Microstructural Evolution and Properties of Aged Cu-3Ti-3Ni Alloy

Abstract

The effect of aging treatment on the microstructure and the properties of Cu-3Ti-3Ni alloy was studied. The microstructure and the precipitated phase were characterized by X-ray diffractometer, scanning electron microscope and transmission electron microscope, and hardness, electrical conductivity and elastic modulus were measured as well. The results show that a number of Ni 3 Ti and β′ -Cu 4 Ti phases precipitate from the Cu matrix after aging treatment. With the increase of secondary aging time, partial alloying elements dissolve into the Cu matrix, and the metastable Cu 4 Ti phase transforms into incoherent equilibrium Cu 3 Ti phase. The enhanced electrical conductivity is ascribed to the decrease of Ti solubility in the Cu matrix by the formation of the Ni 3 Ti and β′ -Cu 4 Ti precipitates. After an appropriate aging treatment of Cu-3Ti-3Ni alloy, the Ni 3 Ti and coherent metastable β′ -Cu 4 Ti phases precipitate completely, giving rise to the increase of hardness. Aging treatment has no obvious effect on the elastic modulus of Cu-3Ti-3Ni alloy. In the scope of the experiments, the optimal two-step aging treatment parameter for Cu-3Ti-3Ni alloy is to age at 300 °C for 2 h followed by aging at 450 °C for 7 h. The HV hardness, the electrical conductivity and elastic modulus are 1.83 GPa, 31.34 %IACS (International Annealed Copper Standard) and 148.62 GPa, respectively.