Topologically inverse microstructure in single-crystal superalloys: microstructural stability and properties at ultrahigh temperature

Topological phase inversion, in which γ'-precipitate becomes topological matrix phase, is a typical ‘detrimental’ microstructural degradation in Ni-based single-crystal superalloys. Here, a topologically inverse structure without service-induced damages is proposed. This structure exhibits excellent stress rupture properties at 1200°C and great microstructural stability, characterized by high, steady two-phase interface density. The relationship of the interface density to microscopic dislocation motion and macroscopic plastic deformation has been established, which reveals possible strengthening effect. These results will help understanding the benefit from this ‘degraded’ but quite stable microstructure and guide microstructure tuning against long-termed heat-resisted service.