V. Vijeesh, 1 M. Ravi, 2 and K. Narayan Prabhu 3 The Effect of the Addition of Strontium and Cerium Modifiers on Microstructure and Mechanical Properties of Hypereutectic Al-Si (LM30) Alloy REFERENCE: Vijeesh, V., Ravi, M., and Prabhu, K. Narayan, “The Effect of the Addition of Strontium and Cerium Modifiers on Microstructure and Mechanical Properties of Hypereutectic Al-Si (LM30) Alloy,” Materials Performance and Characterization, Vol. 2, No. 1, 2013, pp. 296–307, doi:10.1520/MPC20120007. ISSN 2165-3992. ABSTRACT: The present work deals with the melt treatment of LM30 hypereutectic Al-Si alloy using cerium and strontium and the assessment of its effect on microstructure and properties of the alloy. The addi- tion of cerium simultaneously modified both primary and eutectic silicon, leading to an increase in ultimate tensile strength, as well as the wear resistance of the alloy. It was found that the coefficient of thermal expan- sion of the alloy decreased on modification of the microstructure. KEYWORDS: Al-Si hypereutectic alloy, primary silicon, eutectic silicon, mechanical properties, coefficient of thermal expansion (CTE) Introduction Al-Si alloys are aluminum-base alloys with silicon as the major additive. They are among the most useful aluminum casting alloys because of their high fluidity, high resistance to corrosion, reduc- tion in shrinkage, low coefficient of thermal expansion, etc. They have a wide variety of applica- tions in automotive casting. These alloys usually contain about 2 % to 25 % of silicon, together with some amount of impurities of the order of 1.5 % to 2 %. The most widely used alloys are found in the range of 3 %–22 % of silicon. The additions, like copper, nickel, zinc, magnesium, and other alloying elements, are added depending upon the use of the alloy [1]. Based on the Si concentration in weight % (wt. %), the Al-Si alloy systems fall into three major categories: hypoeutectic (<12 % Si), eutectic (12 %–13 % Si), and hypereutectic (14 %–25 % Si). The addition of silicon to the aluminum alloy reduces the coefficient of thermal expansion and improves the wear resistance, as well as the fluidity, of the alloy [2]. Therefore, hypereutectic alloys with high silicon content are used for internal combustion engine parts, especially pistons. The other applications of hypereutectic Al-Si alloys include high-performance automobile engine parts, such as connecting rods, rocker arms, cylinder sleeves, and piston rings [3]. The cast microstructure of the hypereutectic Al-Si alloy generally consists of coarser and segre- gated primary silicon crystals and needle-like eutectic silicon. They greatly degrade the mechanical Manuscript received April 17, 2012; accepted for publication July 8, 2013; published online August 30, 2013. 1 Dept. of Metallurgical and Materials Engineering, National Institute of Technology, Karnataka, Surathkal, Srinivasnagar, Mangalore 575025, India. 2 Light Metals and Composites Division, National Institute for Interdisciplinary Science & Technology (CSIR), Trivandrum 695019, India, e-mail: manickravi@yahoo.com 3 Dept. of Metallurgical and Materials Engineering, National Institute of Technology, Karnataka, Surathkal, Srinivasnagar, Mangalore 575025, India, e-mail: prabhukn_2002@yahoo.co.in 296 Copyright V C 2013 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Materials Performance and Characterization, Vol. 2, No. 1 Paper ID MPC20120007 www.astm.org Copyright by ASTM Int'l (all rights reserved); Mon Jun 23 02:18:04 EDT 2014 Downloaded/printed by National Institute of Technology pursuant to License Agreement. No further reproductions authorized.