Stability of the metastable β'-Cu4Ti phase in Cu[sbnd]Ti alloys: Role of the Ti content

Abstract

The stability of the metastable β'-Cu4Ti phase is a crucial factor for the electrical conductivity of CuTi alloys. Determining the factors that influence the stability of the β'-Cu4Ti phase and the relationship between the β'-Cu4Ti phase and the electrical conductivity of CuTi alloys is a prerequisite to improve their electrical conductivity. In this study, the stabilities of the β'-Cu4Ti and β-Cu4Ti phases were investigated by first-principles calculations combined with experimental characterization. When the Ti content of the β'-Cu4Ti phase is greater than or equal to 19 at.%, its stability is lower than that of the β-Cu4Ti phase, resulting in instability of the β'-Cu4Ti phase and dissolution of Ti atoms back into the Cu matrix. This is the main reason why it is difficult to improve the electrical conductivity of CuTi alloys when the β'-Cu4Ti phase is the main strengthening precipitate.