Improved mechanical properties of magnesium–graphene composites with copper–graphene hybrids M. Rashad* 1,2 , F. Pan 1,2,3 , M. Asif 4 and A. Ullah 5 New magnesium nanocomposites reinforced with copper–graphene nanoplatelet hybrid particles have been prepared through semipowder metallurgy method. Compared with monolithic Mg, the Mg–1Cu–xGNPs nanocomposites exhibited higher tensile and compressive strength. In tension, nanocomposites revealed substantial enhancement in elastic modulus, 0?2% yield strength, ultimate tensile strength and failure strain (up to z89, z117, z58 and z96% respectively) compared to monolithic Mg. In compression, nanocomposites showed best improvement in 0?2% yield strength, and ultimate compressive strength and failure strain (%) (up to z34, z59 and z61% respectively), while compressive elastic modulus first increases and then decreases with increase in graphene nanoplatelets (GNPs) contents. Enhanced strength of composites can be attributed to basic strengthening mechanisms that might be accountable, owing to addition of Cu–GNPs hybrids. Keywords: Powder metallurgy method, Mechanical properties, Metal matrix composite Introduction Owing to low density, high specific strength, good machinability and easy recycling, magnesium and its alloys have widespread applications in the fields of automobile, aerospace and electronic industries. However, the usage of magnesium is limited due to its low strength and ductility, as compared to steel and aluminium. Mechanical properties of magnesium can be enhanced by incorporation of temperature stable rein- forcement in the magnesium matrix. Since Mg compo- sites have several advantages compared to monolithic Mg, numerous studies have been conducted on Mg based composites. Literature reviews revealed that Y 2 O 3 , Al 2 O 3 , SiC, Ti, TiC and carbon nanotube (CNT) 1–8 have been extensively used to enhance the mechanical properties of the monolithic Mg. Recently, several attempts have been made to enhance the mechanical strength of Mg using hybrid reinforcements, i.e. ceramiczmetal, ceramiczceramic, metalzCNTs, etc. 9–12 Previous studies showed that both strength and ductility of pure Mg can be improved with addition of hybrid reinforcement. Reinforcements used in the composites are normally in the form of powders. Therefore, a number of researchers have used the powder metallurgy technique for fabricating magnesium based composites. Powder metallurgy is an advanced metal forming technology used for producing high quality structural components with near net shape. Main advantage of powder metallurgy method is that all kinds of materials can be mixed to fabricate the composites. However, Mg based composites are difficult to fabricate through powder metallurgy method because during ball milling, Mg powder can burn easily due to heat production. Therefore, semipowder metallurgy method is proposed here to fabricate the Mg based composites. Composite powders are mixed in a solvent (ethanol) using a mechanical agitator instead of ball milling. After filtration and vacuum drying, composite powders can be processed for cold pressing, sintering and hot extrusion. Graphene, a single atomic layer of sp 2 hybridised carbon, has attracted significant attention owing to its fascinating electrical, thermal and mechanical properties. The modulus of elasticity and intrinsic fracture streng- th of monolayer graphene are 1 TPa and 125 GPa respectively. 13–15 Its mechanical properties are compar- able to CNTs (modulus of elasticity up to 0?9 TPa; fracture strength up to 150 GPa). 16 In the past few years, researches have made successful attempts for graphene oxide and graphene–polymer composites similar to CNT based polymer composites. 17–19 However, the Mg com- posites reinforced with graphene particles are limited in the literature. 20,21 No attempt has been made so far to fabricate the Mg composites reinforced with hybrid Cu– graphene nanoplatelets (GNPs) nanoparticles. 1 College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China 2 National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China 3 Chongqing Academy of Science and Technology, Chongqing, Chongqing 401123, China 4 School of Materials Science and Engineering, Dalian University of Technology, Dalian116024, China 5 Department of Physics, Quaid-i-Azam University, Islamabad 46000, Pakistan *Corresponding author: email rashadphy87@gmail.com ß 2014 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute Received 4 September 2014; accepted 18 November 2014 DOI 10.1179/1743284714Y.0000000726 Materials Science and Technology 2014 VOL 000 NO 000 1