Effects of sintering temperature and graphite addition on the mechanical properties of aluminum F.H. Latief a , El-Sayed M. Sherif a,b, * a Center of Excellence for Research in Engineering Materials (CEREM), Advanced Manufacturing Institute, King Saud University, P. O. Box 800, Riyadh 11421, Saudi Arabia b Electrochemistry and Corrosion Laboratory, Department of Physical Chemistry, National Research Centre (NRC), Dokki, 12622 Cairo, Egypt 1. Introduction Aluminum and its alloys are widely used in many industrial applications owing to their important characteristics. They are characterized by their good electrical and thermal conductivities, high strength to weight ratio, easy to deform, high ductility, good workability, and good corrosion resistance [1–5]. Therefore aluminum alloys have been used as a material in manufacturing automobile and aircraft components due to their high strength to weight ratio in order to make the moving vehicle lighter, which results in saving in fuel consumption, household appliances, aviation, containers, etc. [5–9]. The powder metallurgy (P/M) technique can be used in fabricating different alloys in the solid state including aluminum alloys. P/M has great versatility and low cost of production besides it is highly evolved method of manufacturing reliable net shaped components by blending elementalor pre-alloyed powders together. The P/M fabrication takes place by mixing the hardening particles with the metallic powders followed by consolidation and sintering [9–14]. The way of mixing raw materials controls both the distribution of particles and porosity of the alloy matrix. The distribution of particles and porosity of the alloy affect the mechanical properties as well as the tribological behavior of the fabricated alloys [13,14]. It has been reported that [14–17] the mechanical properties of an alloy depends mainly on the size of particles, i.e. increased mechanical properties will be obtained by using very fine particles and vice versa. However, the efficiency by which reinforcement particles strengthen the matrix depends on their type, size, morphology, volume fraction and overall distribution [18]. Exfoliated graphite nanoplatelets (xGnP) have attracted the attention as a substitute for carbon nanotubes, given the predicted excellent mechanical, structural, thermal and electrical properties of graphite and their similar properties to nanoscale carbon black and carbon nanotubes [19,20]. It is proven that the structure of graphite and carbon nanotubes are made up of the same building blocks [21]. Biswas and Drzal [22] have developed a process that can produce exfoliated graphite nanoplatelets of 4–10 nm in thickness and from 1 to 15 mm in diameter. The objective of our current work was to fabricate different aluminum-graphite alloys using the PM technique. The work has led to fabrication of three alloys, namely, Al-1 wt.%xGnP, Al-3 wt.%xGnP, and Al-5 wt.%xGnP, in addition to the pure aluminum, Al-0 wt.%xGnP. The objective was extended to report the effect of sintering temperature and the percentage of graphite additions on the density, microstruc- ture, compression strength and micro-hardness of aluminum. 2. Experimental 2.1. Materials An aluminum powder with 99.0% purity was supplied by Riedel-De Haen Ag Seelze-Hannover, Germany. The exfoliated graphite nanoplatelets particles were supplied by Asbury Graphite Mills, USA, with label of Asbury 3772. Journal of Industrial and Engineering Chemistry 18 (2012) 2129–2134 A R T I C L E I N F O Article history: Received 4 March 2012 Accepted 12 June 2012 Available online 19 June 2012 Keywords: Aluminum alloys Exfoliated graphite Mechanical properties Nanoparticles Sintering temperature A B S T R A C T The effects of different sintering temperatures, namely 400, 500 and 600 8C, on the mechanical properties of four aluminum–graphite alloys were reported. Different percentages of exfoliated graphite nanoplatelets particles (xGnP) were added to pure aluminum by using the powder metallurgy technique to produce Al-0 wt.%xGnP, Al-1 wt.%xGnP, Al-3 wt.%xGnP, and Al-5 wt.%xGnP. The density, fracture surface, compression, and hardness measurements were carried out to report the mechanical properties of the different aluminum–xGnP alloys. Combined data indicated that the Vickers hardness and compressive strength increase, on the other hand, the density decreases with increasing the graphite content in the Al alloys. ß 2012 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +966 14678938; fax: +966 14670199. E-mail address: esherif@ksu.edu.sa (E.M. Sherif). Contents lists available at SciVerse ScienceDirect Journal of Industrial and Engineering Chemistry jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jiec 1226-086X/$ – see front matter ß 2012 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jiec.2012.06.007