TECHNICAL PAPER Effect of Aging Time on Mechanical Properties and Wear Characteristics of Near Eutectic Al–Si–Cu–Mg–Ni Piston Alloy Pratheesh Krishnankutty 1 • Allesu Kanjirathinkal 1 • M. A. Joseph 1 • M. Ravi 2 Received: 15 April 2015 / Accepted: 18 May 2015 / Published online: 13 June 2015 Ó The Indian Institute of Metals - IIM 2015 Abstract Al–12Si–3Cu–1 Mg–1.78Ni alloy is widely used for piston parts in automobile industry. The present paper investigates the effect of aging time for 1–16 h at 180 °C after solution treatment of the alloy at 500 °C for 5 h, on alloys prepared by gravity casting and squeeze casting. The wear rate of the alloy shows a minimum at an intermediate aging time. The hardness and ultimate tensile strength showed a peak at intermediate aging time. Mechanical properties and wear resistance are found to be better in squeeze cast alloy. The result are explained based on the microstructure developed during casting process and on heat treatment for various durations. Keywords Aluminium alloys  Die casting  Mechanical properties  Electron microscopy  Wear resistance 1 Introduction The automobile industry is increasingly using aluminium– silicon alloys cast at near eutectic and aging-hardened due to their good wear resistance, low thermal expansion, rel- atively high specific strength at low specific weight and low cost, resulting in affordable improvements in fuel efficiency. By heat treatment, the microstructure of near eutectic aluminium silicon alloys can be modified and its properties improved [1]. Factors like the temperature and aging time affect not only the as-cast microstructure but also the mechanical properties and wear characteristics of heat treated Al–Si alloys [2, 3]. Copper is added for arresting natural aging but increases the kinetics of artifi- cial aging. Nickel and magnesium are added to increase the strength [4]. An improvement in wear resistance of 390 Al alloys after heat treatment was observed. Yasmin et al. [5] studied the mechanical and wear properties of Al–Si eutectic alloy and found that full heat treatment has a great influence on the wear and mechanical properties of the Al– Si piston alloy. Haque and Sharif [6] also noted that heat treatment show a great influence on the mechanical and wear properties of the Al–Si piston alloy as it reduces the wear rate and increases the ultimate tensile strength. Modern casting processes like squeeze casting are used to cast Al–Si alloys to overcome the disadvantages of the conventional die-casting process [7]. In the present study influence of aging time on mechanical and wear properties of cast Al–Si–Cu–Mg–Ni piston alloy has been investi- gated. The study also aims to understand the effect of heat treatment on the mechanical and wear properties of both as cast and squeeze cast Al–Si–Cu–Mg–Ni piston alloy. 2 Experimental Procedure 2.1 Preparation of Castings The experimental alloys are prepared using as received LM6 alloy ingots, Al–30 % Cu master alloy, Al–20 %Mg master alloy and Al–75 %Ni master alloy. The LM6 alloys are melted in graphite crucibles in an electrical resistance pit furnace at 800 °C. After the alloy melted completely, & Pratheesh Krishnankutty krishnankuttyp1979@gmail.com 1 Department of Mechanical Engineering, National Institute of Technology, Calicut 673601, Kerala, India 2 National Institute for Interdisciplinary Science and Technology (CSIR), Thiruvananthapuram 695019, Kerala, India 123 Trans Indian Inst Met (2015) 68(Suppl 1):S25–S30 DOI 10.1007/s12666-015-0584-y