Stability of the metastable '-Cu4Ti phase in Cu-Ti alloys: Role of the Ti content

The stability of the metastable & beta;'-Cu4Ti phase is a crucial factor for the electrical conductivity of Cu-Ti alloys. Determining the factors that influence the stability of the & beta;'-Cu4Ti phase and the relationship between the & beta;'-Cu4Ti phase and the electrical conductivity of Cu-Ti alloys is a prerequisite to improve their electrical con-ductivity. In this study, the stabilities of the & beta;'-Cu4Ti and & beta;-Cu4Ti phases were investigated by first-principles calculations combined with experimental characterization. When the Ti content of the & beta;'-Cu4Ti phase is greater than or equal to 19 at.%, its stability is lower than that of the & beta;-Cu4Ti phase, resulting in instability of the & beta;'-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 Cu-Ti alloys when the & beta;'-Cu4Ti phase is the main strengthening precipitate.