Effect of cold-working and aging processes on the microstructure, mechanical properties and electrical conductivity of Cu–13.5%Mn–4%Ni–1.2%Ti alloy

In this study, variations of hardness, electrical conductivity, strength, elongation and microstructure of the Cu–13.5%Mn–4%Ni–1.2%Ti alloy were investigated during aging, cold-working and subsequent aging. X-ray diffraction (XRD), transmission electron microscopy and scanning electron microscopy methods were used to evaluate the microstructure of the alloy. Tensile, hardness and electrical conductivity measurements were also used for investigating the effects of processing parameters on the characteristic of the alloy. Hardness value of 190 HV and strength of 644 MPa were obtained after aging the as-cast alloy for 4 h at the temperature of 500 °C. The maximum hardness and strength increased up to 253 HV and 816 MPa, respectively, after aging 60% cold-worked samples for 1 h at the temperature of 500 °C. The dominant strengthening mechanism during aging was attributed to the precipitation of Cu4Ti phase. Formation of the β-Cu3Ti phase during aging at the temperature of 500 °C was another reason of strengthening. As a result of aging, electrical conductivity of both as-cast and cold-worked alloys was improved. The maximum conductivity of 29.7% IACS was attained after aging the as-cast material at the temperature of 500 °C for 4 h.

► Mn2Ti4O precipitates observed in the microstructure of as-cast alloys.
► During aging at 400, 450 and 500 °C hardness reached the value of 139, 165 and 192 HV.
► β-Cu3Ti and Ni3Ti precipitates formed during over aging at temperatures of 500 °C.
► Electrical conductivity was 29.7% IACS in the 0% cold worked samples aged at 500 °C.
► Conductivity of 28% IACS, hardness of 250 HV obtained by 60% cold work + aging at 450 °C.