Effect of Reinforcement Content and Technological Parameters on the Properties of Cu-4 wt.% Ni-TiC Composites Pushkar Jha, R.K. Gautam, and Rajnesh Tyagi (Submitted December 31, 2016; in revised form July 2, 2017; published online September 25, 2017) The present study deals with the synthesis and investigation of microstructure, density, and hardness behavior of Cu-4 wt.% Ni-TiC metal matrix composites, produced by high-energy ball milling, followed by compaction and sintering. Matrix of Cu-4 wt.% Ni was used, and different weight percentages (0, 2, 4, 6, and 8) of TiC particles were added. The uniform distribution of TiC particles in the matrix alloy was confirmed by characterizing these composite powders by using scanning electron microscope, energy- dispersive spectroscopy, and x-ray diffraction. Both the density and the hardness of the composite con- taining 4 wt.% TiC were found to be the highest. The density was found to decrease with increasing TiC content beyond 4 wt.%, and it has been attributed to the agglomeration of TiC particles leading to the formation of pores when added in relatively larger amounts. The compressibility behaviors of the milled powders were studied by using Panelli and Ambrosio Filho equation. Keywords compressibility, metal matrix composites, micro-hardness, SEM, TiC particles, XRD 1. Introduction The current time is witnessing a high demand for advanced materials that reveal higher strength and better electrical as well as thermal conductivity. On account of having a very high electrical conductivity, thermal conductivity, ductility, and ease of forming, copper lends itself to countless applications, such as automobile radiators, heat sink materials, rocket nozzles, electrodes for resistance welding, and electric switches (Ref 1-4). However, the application scope of copper and its alloys becomes restricted due to its inferior mechanical properties at elevated temperatures. To achieve better mechanical strength, hardness, wear resistance, creep, and fatigue, ceramic particles- reinforced copper-based metal matrix composites are produced. These composites can be developed by various processes, such as powder metallurgy, squeeze casting, compocasting, and stir casting (Ref 5). Among these processes, powder metallurgy (P/ M) method is considered to be the most viable due to advantages such as restricting the unfavorable reaction among the matrix and reinforcement, chances of addition of more volume fraction of reinforcement, and uniform distribution of reinforced particles (Ref 6, 7). Powder metallurgy-processed microcomposites can reveal better properties, provided that the reinforcement particulates are dispersed homogeneously in the matrix. If the reinforcement is not properly distributed, the agglomeration of the reinforced particles occurs and that decreases the mechanical properties of the microcomposites (Ref 8). For preventing the agglomeration of the reinforcement particles in the matrix, particularly when the reinforcement particulates are smaller in size, mechanical alloying (MA) method is used for the homogeneous distribution of the reinforcement particles. The high-energy ball milling method is used for the production of composite metal powders with a fine microstructure. The procedure of mechanical alloying (MA) involves a repeated deformation, cold welding, and fracture of powder using high-energy ball milling. During high- energy ball milling, mechanical alloying imparts very high strain on the material by shear and fracture of phases. It results in structural refinement coupled with the recrystallization in the material. Various parameters influence the stages of milling, such as the ball-to-powder ratio (BPR), speed, temperature, milling atmosphere, process control agent, volume fraction, particles size, and type of reinforcement (Ref 9, 10). Various authors have effectively explored and reported the reinforcement by the ceramic particles, e.g., SiC, Fe 3 Al, graphite, WC, TiB 2 , Al 2 O 3 , and AlN in copper-based metal matrix composites, fabricated by mechanical alloying method (Ref 11-17). The TiC ceramic particles, as reinforcement in copper alloys, have attained little attention despite possessing high hardness, high chemical stability, high modulus, grain refining effect, better corrosion, and wear resistance (Ref 18). Compaction of the powder is performed to enhance the densification of the powder particles, having different geome- tries, at low cost and with high productivity. The compacted powders are then subjected to consolidation by sintering or hot pressing (Ref 19). Due to the significance of this process, several equations have been proposed for modeling the relationship between the powder density and porosity with the applied pressure (Ref 20-22). A critical review of above-mentioned literature makes it evident that few authors have worked on the titanium carbide particles-reinforced copper matrix composites and studied their Pushkar Jha, R.K. Gautam, and Rajnesh Tyagi, Department of Mechanical Engineering, Indian Institute of Technology, Banaras Hindu University, Varanasi 221005, India. Contact e-mail: pushkar.mec.iitbhu@gmail.com. JMEPEG (2017) 26:5126–5136 ÓASM International DOI: 10.1007/s11665-017-2939-5 1059-9495/$19.00 5126—Volume 26(10) October 2017 Journal of Materials Engineering and Performance