The influences of Al/Ti ratio and Al+Ti content on microstructural and mechanical property stability of a Ni–Fe–Cr-based superalloy

The effects of Al/Ti ratio and Al + Ti content on microstructural evolution and tensile properties of a Ni–Fe–Cr-based superalloy (named GH2107 alloy) were investigated during long-term aging at 750 °C for up to 10,000 h. The results show that the amount of MC carbides can be increased by the lower Al/Ti ratio or higher Al + Ti content, which effectively suppresses M 23 C 6 carbides formed at the grain boundaries (GBs). During long-term aging, the thermal stability of γ′ phase can be enhanced by decreasing the Al/Ti ratio, since it reduces the γ/γ′ lattice misfit. However, Al and Ti elements have little influence on the growth rate of γ′ phase. As the Al/Ti ratio decreases or the Al + Ti content increases, the yield and tensile strengths are improved significantly due to the intensified γ′ strengthening effect. A reduction in the Al/Ti ratio is more effective in mitigating performance deterioration than an increase in the Al + Ti content, as it results in a lower amount of σ/Laves phases. The precise composition design strategy developed here provides a new paradigm for developing Ni–Fe–Cr-based superalloys.