Fabrication of High-Strength Al/SiC p Nanocomposite Sheets by Accumulative Roll Bonding
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DURING the last two decades, the application of metal matrix composites (MMCs) in aerospace, military, and automotive industries has increased. This is due to some properties such as the high ratio of strength to density, improved elastic modulus, high wear resistance, high thermal conductivity, and excellent corrosion resistance.[1–3] Aluminum and its alloys with properties such as light weight, high strength, low thermal expansion coefficient, and good corrosion resistance are the most widely used materials in MMCs as matrix.[4] Moreover, the capability of using several types of reinforcements in aluminum matrix composites is the most important advantage of aluminum.[1,4] The reinforcements are in the form of continuous fibers, whiskers, platelets, or particulates.[1] Among aluminum matrix composites, aluminum reinforced by particulate silicon carbide was the subject of several research studies.[1–3] It was reported that using nanosize particles as reinforcement by the promoting particulate hardening mechanism can considerably improve the mechanical properties.[5–8] Nanoparticulate-reinforced MMCs were produced by several fabrication techniques including mechanical alloying,[7] sintering,[9] ultrasonic casting,[8] etc. The main problems in these methods are high production cost, high energy consumption, and the M. REZAYAT, Graduate Student, and A. AKBARZADEH, Associate Professor, are with the Department of Materials Science and Engineering, Sharif University of Technology, Tehran 11155-9466, Iran. A. OWHADI, Associate Professor, is with the School of Railway Engineering, Iran University of Technology, Tehran, Iran. Contact e-mail: [email protected] Manuscript submitted August 9, 2011. Article published online February 22, 2012 METALLURGICAL AND MATERIALS TRANSACTIONS A
presence of defects such as particle agglomeration and formation of brittle phase during the production process. So, in order to reduce these problems, several fabrication methods were developed during the last few years. Recently, accumulative roll bonding (ARB) was introduced as a new method to produce particlereinforced MMCs. Combining the two concepts of production of ultrafine grain structures by the ARB process and using reinforcing particles in the matrix leads to production of high-strength sheets.[10] This method has two steps. At the first step, the roll-bonding process is carried out to impose appropriate reinforcement particles into the base metal. For this purpose, two sheets are degreased and brushed and the powder is deposited on the surface of one sheet and then the sheets are stacked and roll bonded. At the next step, the ARB process is carried out to improve the dispersion of reinforcement particles in the base metal and to produce an ultrafine grain structure. For repeating roll bonding after surface treatment, the two sheets are stacked and then rolled.[10–12] Kitazono et al.[12] used this method to manufacture the closed-cell aluminum foams. In the work by Lee et al.,[13] Al/SiCp composite was processed by ARB to obtain ult
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