Compositions with tie-lines between the σ and (γ, δ) phases in a ternary Re-Cr-Ni system were investigated at 1423 K by heat-treating various ternary Re-Cr-Ni alloys in vacuum for times up to 2000 h. The microstructures of the Re-containing alloys which had been water-quenched after various heating times were observed and their concentration profiles for Re, Cr and Ni were measured using an electron probe micro-analyzer. The Re-Cr-Ni alloys consisted of the σ phase with either the γ or δ phase. It was found that concentration profiles of the γ phase became flat after short heat treatment, but longer times of up to 2000 h were required to achieve the same effect for the σ and δ phases.
The tie-lined compositions(at%) of the each phase at 1573 K were experimentally determined as follows. The σ phase tie-lined with the γ phase(17.3Re, 20.6Cr and 62.1Ni) consists of 53.1Re, 25.5Cr and 21.4Ni. The σ phase tie-lined with the γ phase(16.9Re, 19.2Cr and 63.9Ni) consists of 53.0Re, 24.6Cr and 22.4Ni. The σ phase tie-lined with the γ phase(12.7Re, 24.8Cr and 62.5Ni) consists of 48.4Re, 30.9Cr and 20.7Ni. The σ phase tie-lined with the γ phase(6.1Re, 46.2Cr and 47.7Ni) consists of 28.1Re, 52.3Cr and 19.6Ni. The σ phase tie-lined with the δ phase(85.6Re, 5.2Cr and 9.2Ni) consists of 61.1Re, 27.7Cr and 11.2Ni.
