Microstructure and mechanical properties of AlSi10Mg composite fabricated by laser powder bed fusion

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Abstract

Laser Powder Bed Fusion (LPBF) is suitable to produce complex and intricate Aluminium (Al) alloys components, which preserve high specific strength, outstanding thermal and electrical conductivities, and corrosion resistance. However, the mechanical properties of current LPBF Al alloy materials are still limited due to defects such as voids, cracks and coarse columnar grains.
This study proposed a novel hybrid Al composite (AlSi10Mg + 0.25 wt.% GNP + 10 wt.% SiC) comprising hybrid reinforcements of 0.25 wt.% Graphene Nanoplatelets (GNP) and 10 wt.% Silicon Carbide (SiC) with AlSi10Mg as the matrix. Instead of pre-melting, pre-mixing powders with uniform distribution of the distinct reinforcements inside the AlSi10Mg matrix were produced as raw material by ball milling for the Al composite. The bare AlSi10Mg, AlSi10Mg/GNP, AlSi10Mg/SiC, and AlSi10Mg/GNP/SiC were then produced separately by LPBF under the same laser linear energy density to prove the advantages of the hybrid reinforcements GNP/SiC on the microstructure and mechanical properties of the Al composite. The AlSi10Mg/GNP/SiC was produced by LPBF under varying laser linear energy densities to investigate the optimal microstructure and mechanical properties of the hybrid Al composite. The microstructures of raw powder mixings and produced Al composites were characterized by SEM, EDS, EBSD, and XRD, while the mechanical properties of those were measured in terms of tensile strength and hardness.
The results show that the irregular shape of SiC hinders the even distribution of GNP inside AlSi10Mg, resulting in multiple macro- and micro-pores and cracks inside the hybrid AlSi10Mg composites. Both GNP and SiC are beneficial to refine the grain size inside the hybrid AlSi10Mg/GNP/SiC composite. SiC was found lack of fusion with inadequate wettability between the AlSi10Mg matrix. Though reinforced, the proposed AlSi10Mg/GNP/SiC composite exhibits brittle mechanical behaviour, and its hardness (192 HV10), Young’s modulus (76.21 GPa/mm2), tensile strength (312.72 MPa), and elongation percentage (0.32%) are located in between AlSi10Mg/GNP and AlSi10Mg/SiC. The process parameters were further optimized with an elevated laser linear energy density of 90.02 J/mm3, achieving a relative density of 101.65%. This results in an increased Vicker’s hardness of 195 (HV10) compared to the previous hybrid composite. Furthermore, the quantity of equiaxed grain shapes increases due to elevated temperatures during melting, as evidenced near the melt pole. The study provides a guidance to explore the costumed microstructure and mechanical properties of AlSi10Mg composites by LPBF.

Date of Award	18 Jul 2026
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Yi Nie (Supervisor) & Nai Yeen Gavin Lai (Supervisor)