Mechanical properties and electrical conductivity of Cu–Cr and Cu–Cr–4% SiC nanocomposites for thermo-electric applications

The present work investigates the feasibility of microwave sintering to produce bulk metal-based nanocomposites having blend composition of Cu99Cr1, Cu94Cr6, Cu99Cr1–4 wt.% SiC and Cu94Cr6–4 wt.% SiC (average particle size ∼30 nm). The 50 h ball-milled samples were uniaxially pressed, and then pellets were sintered at 800 °C, 900 °C and 1000 °C for a constant soaking period of 30 min by microwave sintering technique. Microstructural characterization was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Sintered compacts resulted a highly densified compacts (∼95% relative density) while retaining ultra-fine grains (100–200 nm) in the matrix. The mechanical properties, namely, hardness and wear resistance, and electrical conductivity of the sintered specimens were also evaluated. The best combination of mechanical properties (e.g. hardness ∼2.4 GPa) and electrical conductivity (60.3% of IACS) were obtained for Cu94Cr6–4 wt.% SiC sintered at 900 °C. This is possibly due to presence of ultra-fine grains in the bulk samples, good densification and proper bonding between particles. The results were analyzed in the light of interactions of microwaves between metallic matrix and microwave susceptive SiC particulates.

► Ball-milled Cu–Cr and Cu–Cr–SiC nanopowders successfully consolidated by microwave sintering. ► Addition of nanosize SiC in Cu–Cr leads to enhanced sintered density, wear and hardness. ► A good combination of wear resistance, hardness and electrical conductivity resulted in Cu94Cr6–4% SiC. ► Microwave suscepting SiC particles played a pivotal role in good densification retaining matrix grains <200 nm.