Iranian Journal of Materials Science and Engineering

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In this study, aluminum matrix composites reinforced with Al₂O₃ and SiC nanoparticles, and graphene nanoplatelets produced by Spark Plasma Sintering (SPS) were studied. The microstructural and mechanical properties of the composites were evaluated by changing the amounts of the reinforcing materials. The SEM images showed that the reinforcing particles were more distributed in the grain boundary regions. According to the results, the addition of alumina and SiC to the matrix caused an increase in the composite density whereas the composite density decreased by adding graphene nanoplatelets. The highest relative density of 96.3% was obtained for the composite containing 2 wt% Al₂O₃. The presence of the reinforcing particles increased the hardness of all the samples compared to the pure aluminum (39 HV). The composite containing 1 wt.% Al₂O₃, 0.7 wt.% SiC, and 0.3 wt.% graphene showed the highest hardness of 79 HV. Moreover, the plastic deformation of the specimens decreased and the slope of the plastic region increased by adding the reinforcing particles to the matrix.

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Pressureless sintering was employed at 1400 °C to synthesize Ti matrix composites (TMCs) reinforced with in-situ TiB and TiC reinforcements using TiB₂ and B₄C initial reinforcements. The microstructure and wear behavior of the synthesized composites were evaluated and compared and the results showed that B₄C caused the formation of TiB-TiC in-situ hybrid reinforcements in the Ti matrix. Also, TiB was in the form of blades/needles and whiskers, and TiC was almost equiaxed. Moreover, the volume fraction of the in-situ formed reinforcement using B₄C was much higher than that formed using TiB₂. In addition, although the hardness of the B₄C-synthesized composites was higher, the composite synthesized using 3 wt.% TiB₂ exhibited the highest hardness (425 HV). The wear test results showed that the sample synthesized using 3 wt.% TiB₂ showed the lowest wear rate at 50 N, mainly because of its higher hardness. The dominant wear mechanism in the samples synthesized using 3 wt.% B₄C was abrasive and delamination at 50 N and 100 N, respectively while in the samples synthesized 3 wt.% TiB₂, a combination of delamination and adhesive wear and adhesive wear was ruling, respectively.