Influence of heat treatment on the microstructure, hardness and sliding wear of PBF-LB AlSi10Mg across temperature variations

Abstract

Metal additive manufacturing, particularly laser powder bed fusion (PBF-LB), has revolutionized the production of complex geometries with enhanced performance. This study investigates the effects of solution heat-treatment on the microstructure, hardness, and dry sliding wear behavior of PBF-LB manufactured AlSi10Mg alloy. Heat-treatments were performed at 450 °C, 500 °C, and 530 °C for varying durations, followed by water quenching, and designated as HT1, HT2, and HT3. Tribological behavior was assessed using a ball-on-disk tribometer, while microstructural and wear track features were characterized via scanning-electron-microscopy (SEM) and energy-dispersive-spectroscopy (EDS). Microhardness was measured using INNOVATEST-FALCON-507 tester. The as-built alloy exhibited fine cellular microstructure, which coarsened with increasing temperature and duration, leading to reduced silicon segregation and more uniform phase dispersion. An inverse relationship between microhardness and relative density was observed across heat treatment stages, governed by temperature dependent phase transformations and defect evolution. While HT1 and HT2 resulted in significant softening, HT3 showed an anomalous hardness recovery, likely due to precipitation hardening or microstructural stabilization. Relative density decreased at higher temperatures, attributed to pore coalescence and thermal degradation. Wear behavior was strongly influenced by debris generation and microstructural integrity. The as-built condition demonstrated superior wear resistance, characterized by high hardness, minimal volume loss, and stable coefficient of friction (CoF). In contrast, HT1 and HT2 exhibited degraded wear resistance due to increased debris and surface instability. HT3 showed partial recovery in wear performance, correlating with hardness stabilization and reduced defect density. These findings highlight the critical interplay between heat treatment, microstructure, and tribological response, emphasizing the need for optimized thermal post-processing to enhance the wear performance of PBF-LB AlSi10Mg alloys for demanding applications.