摘要
A comparative study on the surface properties of Al-SiC-multi walled carbon nanotubes (CNT) and Al-SiC-graphene nanoplatelets (GNP) hybrid composites fabricated via friction stir processing (FSP) was documented. Microstructural characterization reveals a more homogeneous dispersion of GNPs in the Al matrix as compared to CNTs. Dislocation blockade by SiC and GNP particles along with the defect-free interface between the matrix and reinforcements is also observed. Nanoindentation study reveals a remarkable ~207% and ~27% increment in surface nano-hardness of Al-SiC-GNP and Al-SiC-CNT hybrid composite compared to as-received Al6061 alloy, respectively. On the other hand, the microhardness values of Al-SiC-GNP and Al-SiC-CNT are increased by ~36% and ~17% relative to as-received Al6061 alloy, respectively. Tribological assessment reveals ~56% decrease in the specific wear rate of Al-SiC-GNP hybrid composite, whereas it is increased by ~122% in Al-SiC-CNT composite. The higher strength of Al-SiC-GNP composite is attributed to the mechanical exfoliation of GNPs to few layered graphene (FLG) in the presence of SiC. Also, various mechanisms such as thermal mismatch, grain refinement, and Orowan looping contribute significantly towards the strengthening of composites. Moreover, the formation of tribolayer by the squeezed-out GNP on the surface is responsible for the improved tribological performance of the composites. Raman spectroscopy and various other characterization methods corroborate the results.
对比研究多壁碳纳米管(CNT)和石墨烯纳米片(GNP)对Al-SiC基复合材料表面性能的影响,用搅拌摩擦法分别制备Al-SiC-CNT和Al-SiC-GNP复合材料。显微组织表征表明,与CNTs相比,GNPs在铝基体中的分散更加均匀。此外,还观察到SiC和GNP颗粒对位错的阻碍以及基体与增强材料之间的无缺陷界面。纳米压痕结果表明,与Al6061合金相比,Al-SiC-GNP和Al-SiC-CNT复合材料的表面纳米硬度分别显著提高约207%和27%,显微硬度分别提高了约36%和17%。摩擦学分析表明,Al-SiC-GNP复合材料的比磨损率降低约56%,而Al-SiC-CNT复合材料的比磨损率提高约122%。Al-SiC-GNP复合材料的高强度是由于在SiC存在下,GNPs会机械剥离成几层石墨烯(FLG)。此外,热失配、晶粒细化和Orowan循环等多种机制对复合材料的增强也有重要作用。而摩擦性能提升的主要原因是其表面挤出的GNP形成摩擦层,拉曼光谱和其他表征方法证实这一结果。
