Study on discontinuous precipitation behaviour and performance change of Cu–Ti–Ni during aging

Abstract

ABSTRACT The discontinuous precipitation behaviour and properties of Cu–Ti–Ni alloy during aging precipitation were studied by means of electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that β'-Cu4Ti was formed in the matrix during the aging process of Cu–4Ti–1Ni alloy, and the cellular structure grows at the grain boundary in the form of discontinuous precipitation in the middle and late stages of aging, and expands to the interior of the grains with the aging time until the grains were completely covered, then a uniform Cu3Ti structure was formed. In addition, the coverage area of cellular tissue increases with aging time and temperature. Under different aging temperature conditions, the hardness of the alloy increases first and then decreases with the aging time, with a peak value of 319.8 HV and a strength of 782.2 MPa. The electrical conductivity increases rapidly and then increases slowly with aging time, reaching 15.5 IACS after aging at 500°C for 10 h. Based on the Avrami equation, the kinetic analysis of discontinuous precipitation at different temperatures was established.