Stress-dependent creep behavior and deformation mechanisms in a Ni3Al single-crystal alloy under 1200℃ ultra-high temperature

A novel Ni 3 Al-based single crystal superalloy was subjected to creep testing at 1200 °C under applied stresses ranging from 60 to 100 MPa. The stress-related deformation mechanism was elucidated through creep performance testing and examination of microstructure evolution. The creep life decreased from 360.5 h to 22.6 h as the stress increased from 60 to 100 MPa. while the minimum creep rate increased from 5.02 × 10 -9 s - 1 to 2.77 × 10 - 7 s - 1. A single Norton-law fit over the entire stress range yielded an overall apparent stress exponent of n = 7.43.Increasing applied stress accelerated γ′ rafting and topological inversion, while also increasing the spatial heterogeneity of the γ/γ′ interfacial dislocation network, as evidenced by the emergence of bimodal dislocation-spacing distributions at 90 and 100 MPa. Meanwhile, dislocation climb remained a readily activated deformation mode throughout the nominal stress range. At 100 MPa, particularly during tertiary creep, local true-stress amplification and interfacial dislocation accumulation further enhanced dislocation activity within the γ′ phase, thereby increasing the relative contribution of γ′ shearing. In summary, this study reveals stress-dependent deformation behavior and microstructural evolution under varying stress conditions at 1200℃, providing foundational data for the material selection of turbine blades in advanced aeroengines.