Effect of the amount of cold working and ageing on the ductility of a Cu–15%Cr–0.2%Ti in-situ composite

An in-situ composite has been produced by using a process which combines casting, hot forging and cold drawing of a Cu–15wt%Cr–0.2wt%Ti alloy. The effect of the amount of cold working and ageing on the ductility of this composite has been studied by using a combination of tensile testing, microhardness testing and microstructural characterization. It has been observed that the elongation to fracture of the composite decreases significantly with increasing drawing strain and the decrease in ductility is closely associated with the increase in strength. This observation can be attributed to the work hardening of copper matrix and the decrease in inter-fibre spacing. Ageing for 1 h at 748 K increases the ductility without sacrificing the strength for the composite with a drawing strain in the range of 3–5.3. It is likely that the change of dominant hardening mechanism of the copper phase from work hardening to precipitation hardening is favourable to the ductility of the composite. In terms of the fracture mode of the composite under tensile loading, it is likely that the composite fails by first fracturing the chromium fibres to nucleate the microvoids and then rupturing the copper matrix.