The Effect of the Combination of Vibration and Mold Temperature on the Characteristics of Remelted Aluminum

This study investigates the coupled influence of vibration frequency and mold temperature on the solidification behavior and mechanical performance of recycled aluminum derived from automotive wheel scrap. Investment casting was conducted at mold temperatures ranging from 150 to 350 °C while applying mechanical vibration at frequencies between 100 and 250 Hz. Hardness testing, tensile characterization, optical metallography, and multi-scale SEM analysis were employed to evaluate the evolution of microstructure and defects under varying thermo-mechanical conditions. The results show that mechanical properties exhibit a non-linear dependence on vibration frequency, with an optimum window at 100–150 Hz where dendrite fragmentation, eutectic segmentation, and reduced microporosity contribute to enhanced hardness and tensile behavior. Frequencies above 150 Hz induce turbulent melt flow, promoting pore clustering and intermetallic agglomeration that significantly degrade strength. Mold temperature further modulates these effects, where temperatures above 300 °C suppress vibrational refinement due to reduced thermal gradients and grain coarsening. The combined findings demonstrate that microstructural refinement in recycled aluminum can only be achieved when vibration and thermal conditions are simultaneously optimized. This work establishes a clear processing window for vibration-assisted casting of recycled aluminum and provides practical guidance for industrial remelting operations targeting improved sustainability and mechanical reliability.