IDL - International Digital Library Of Technology & Research Volume 1, Issue 3, Apr 2017
Available at: www.dbpublications.org
International e-Journal For Technology And Research-2017
Influence Of Combined Grain Refinement And Modification On Microstructure And Mechanical Properties Of Al-Si18% Alloy. Ashish Dahala, Debesh karkia, Nischal P. Rajbhandaria, ,Kotgi Kotreshb a Department of Mechanical Engineering, NitteMeenakshi Institute of Technology, Bangalore, 560064,India Asst.Proffesor ,Department of Mechanical Engineering, NitteMeenakshi Institute of Technology, Bangalore, 560064,India
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Abstract This paper attempts to investigate the influence of the microstructure and mechanical property changes on Al-Si 18% alloy by combined action of both (Al-TiB2+ Na2SiF6) grain refinement and modification and without grain refinement and modification effect by cooling under three different conditions very fast cooling, moderate cooling and slow cooling.. The microstructures of the castings are studied by optical microscopes. The microstructure and mechanical properties (tensile strength, hardness and wear) was tested of as cast, treated (grain refined and modified) samples. The result demonstrated that significant refinement of ι Al was due to the addition of refiner. Similarly addition was responsible for the modification of Si particles. These refinement and modification in microstructure resulted in improvement of hardness value, tensile strength and resistance for wear. Introduction Al-Si eutectic alloy are the mostly used alloys for industrial applications due to their unique mechanical properties such as high strength to weight ratio and corrosion resistance. In addition, the low coefficient of thermal expansion and good wear resistance make these alloys suitable for manufacture of components such as cylinder blocks and piston [1].Grain refinement is considered to be one of the most important and popular melt treatment processes for aluminum–silicon alloys castings. The use of grainrefiners to improve castings mechanical properties is widespread in aluminium industry, and its associated benefits on final products are well documented [2].The advantages of grain refinement of aluminum alloys are both technical and economic, which include reduced ingot cracking, better ingot homogeneity [3], being less susceptible to hot cracking [4] and mechanical properties are improved significantly. Grain refinement improves the quality of castings by reducing the size of primary ι-Al grains nucleated in the as-cast product, which otherwise will solidify naturally with coarse colaminar grain structure in the absence of grain refiner. Fine equiaxed grain structure is desired because it comes along with several benefits such as uniform IDL - International Digital Library
distribution of second phases and microporosity to improve homo-geneity, improved feeding ability to avoid incomplete filling of mold [5], reduced porosity and the elimination of hot tearing, high yield strength, high toughness, im-proved machinability and excellent deep drawability of the products [6]. The present investigation is an attempt to improve the mechanical properties of Al-Si 18% by cooling under different conditions with and without grain refiner and modifier Al-TiB2& Na2SiF6.The microstructure, tensile strength, wear hardness was studied with and without using grain refiner and modifier.
Fig1. Stir casting setup 1|P a g e
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