Effect of powder size and sintering time on the induction sintering behavior of aluminum fabricated by UHFIS

This study systematically investigates the effects of powder particle size and sintering duration on the mechanical and microstructural behavior of pure aluminum fabricated using the ultra-high-frequency induction sintering (UHFIS) technique. Five different powder sizes (100, 75, 50, 30, and 15 µm) and three sintering times (60, 180, and 300 s) were applied at a constant temperature of 550 °C. Vickers hardness measurements and SEM observations demonstrated that finer powders, particularly 15 and 30 µm, yielded more homogeneous and denser microstructures with reduced porosity and higher hardness values compared to coarser powders. The maximum hardness of 32.81 HV was achieved under the 15 µm–180 s condition, whereas larger powders (100 µm) exhibited limited densification and lower hardness (25.72 HV). Energy consumption analysis revealed that finer powders exhibited approximately 15% higher energy usage compared to coaser powders, due to their larger specific surface area and increased number of interparticle contacts, despite providing enhanced densification efficiency. Furthermore, microstructural evaluations confirmed that a sintering time of 180 s provided the optimal balance between densification and grain growth. Shorter durations resulted in insufficient neck formation, while prolonged sintering promoted coarsening-induced softening. This work highlights the critical interaction between powder size and sintering time, providing quantitative insights into the densification-energy correlation. The findings suggest that UHFIS is a promising and energy-efficient technique for tailoring the processing of lightweight aluminum-based materials and composites for advanced structural applications.