Trans. Nonferrous Met. Soc. China 28(2018) 1705−1713 Improvement in dry sliding wear resistance of Al−17Si−5Cu alloy after an enhanced heat treatment process Biplab HAZRA, Pankaj BARANWAL, Supriya BERA, Bijay Kumar SHOW Department of Metallurgical and Materials Engineering, National Institute of Technology Durgapur, West Bengal, 713209, India Received 9 November 2017; accepted 3 February 2018 Abstract: To improve the wear resistance of cast Al−17Si−5Cu alloy (AR alloy), isothermal heat treatment is employed to modify the morphology of Si particles (particularly eutectic Si particles). Furthermore, wear behaviour of heat-treated alloy (HT alloy) along with AR alloy is studied using a pin-on-disc tribometer. Worn surfaces are then characterised using scanning electron microscope. The result reveals considerable microstructural modifications after the heat treatment. Accordingly, higher hardness value in HT alloy is obtained compared with AR alloy. The overall wear rate for HT alloy is found to be significantly lower compared with AR alloy at all the applied loads, indicating remarkable improvement in wear resistance. Eutectic Si particles become from acicular/rod-like to spherical/equiaxed morphology (aspect ratio close to 1) on heat treatment, resulting in good bonding with the matrix. Thus, they remain intact during wear and being harder, providing resistance to wear. Moreover, the increased hardness on heat treatment causes further resistance to wear. Therefore, the combined effect of intact harder Si particles on the wearing surface and higher hardness results in superior wear behavior in HT alloy at all loads compared with AR alloy. Key words: heat treatment; abrasive wear; hypereutectic Al−Si alloys 1 Introduction Cast Al−Si alloys have widespread applications in various important components for automobile sector due to their excellent combination of properties [1]. Among various Al casting alloys, Al−Si alloys are being used extensively, particularly in the transportation industry [2]. However, in recent years, hypereutectic Al−Si alloy has become an attractive area of research due to its potential to replace cast iron parts in automobile applications [1]. The morphology, size and distribution of primary as well as eutectic silicon crystals in these alloys greatly affect their properties. Both refinement and modification of primary and eutectic silicon and controlling the solidification parameters are reported to enhance the mechanical properties of hypereutectic Al−Si alloy [1]. On the other hand, tribological properties of cast hypereutectic Al−Si alloys need to be investigated for successful application of these alloys as engine block materials. Like mechanical properties, wear behavior is also greatly dependent on size, shape and amount of different microstructural constituents. HU et al [3] reported improved wear resistance in Al−16Si− 4Cu−0.5Mg alloy after microstructural modifications. Wear studies on Al−Si alloys with varying Si content and other alloying elements under dry sliding conditions have been studied for many years [4,5]. These studies used various test configurations under various loads and sliding speeds. However, detailed evaluation of wear behavior and the mechanisms of wear are limited. Among different Al−Si alloys, hypereutectic Al−Si alloys are found to have applications in engine components owing to their good resistance to wear. Al−Si alloys, used as an engine block material in the linerless Chevrolet Vega 2300 engine, was a hypereutectic A390 alloy which was first introduced at the AFS Casting Congress [6]. After successful use in the Vega, A390 alloy was later used in Chevrolet Corvette ZL1, Porsche 928, Mercedes 3.8L V8, and other engines [7]. However, their application has been restricted to luxurious vehicles only due to higher production cost. Improved wear properties in these Al−Si alloys are achieved primarily because of the presence of harder silicon particles in the aluminum matrix. It has been reported [8] that, not only strength but also wear Corresponding author: Bijay Kumar SHOW; Tel: +91-343-2754739; Fax: +91-343-2547375; E-mail: bijayshow@gmail.com DOI: 10.1016/S1003-6326(18)64814-9