Dry sliding wear behaviour of Al–12Si–4Mg alloy with cerium addition A.S. Anasyida a,b , A.R. Daud a, * , M.J. Ghazali c a School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia b School of Material Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Seberang Prai Selatan, Pulau Pinang, Malaysia c Department of Mechanical and Material Engineering, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia article info Article history: Received 29 March 2009 Accepted 7 June 2009 Available online 10 June 2009 Keywords: Aluminium alloy Casting Cerium Intermetallic Wear resistance Microhardness abstract The purpose of this work is to understand the effect of cerium addition on wear resistance behaviour of as-cast alloys. Al–12Si–4 Mg alloys with 1–5 wt% cerium addition were prepared using the casting tech- nique. A sliding wear test was carried out under applied loads of 10 N, 30 N and 50 N at a fixed sliding speed of 1 m/s using a pin-on-disc configuration. The wear test was conducted in dry conditions at room temperature of 25 °C. Detailed analysis of the microstructure, worn surface, collected debris and microhardness was undertaken in order to investigate the differences between the as-cast alloys with dif- ferent levels of cerium addition. The addition of 1–5 wt% cerium was found to lead to the precipitation of intermetallic phases (Al–Ce), resulting a needle-like structures. Increasing cerium content up to 2 wt% improved both wear resistance and microhardness of as-cast alloys. Addition of more than 2 wt% cerium, however, led to a decrease in microhardness, resulting in lower wear resistance of the alloys. Moderate wear was observed at all loads, with specific wear rates (K 0 ) ranging from 6.82  10 5 with 2 wt% Ce at applied load of 50 N to 21.48  10 5 mm 3 /N m without added Ce at an applied load of 10 N. Based on K 0 ranges, the as-cast alloys exhibited moderate wear regimes, and the mechanism of wear is a combina- tion of abrasion and adhesion. Alloy containing 2 wt% Ce, with the highest hardness and lowest K 0 value, showed the greatest wear resistance. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Aluminium–silicon (Al–Si) alloys are widely used as engineer- ing materials due to their light weight, ease of fabrication at a rea- sonable cost, high strength to weight ratio, excellent castability, corrosion resistance, good weldability, good thermal conductivity and wear resistance properties [1]. They are, therefore, well suited for application in aerospace, automobile, military and construction [2]. Since Al–Si alloys have been used for tribological applications like internal combustion engines, pistons, liners, clutches, pulleys, rockers and pivots [3], it is becoming increasingly important to study the tribological behaviour of aluminium-based materials and to seek techniques to improve the wear properties of these al- loys. On-going research has sought to enhance the mechanical and wear resistance properties of Al–Si alloys by controlling their microstructures via suitable casting procedures [4], heat treatment [5,6] or addition of minor alloying elements [7,8]. The addition of alloying elements has been found to be the easiest and most effi- cient method to improve the mechanical properties of the alloys [9]. Among the alloying elements, rare earth has many positive ef- fects on high strength aluminium cast alloys. Rare earth elements refine grain sizes, modify eutectic microstructures, improve distri- bution of the inclusion phases and reduce the contents of gases and some impurities as well as the spacing between secondary den- drite arms. Rare earth elements also have a strong chemical appe- tency with hydrogen and oxygen elements, which helps to reduce the hydrogen and oxygen contents. Blowholes and pinholes which form during the solidification process of the aluminium liquid can also be eliminated. Thus, a compactable casting can be achieved with rare earth elements. Besides that, rare earth elements like cer- ium (Ce) can also increase heat resistance properties and reduce the linear expansion coefficient of aluminium alloys [10]. Addition of Ce as a micro-alloying element in aluminium alloys has been found to form a number of intermetallic compounds with alumin- ium and silicon such as Al 4 Ce, Al 2 Ce, SiCe and SiCe 4 [11]. The addition of alloying elements can influence the wear prop- erties of Al–Si alloys due to solid solution strengthening and pre- cipitation hardening. Saheb et al. [12] have reported that the addition of titanium (Ti) to binary Al–Si alloy improved the wear resistance of both as-cast and heat-treated alloys due to the precip- itation of the Al 3 Ti phase. However, these alloys displayed higher wear rates, thus lower wear resistance, compared to the Al–Si bin- ary alloy. The addition of Cu (3–5 wt%) to hypereutectic Al–Si alloy also improved wear resistance at high loads due to the precipita- tion of a hard-phased Al 2 Cu [13]. Harun et al. [11] reported that the addition of cerium, zinc, and zirconium with subsequent heat 0261-3069/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2009.06.007 * Corresponding author. Tel.: +603 89213806; fax: +603 89213777. E-mail address: ard@ukm.my (A.R. Daud). Materials and Design 31 (2010) 365–374 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes