Effect of spark plasma sintering and high-pressure torsion on the microstructural and mechanical properties of a Cu–SiC composite

P Bazarnik,S Nosewicz,B Romelczyk-Baishya,M Chmielewski,A Strojny Nędza,J Maj,Y Huang,M Lewandowska,T.G Langdon

doi:10.1016/j.msea.2019.138350

Abstract

This investigation examines the problem of homogenization in metal matrix composites (MMCs) and the methods of increasing their strength using severe plastic deformation (SPD). In this research MMCs of pure copper and silicon carbide were synthesized by spark plasma sintering (SPS) and then further processed via high-pressure torsion (HPT). The microstructures in the sintered and in the deformed materials were investigated using Scanning Electron Microscopy (SEM) and Scanning Transmission Electron Microscopy (STEM). The mechanical properties were evaluated in microhardness tests and in tensile testing. The thermal conductivity of the composites was measured with the use of a laser pulse technique. Microstructural analysis revealed that HPT processing leads to an improved densification of the SPS-produced composites with significant grain refinement in the copper matrix and with fragmentation of the SiC particles and their homogeneous distribution in the copper matrix. The HPT processing of Cu and the Cu–SiC samples enhanced their mechanical properties at the expense of limiting their plasticity. Processing by HPT also had a major influence on the thermal conductivity of materials. It is demonstrated that the deformed samples exhibit higher thermal conductivity than the initial coarse-grained samples.

Highlights

Metal matrix composites (MMCs) are lightweight structural materials which often exhibit unique properties such as enhanced strength and hardness [1,2], wear [3] and corrosion resistance [4,5,6] together with excellent electrical and thermal properties [6,7,8]
Some residual porosity is visible in the copper matrix, as presented in Fig. 1b with high magnification where the black regions in the back-scattered electron (BSE) image are pores
The results clearly show that the high plastic deformation introduced during highpressure torsion (HPT) processing enhances the thermal conductivity

Summary

Introduction

Metal matrix composites (MMCs) are lightweight structural materials which often exhibit unique properties such as enhanced strength and hardness [1,2], wear [3] and corrosion resistance [4,5,6] together with excellent electrical and thermal properties [6,7,8]. Copper and its alloys exhibit excellent thermal and electrical conductive properties but, due to their poor mechanical properties of very low wear resistance and low yield strength, especially at elevated temperature, their use is restricted in many industrial applications. Cu-based MMCs reinforced with ceramic particles are under consideration as promising candidate materials for applications requiring high thermal conductivity and thermal stability together with excellent wear resistance. Cu–SiC composites have been used extensively as welding electrodes, electrical contacts, and switches and in electronic packaging [17]

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