Mechanistic understanding of strengthening in a novel MXene/AlSi10Mg matrix composite processed by laser powder bed fusion

Abstract

The fabrication of high-performance two-dimensional nanosheets strengthened Al matrix composites (AMCs) is challenging due to the agglomeration issue of traditional nanosheets (graphene) and their high reactivity with Al powder. To address these concerns, Ti3C2 MXene nanosheets with superior chemical stability were employed as a substitute for graphene in this study. Furthermore, a novel MXene/AlSi10Mg composite powder for the laser powder bed fusion (LPBF) was synthesized using a powder coating strategy. The approach involves three steps, including intercalation treatment of MXene flakes, uniform dispersion of the delaminated MXene nanosheets in aqueous solution, followed by the powder coating treatment using a solid-liquid fluidized bed. Differing from conventional methods for making powder mixtures, such as mechanical blending and ball milling, our powder coating approach achieved uniform distribution and high purity of MXene on the surface of AlSi10Mg powder, while maintaining the original sphericity and flowability of powder. The MXene-coating exhibited exceptional stability under intense conditions of high-energy laser exposure and high-temperature Al melt, enabling the successful retention of MXene nanosheets after LPBF processing. Experimental results show that the retained MXene effectively strengthened the Al matrix through load transfer from Al matrix, pinning effect on the movement of grain boundaries, and inhibiting effect on the deformation and fracture of eutectic Si. Consequently, compared to the bare AlSi10Mg sample processed by LPBF, a small addition of MXene (0.25 wt%) yielded a significant improvement in tensile strength (over 60%), while maintaining an acceptable ductility.