Thermophysical properties of a Cu–Ti–C–B SHS composite

Abstract

The paper studies the thermophysical properties of a Cu-Ti-C-B composite produced by self-propagating high-temperature synthesis (SHS) of an initial mixture of copper, titanium, boron carbide (B4C), and carbon powders. The matrix of the composite is a supersaturated solid solution of titanium in a copper lattice with Cu4Ti nanosized particles homogeneously precipitated under cooling. The matrix microhardness is 450 HV 0.1. Particles of titanium carbide (TiC) and titanium diboride (TiB2) resulting from SHS are randomly distributed in the bulk of the composite. The microhardness of the regions with the predominance of TiC particles is 640 HV 0.1, and the microhardness of the regions with the predominance of TiB2 particles is 900 HV 0.1. The average hardness of the composite is 60 HRC. Differential scanning calorimetry demonstrates a unified wide exothermic effect at temperatures ranging from 750 to 1000 °С, with an enthalpy of 148.6 J/g, associated with the exothermic reaction between residual titanium and boron carbide (B4C), which did not react during SHS. The temperature dependences of density, thermal diffusivity, heat capacity, thermal conductivity, and the coefficient of linear thermal expansion are experimentally determined. The particles of the strengthening phases are found to reduce slightly the thermal properties of the composite compared to pure copper. It is shown that annealing at temperatures of 800 and 860°C decreases the level of residual stresses in the composite matrix.