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Stir casting is employed for successful casting of aluminum-based metal matrix composite (MMC) plates of 12 mm thickness. Surface imperfections, porosity and reinforcement agglomeration are the main concerns in stir casting processes. Solid state friction stir processing (FSP) enhances mechanical characteristics by grain refinement and uniform distribution of reinforcement of MMC. Some of the crucial specifications of FSP include the tool traverse speed, tool rotational speed, tool shoulder diameter (D/d) ratio, pin design, pin length and axial force. In this investigation, five varying tool traverse speeds ranging between 20 mm and 60 mm per min were experimented on the stir cast plates. The wear rate, microstructure and microhardness evaluation on FSP plates revealed that wear resistance of 40 mm/min tool traverse speed FSP plate is superior and attribute to significant microhardness values. In addition, fine grains, uniform distribution and SiC particle bonding with aluminum matrix contribute to effective resistance to wear.

Friction stir processing is demonstrated to effectively enhance the surface and bulk properties of aluminum composites fabricated via the stir casting route. This process is performed below the melting point of the base material wherein common conventional fabrication problems such as solidification, liquidation cracking, and porosity are eliminated to a significant extent. Five different tools with varying tool diameter ratios are experimented on while maintaining tool rotational and traverse speeds and axial force constant. In this investigation, the hardness and wear characteristics of the LM25 aluminum alloy reinforced with 5% silicon carbide particles composite is studied. It is concluded that the tool with a tool diameter ratio of 3.0 resulted in a defect-free processing zone, refined grains, and a minimum particle size enhancing the wear resistance and hardness as compared to that for other values of a tool diameter ratio.

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