Influence of γ′ phase on the microstructural evolution and compressive properties of Ni-based single crystal superalloys

Abstract

To facilitate the evaluation and prediction of hot-end component performance, scanning electron microscopy and quasi-static compression tests were carried out on Ni-based single crystal superalloys, and the influence of γ′ phase on microstructural evolution and compressive properties was systematically investigated. Results show that γ′ phases exhibit spherical, cubic, or lath-like morphologies, and their average size increases from ∼ 180  nm to ∼ 450  nm after thermal exposure; and superalloys with higher volume fraction of γ′ phase gradually precipitate topologically close-packed (TCP) phase. The compressive properties display pronounced anisotropy, governed by both microstructure and loading direction. For superalloys with lower volume fraction of γ′ phase, yield strength decreases from 670  MPa to 505 MPa and ultimate compressive strength from 4690  MPa to 4240 MPa as the γ′ phase coarsens. In contrast, for superalloys with higher volume fraction of γ′ phase, ultimate compressive strength initially decreases and then increases, accompanied by rise in failure strain from 22 % to 46 % after thermal exposure. With increasing loading angle, ultimate compressive strength initially decreases and then rises, whereas yield strength, failure strain and hardening modulus exhibit more complex trends. These variations are closely related to γ′ and TCP phase, and microstructure and loading direction collectively affect mechanical behavior.