RETRACTED ARTICLE: Microstructure and mechanical behavior of A356/SiC/Fly-ash hybrid composites produced by electromagne
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TECHNICAL PAPER
Microstructure and mechanical behavior of A356/SiC/Fly-ash hybrid composites produced by electromagnetic stir casting Shashi Prakash Dwivedi • Satpal Sharma Raghvendra Kumar Mishra
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Received: 8 August 2013 / Accepted: 12 February 2014 Ó The Brazilian Society of Mechanical Sciences and Engineering 2014
Abstract Electromagnetic stir casting is one of the simplest ways of producing defect free aluminum matrix composites. This work focuses on the fabrication of aluminum matrix composites reinforced with various weight percentages of SiC particulates and Fly-ash by modified electromagnetic stir casting route. The distribution of SiC and Fly-ash particles in the matrix was improved by providing externally argon gas into the melt during electromagnetic stirring. Five samples of hybrid composite with different combination of Fly-ash and SiC (25 lm) were prepared by electromagnetic stir casting method. Mechanical properties (tensile strength, hardness, toughness and fatigue strength) and microstructure of all five samples were analyzed. Microstructure presents that the reinforcements (SiC particulates and Fly-ash) are uniformly distributed in the matrix (A356). The results reveal that sample of A356/15 %SiC/5 % Fly-ash shows best result among all the selected samples. Density, porosity, specific strength and thermal expansion were also calculated to see the effect of Fly-ash addition. Keywords Fly-ash Electromagnetic stir casting Microstructure Porosity Specific strength Thermal expansion 1 Introduction Hypereutectic aluminum–silicon (Al–Si) alloys are widely applied in aerospace, automobile and electronic industries Technical editor: Alexandre Mendes Abrao. S. P. Dwivedi (&) S. Sharma R. K. Mishra School of Engineering, Gautam Buddha University, Greater Noida, Gautam Buddha Nagar, Uttar Pradesh 201308, India e-mail: [email protected]
due to their excellent wear and corrosion resistance, low density, low coefficient of thermal expansion, good strength and castability. The common microstructure of hypereutectic Al–Si alloys is composed of primary silicon particles. The high strength and wear resistance of these alloys are attributed to the presence of hard silicon particles [1]. The forming based semi-solid phase has attracted great attention as a new technology since it complemented the shortcomings of the current forming processes. The morphology of the primary phase of semi-solid metals plays a very important role in the quality control of semi-solid process. Electromagnetic stirring (EMS) is a forming process which fills the mold cavity through injecting cylinder with semi-solid slurry after uniformly transformed dendritic microstructure formed during solidification process to spherical primary-Al phase particles and distributing it into eutectic phase, by strongly stirring the melt at the initial stage of solidification. The EMS needs to be a good substitute system of mechanical stirring to avoid alloy contamination and damage of stirrer. The rheology forming is controlled b
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