Re-precipitation mechanisms of the γ′ phase with sphere, near-sphere, cubic, octets and finally-dendrite in as-cast Ni-based superalloys

[摘要] The morphology and size distribution of gamma' phases have a significant impact on the thermal processing and manufacturing of components made of superalloys and their service performance under adverse conditions. The homogenization treatment of as-cast superalloys ingot is the first modulation of the morphology, size distribution and other characters of gamma' phase. Therefore, investigation on the re-precipitation mechanism of gamma' phase is of critical theoretical value and engineering significance. In this research, the morphology evolution and size distribution of re-precipitation gamma' phase in an as-cast Ni-based superalloy during homogenizing treatment were investigated extensively and systematically. The re-precipitation mechanism of gamma' phase with sphere, near-sphere, cubic, octets and finally-dendrites was identified under various cooling conditions. The gamma' phase size is increased while the nucleation density is decreased with the cooling conditions changing from air cooling (AC) to furnace cooling (FC). The gamma' phase stability during growth was discussed and the reprecipitation gamma' phase is generated from a refine spherical shape at fast cooling condition (AC); while irregularity growth even splitting happened at slow cooling condition (FC). The findings help understand the re-precipitation mechanism of the gamma' phase of Ni-based superalloys and provide a basis for controlling of the microstructure and tailoring of the properties of the alloys. (C) 2021 Elsevier B.V. All rights reserved.

[发布日期] 2021-09-25

[关键词] Re-precipitation mechanism;gamma ' phase;Ni-based superalloys;Sphere, near-sphere, cubic, octets and finally dendrites;Phase stability