Influence of heat treatment on the high-cycle fatigue properties and fatigue damage mechanism of selective laser melted AlSi10Mg alloy

Abstract

The high-cycle fatigue properties and fatigue damage mechanism of AlSi10Mg alloy manufactured by selective laser melting (SLM) were investigated. The influence of the post-heat treatment on the microstructure and high-cycle fatigue properties was also examined. The SLM-manufactured AlSi10Mg alloy was heat-treated under two different conditions, namely T6 and direct aging (DA). The results of the high-cycle fatigue tests, which were carried out at room temperature, imply that, under all three conditions (as-built, T6, DA), the fatigue strength decreases as the number of cycles increases along with the estimated endurance limit. Predominantly, the fatigue properties were influenced by the morphology and size of the Si particles, both controlled by adjusting the heat treatment. The alloy that was processed using DA heat treatment had superior fatigue properties due to its cellular structural morphology characterized by a significant amount of fine Si precipitates. Compared with the as-built and T6 specimens, the superior fatigue limit of the DA alloy is attributable to its outstanding strength characteristics. The reliability of the fatigue life of the DA alloy is relatively high. Fatigue fracture samples revealed that the DA alloy had evenly distributed dislocations along the cellular boundaries. The fine Si particles were found to play an important role in preventing fatigue crack propagation, thereby enhancing fatigue properties. The effect of the heat treatment on the microstructure and mechanical properties of the SLM AlSi10Mg specimens was investigated with a specific focus on fatigue strength. The results highlighted that an appropriate DA process could significantly enhance the fatigue performance of the AlSi10Mg alloy under investigation. The resulting characteristics are highly advantageous and are superior to those obtained with other conventional heat treatment processes.