A new ultrahigh strength Cu–Ni–Si alloy

A new ultrahigh strength Cu-6.0 Ni-1.0 Si-0.5 Al-0.15 Mg-0.1 Cr alloy has been developed by alloying design and thermal mechanical treatment. Electrical conductivity, mechanical properties of the designed alloy such as hardness, tensile strength, yield strength, elongation and anti-stress relaxation resistance were tested. The mechanical properties and electrical properties of designed alloy were comparable to those of Cu–Be alloys, and its anti-stress relaxation resistance even was better than that of Cu–Be alloys at evaluated temperature. Microstructure observation revealed that β-Ni3Si phase precipitated in the initial stages ageing process, with further increasing the ageing time, β-Ni3Si, and δ-Ni2Si phase precipitates appeared and contributed to the ultrahigh strength by Orowan strengthening. The satellites spots around diffraction spots of Cu matrix symmetrically in [112]Cu zone crystal axis have been determined, resulting that satellites spots are from the electron diffraction of δ-Ni2Si precipitates. The crystal orientation relationship between matrix and precipitates is that: ( 11 1 ¯ ) cu / / ( 11 1 ¯ ) β / / ( 0 2 ¯ 1 ) δ ; [ 112 ] cu / / [ 112 ] β / / [ 012 ] δ .