中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 35 No. 10 October 2025 |
（1. School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China;
2. School of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao 066004, China;
3. School of Materials Science and Engineering, Tianjin University, Tianjin 300354, China;
4. School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522, Australia）
Abstract:To explain the precipitation mechanism of χ phase in Co-based superalloys, the microstructural evolution of Co-Ti-Mo superalloys subjected to aging was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that the needle-like χ phase is mainly composed of D019-Co3(Ti,Mo), which is transformed from L12-γ′ phase, and a specific orientation relationship exists between them. χ phase is nucleated through the shearing of γ′ phase due to the influence of stacking fault. The crystal orientation relationship between L12 and D019 can be confirmed as {111}L12//{0001}D019, and á112？ L12//á1 00？ D019. The growth of D019-χ phase depends on the diffusions of Ti and Mo, and consumes a large number of elements. This progress leads to the appearance of γ′ precipitation depletion zone (PDZ) around D019-χ phase. The addition of Ni improves the stability of L12-γ′ phase and the mechanical properties of Co-based superalloys.
Key words: Co-based superalloy; χ phase precipitation; γ′ phase; stacking fault; crystal orientation relationship
