Speaker
Description
Dislocation dissociation assisted formation mechanism of σ phase and its impact on producing heterogeneous lamella microstructure in CoCrV medium-entropy alloy.
Luda Wang1, 2, 4, Hai-Le Yan1, Yudong Zhang2, 4, Benoit Beausir2, 4, Weimin Gan3, Peltier Laurent2, Nathalie Siredey-Schwaller2, Claude Esling2, Xiang Zhao1, Liang Zuo1
1 Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819, China
2 Université de Lorraine, CNRS, Arts et Metiers ParisTech, LEM3, Metz, France
3 German Engineering Materials Science Center at MLZ. Helmholtz-Zentrum hereon, Garching, Germany
4 Laboratory of Excellence on Design of Alloys for low-mAss Structures (DAMAS), Université de Lorraine, Metz, France
Abstract:
Controlling the σ phase is crucial for balancing its strengthening effects while preventing embrittlement. However, the specific influence of dislocation activity on its formation remains unclear. In this work, an FCC-structured Co66.66Cr16.67V16.67 MEA prone to σ phase formation under non-equilibrium conditions. After cold rolling and heat treatment, in-situ and ex-situ diffraction techniques revealed ultra-rapid, spatially inhomogeneous precipitation of nano-sized σ particles, enriched in Cr and V but depleted in Co, mainly in severely deformed regions. This rapid formation was driven by defect-assisted atomic segregation and structural transformation via dislocation dissociation. The similarity of the atomic arrangement of the partial dislocations to that of the {001} sigma planes provides favorable structure transformation stimulus, enabling an FCC {111} to σ {001} orientation inheritance and a specific σ texture. Owing to the spatially inhomogeneous precipitation, a heterogeneous lamellar microstructure was formed, composed of alternatively distributed fine dual-phased layers and coarse single-phased layers. This work provides comprehensive information of dislocation-dissociation-assisted formation mechanism of σ phase.
