Preparation and mechanical behavior of Co‐based hard particles reinforced aluminum matrix composites.

To address the issues of existing powder metallurgy particle reinforced composites, such as poor wettability between ceramic reinforcement and Al matrix, the toxicity of quasicrystal, the compositional limitations of high entropy alloy, and poor thermal stability of amorphous alloy reinforcement, etc. Al matrix composites reinforced with Co-based hard particles (M7) were synthesized by a powder metallurgy process. The effects of sintering temperature, M7 hard particle content, and particle size on the microstructure and mechanical behavior of the composites were investigated. The results show that as the sintering temperature rises, the interdiffusion reaction between M7 particles and Al matrix is enhanced, the diffusion layer becomes thicker, the in-situ generated intermetallic compounds such as Al 3 Ni 2 , Al 13 Cr 2 , Co 2 Al 9 and Al 72.5 Co 16.5 Ni 11 become more abundant, and parts of M7 particles gradually dissolve in the Al matrix and the interdiffusion layer disappeared. When the sintering temperature was raised from 580°C to 640°C, the microhardness and yield strength were improved from 23.9 to 34.7 HV 0.1 and 40.9–175.2 MPa, respectively. The composites' microhardness and strength increase as the M7 particle content increases. Meanwhile, the smaller the particle size, the greater the microhardness and yield strength. The strengthening mechanism of M7/Al composites is mainly attributed to the synergistic effects of the in-situ generated multiphase intermetallic compounds strengthening, solid solution strengthening, and M7 hard particles dispersion strengthening. Furthermore, the M7/Al composites' microhardness and strength were respectively 27.6% and 146.1% higher than those of the SiC/Al composites containing the same size and content of SiC particles, which is mainly due to the good interfacial wettability between M7 and Al matrix. It indicates that metal-based hard particles could be better alternative reinforcements to produce high performance composites. • Al matrix composites reinforced with Co-based hard particles were synthesized by PM. • There was a significant improvement in the mechanical properties of the M7 /Al composites. • The synergistic reinforcement mechanism for M7 /Al composites is proposed. [ABSTRACT FROM AUTHOR]