Abstract
In the present work, we proposed a novel friction stir processing (FSP) to produce a locally reinforced aluminum matrix composite (AMC) by stirring copper-coated SiC particulate reinforcement into Al6061 alloy matrix. Electroless-plating process was applied to deposit the copper surface coating on the SiC particulate reinforcement for the purpose of improving the interfacial adhesion between SiC particles and Al matrix. The core-shell SiC structure provides a layer for the atomic diffusion between aluminum and copper to enhance the cohesion between reinforcing particles and matrix on one hand, the dispersion of fine copper in the Al matrix during FSP provides further dispersive strengthening and solid solution strengthening, on the other hand. Hardness distribution and tensile results across the stir zone validated the novel concept in improving the mechanical properties of AMC that was realized via FSP. Optical microscope (OM) and Transmission Electron Microscopy (TEM) investigations were conducted to investigate the microstructure. Energy dispersive spectrometer (EDS), electron probe micro-analyzer (EPMA), and X-ray diffraction (XRD) were explored to analyze the atomic inter-diffusion and the formation of intermetallic at interface. The possible strengthening mechanisms of the AMC containing Cu-coated SiC particulate reinforcement were interpreted. The concept of strengthening developed in this work may open a new way of fabricating of particulate reinforced metal matrix composites.
Highlights
Aluminum alloys are extensively used for structural applications in aerospace, military, and transportation industries due to their low density, high specific strength, and good corrosion resistance
The fabrication of locally particulate reinforced aluminum matrix composite (AMC) has been realized in the stir zone by friction stir processing of bare SiC particles as well as Cu-coated SiC particles into Al6061 matrix
The lack of Cu-coated SiC particles in the upper 2 mm region in the Stir zone (SZ) may be attributed to a less effective stir that is provided near the probe root adjacent to the shoulder
Summary
Aluminum alloys are extensively used for structural applications in aerospace, military, and transportation industries due to their low density, high specific strength, and good corrosion resistance. Their poor wear resistance has limited their tribological applications. In comparison to aluminum alloys, aluminum matrix composites (AMCs) that were reinforced with discontinuous reinforcements, such as Al2 O3 , TiB2 , or SiC ceramic particles exhibit higher mechanical strength and superior tribological properties [1,2,3,4]. The key parameters of the process are tool geometry, rotating speed, and traverse speed, which have significant effects on the microstructure and mechanical properties [11,12]. A non-consumable rotating tool with a shoulder and Materials 2018, 11, 599; doi:10.3390/ma11040599 www.mdpi.com/journal/materials
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