Creep-coordinated behaviors of the σ phase with stacking disordering defects in a Ni-based single crystal superalloy

Ni-based single crystal superalloys (Ni-SXs) generally precipitate unfavorable topologically close-packed (TCP) phases at elevated temperatures. Conventional design strategies primarily aim to suppress TCP phase formation; however, this approach often involves an unavoidable trade-off between material cost and creep resistance. To tackle the dilemma, we designed a creep-coordinated TCP phase (σ phase) in a Ni-SX through harnessing the (001)_σ stacking disordering defects. Here, based on atomic-scale analysis and first-principles calculations, we systematically elucidate the roles of the (001)_σ stacking disordering defects in facilitating creep-coordinated behaviors of the σ phase, which include the self-regulation of interface mismatches, the transformation of growth patterns, and the cooperative deformations with the matrix. These behaviors enable the σ phase to optimize the adaptability for interface mismatches, promote morphological spheroidization, and break through the traditionally hard and brittle nature, thereby supporting the outstanding creep performance of the Ni-SX. Our work presents an effective and sustainable strategy for improving the microstructure stability and performance of Ni-SXs, providing novel insights into high-performance alloy design through manipulating the TCP (σ) phase.