Hybrid metal matrix composites (HMMC’s) are next generation metal matrix composite materials that have the potential of gratifying recent demands of advanced energy applications in the field of aerospace, automobile and biomedical. The MMC’s have to work at elevated temperature or vacuum environment where lubrication using liquid lubricants is ineffective or difficult to achieve; moreover, liquid lubricants are not environmental friendly, since they releases pollutants into environment. Solid lubricants such as graphite, CNT’s, MoS2and graphene have been widely used as secondary reinforcements to meet such operational needs by fabricating green or environmental friendly self lubricating HMMC’s. This article outlines recent advances in the area of self lubricating HMMC’s reinforced with graphite as secondary reinforcement. The focus of the study was on mechanical and tribological behavior of Aluminum and magnesium based self lubricating HMMC’s. The effect of graphite, different hybrid reinforcements and their strengthening mechanisms are also discussed in detail.
Magnesium hybrid composites are a new class of lightweight metal matrix composites having excellent physical, mechanical, wear and corrosive properties. Hybrid magnesium matrix composites are fabricated using different combinations of reinforcements having basics properties like wear resistance and high strength of ceramics, self-lubricating of graphite, MoS2, CNT, and graphene, high thermal conductivity of carbon, diamond, and cubic boron nitride, and low cost of fly ash. This article presents an overview of different combinations of reinforcements used for fabrication of hybrid magnesium matrix composites and their effects on the mechanical and tribological properties of the hybrid materials. The major issues like agglomeration, interfacial phenomena, reinforcement–matrix bonding, and problems related to uniform distribution of particles are discussed in this article. Magnesium hybrid composites have the potential of satisfying the recent demands of aerospace, automobile, biomedical, defense, marine, and electronics industries. The future directions and potential research areas in the field of magnesium hybrid composites are also highlighted.
This article statistically investigates the effect of various parameters such as material factors: silicon carbide (SiC) reinforcement, graphite (Gr) reinforcement and mechanical factors: normal load, sliding distance and speed on the sliding wear rate of vacuum stir cast self-lubricating AZ91D-SiC-Gr hybrid magnesium composites. The sliding wear tests have been performed on pin-on-disc tribometer at 10-50N loads, 1-3m/s sliding speed and 1000-2000m sliding distance. It has been examined that hybrid composites yielded improved wear resistance with reinforcement of SiC and solid lubricant graphite. ANOVA and signal-to-noise ratio investigation indicated that applied load was the most critical factor influencing the wear rate, followed by sliding distance. Further, the AZ91D/5SiC/5Gr hybrid composite has exhibited the best wear properties. From the SEM and EDS analysis of worn surfaces, delamination was confirmed as the dominant wear mechanism for AZ91D-SiC-Gr hybrid composites.
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