Microstructural evolution and properties of the aged Cu-3Ti-3Ni alloy

Abstract:

The effect of aging treatment on the microstructure and properties of Cu-3Ti-3Ni alloy was studied. The microstructure and precipitated phase were characterized by X-ray diffractometer, scanning electron microscope and transmission electron microscope, and the hardness, electrical conductivity and elastic modulus were measured as well. The results show that a number of Ni3Ti and β'-Cu4Ti phase precipitate from the Cu matrix after aging treatment. With increase of secondary aging time, the partial alloying elements dissolve into the Cu matrix and the metastable Cu4Ti phase transform into incoherent equilibrium Cu3Ti phase. The enhanced electrical conductivity is ascribed to the decrease of Ti solubility in the Cu matrix by the formation of the Ni3Ti and β'-Cu4Ti precipitates. After an appropriate aging treatment of Cu-3Ti-3Ni alloy, the Ni3Ti and coherent metastable β'-Cu4Ti phase 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 range of the experiments, the optimal two-step aging treatment for Cu-3Ti-3Ni alloy is at 300°C for 2 h and 450 °C for 7 h. The hardness, electrical conductivity and elastic modulus are 183 HV, 31.34 %IACS (International Annealed Copper Standard) and 148.62 GPa, respectively.