Tailoring Thermal and Mechanical Properties of LPBF AlSi10Cu8Mg Alloy through Advanced Heat Treatment

Laser Powder Bed Fusion (LPBF) additive manufacturing enables the production of high-strength aluminum alloys with complex geometries. However, effective thermal post-treatments are essential to optimize their mechanical performance for industrial applications. This thesis investigates a modified AlSi10Mg alloy with 8% Cu (AlSi10Mg+8Cu) processed via LPBF, with the objective of tailoring its thermal and mechanical properties through an advanced heat treatment approach. Specifically, the study aims to develop an energy-efficient aging procedure that enhances ductility without significantly compromising hardness, thereby expanding the alloy’s suitability for lightweight structural applications. To this end, a low-temperature artificial aging strategy (T5 treatment) was developed and experimentally assessed. LPBF-fabricated samples were aged at 140 °C and 160 °C for various durations. The research methodology integrates differential scanning calorimetry (DSC) to investigate precipitation behavior, optical and scanning electron microscopy (OM and SEM) for microstructural analysis, and mechanical testing, namely microhardness measurements and tensile tests, to evaluate changes of properties . This approach responds to the need for post-processing treatments specifically adapted to the unique, rapidly solidified microstructures characteristic of additively manufactured alloys, which differ significantly from those produced by conventional casting or wrought processes. Aging at 140 °C resulted in gradual strengthening, with hardness increasing from approximately 177 HV to 189 HV after 12 hours, followed by a decline to around 180 HV after 24 hours due to over aging. In contrast, aging at 160 °C produced a more rapid response, achieving a peak hardness of ~191 HV after 10 hours, but also exhibited a sharper drop to ~179 HV with extended aging. The enhanced hardness was attributed to the formation of finely dispersed, nanometer-scale Al₂Cu (θ) and Si precipitates within the aluminum matrix. The LPBF-fabricated microstructure demonstrated excellent thermal stability under these low-temperature aging conditions. Notably, high duration ageing revealed a more uniform distribution of the Cu and Si particles along the melt pool both within the α-Al matrix and along the cell boundaries. The findings of this study, provides new insights into the precipitation behavior of high-copper Al–Si–Mg alloys under sub-solvus aging conditions, thereby advancing the understanding of phase transformations in additively manufactured aluminum systems. The results demonstrate that low-temperature, extended-duration aging can effectively enhance the hardness of LPBF-fabricated alloys without detrimental changes to their microstructure. This confirms the feasibility of using simple, energy-efficient post-processing techniques to improve the mechanical performance of aluminum parts produced via additive manufacturing. Such approaches are aligned with industrial sustainability goals and may accelerate the adoption of LPBF AlSi10Mg+8Cu components in high-performance applications where weight, strength, and cost efficiency are critical. In conclusion, this thesis lays a foundation for tailoring thermal post-processing in LPBF-fabricated AlSi10Mg+8Cu alloys, showing that appropriate aging treatments can significantly improve mechanical performance and structural reliability.