Mechanical and electrical properties of copper-graphene nanocomposite fabricated by high pressure torsion Nidhi Khobragade a , Koushik Sikdar a , Binod Kumar a , Supriya Bera b , Debdas Roy a, * a Department of Materials and Metallurgical Engineering, NIFFT, Ranchi-834003, Jharkhand, India b Department of Materials and Metallurgical Engineering, NIT, Durgapur -713209, WB, India article info Article history: Received 8 August 2018 Received in revised form 11 October 2018 Accepted 12 October 2018 Available online 19 October 2018 Keywords: High pressure torsion Copper Graphene Dislocations Hardness Electrical conductivity abstract Graphene reinforced Cu matrix composite was fabricated by consolidating mechanically mixed powder blend to 98% theoretical density by High Pressure Torsion (HPT). Microstructural characterization by scanning electron microscopy (SEM) elicits even distribution of the reinforcement phase into the matrix. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirms nanocrystalline micro- structure and strong interfacial bonding between Cu and graphene. Addition of 10 wt % graphene yields maximum hardness (~2.67 GPa) and Young's modulus (~102.03 GPa). The increment in strength was attributed to the microstructural refinement and dislocation pinning at the strong matrix-reinforcement interface. The electrical conductivity of the Cu- 10 wt% graphene composite was found to be ~87% IACS. Results indicated that HPT consolidation is an efficient mean for synthesizing Cu-graphene composite with improved strength (~2 times higher hardness than pure Cu processed under similar condition) with negotiable conductivity. © 2018 Published by Elsevier B.V. 1. Introduction Unique property combination of the Metal matrix composites (MMC's) containing low dimensional reinforcement phase has to intrigue its development for practical engineering applications [1e3]. Performance of the composite is mainly dictated by the property, volume fraction and the distribution of the reinforcement phase into the matrix. CNT (1-D) is a carbon allotrope; have very high tensile strength (~100 GPa), Young's modulus (~1 TPa), excel- lent thermal and/or electrical conductivity (Thermal conductivity 5:3  10 3 Wm 1 K 1 ), electrical conductivity (5  10 8  6  10 2 U m) with very low density (1:06 g=cc) [4e8]. Cu is a commonly used material for electrical and/or thermal conductor owing to its low intrinsic resistivity. Therefore, the development of Cu-based MMC's by incorporating low dimensional carbon allo- tropes have drawn attention especially for applications like elec- trode, heat sink, integrated circuits and chips [9e11]. Existing literature suggests that despite the rigorous effort, extensive development of CNT reinforced MMC's were restricted mainly by its production cost, agglomeration, damage, inferior interfacial bonding with the matrix phase and requirement of cumbersome processing routes [12, 13]. Graphene (2-D) is a sp 2 hybridized carbon allotrope arranged in 2-D lattice; developed by Novoselov and Geim in 2004 [14]. It has a large theoretical specific surface area (2630 m 2 g 1 ), high intrinsic mobility ð200000 cm 2 v 1 s 1 Þ, Young's modulus ð 1:0 TPa), ther- mal conductivity ð 5000 Wm 1 K 1 Þ and electrical conductivity 10 6 S m-1 [15e20]. Investigation suggests that graphene is cheaper than CNT and can be produced industrially in large scale [21 ,22]. Additionally, the 2-D structure provides an ease over 1D CNT for its dispersion into the metallic matrix [23,24]. Hence, the economic viability, unique property combinations and technical preeminence garnered attention for the development of graphene based MMC's especially as a potential replacement of the CNT based one. The major challenge of developing graphene reinforced MMC is its homogeneous dispersion and inferior interfacial bonding [25e27]. Ball milling is an efficient means for dispersing graphene into the metallic matrix, therefore, most of the graphene reinforced MMC's are fabricated by using the powder metallurgy route i.e. mechanical mixing of powders followed by its consolidation [28e31]. Yang et al. [1] prepared graphene nano-ribbon (GNR) reinforced Cu matrix composite by spark plasma sintering (SPS, 600  C) of * Corresponding author. E-mail addresses: koushik2k16@gmail.com (K. Sikdar), droy2k6@gmail.com (D. Roy). Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom https://doi.org/10.1016/j.jallcom.2018.10.139 0925-8388/© 2018 Published by Elsevier B.V. Journal of Alloys and Compounds 776 (2019) 123e132