Microstructure formation and mechanical performance of micro-nanoscale ceramic reinforced aluminum matrix composites manufactured by laser powder bed fusion

Abstract

The constituent ratio merged into as-fabricated composites can directly influence the content of in-situ formed reinforcing phases, which is closely related to the mechanical performance of these composites. In this work, aluminum matrix composites reinforced with 10, 15, and 20 wt% (ZrC+TiC) ceramic fractions have been manufactured by laser powder bed fusion (LPBF) additive manufacturing. The effect of hybrid ceramic reinforcement content on laser absorption behavior, fabrication and fraction of micro-nanoscale reinforcing phases, mechanical performance of the as-fabricated aluminum matrix composites is studied. In the laser processing, TiC reacts with ZrC to synthesize interfacial layer on the unmolten ceramic particals and precipitate nano-particles. With the hybrid ceramic content raising from 10 to 20 wt%, the laser absorption behavior is enhanced, and the nano-particle fraction increases. The micro/nano hardness of the composites with 20 wt% ceramic content, reaches 120 HV0.2 and 1.33 GPa, respectively. An elastic modulus of ∼94.4 GPa and tensile strength of ∼280 MPa are obtained for the 15 wt% (ZrC+TiC)/Al composites, much higher than those of the unreinforced Al matrix. This is attributed to the combination of formation of nano-precipitates and coherent bonding at the reinforcement/matrix interfaces in these composites.