower melt pools and significant refinement of cellular spacing in both alloys, with the Cr-containing alloy consistently exhibiting finer microstructures due to partial Cr dilution and segregation during rapid solidification. Laser-induced refinement resulted in an increase in microhardness, reaching values approximately three times higher than those of the as-cast microstructures. Although Cr addition refined the cellular microstructure after LSR and was effective in limiting oxide-layer growth at lower temperatures (up to ~ 680 °C), this effect decreased at higher temperatures (700 °C). It was observed that oxidation depended on microstructure and temperature: under fully solid conditions (640 °C), Cr prevented mass gain by forming protective Cr- and Al-rich oxides, while at ≥ 680 °C eutectic melting caused oxide spallation and loss.