Microstructure and texture of heavily cold-rolled and annealed extremely low stacking fault energy Cr26Mn20Fe20Co20Ni14 high entropy alloy: Comparative insights

Microstructure and crystallographic texture of an extremely low stacking fault energy (SFE) FCC single-phase Cr26Mn20Fe20Co20Ni14 high entropy alloy (HEA) was investigated and compared with selected low SFE FCC HEAs. The Cr26Mn20Fe20Co20Ni14 HEA was 90% cold-rolled and annealed between 750 degrees C and 1200 degrees C. The microstructural evolution revealed nano-twins, extensive shear bands, and gradual evolution of deformation-induced lamellar nanostructure. Evidence of deformation-driven FCC -> HCP transformation was indicated after heavy cold-rolling. Concomitant to microstructural evolution, the formation of a predominant brass-type ({110} < 112 >) texture after heavy cold-rolling was confirmed. Annealing resulted in the formation of (Co, Cr) rich sigma phase precipitates stable up to 1000 degrees C but dissolved in the FCC matrix at higher annealing temperatures. The pinning effect exerted by the precipitates resulted in considerable hindrance to grain growth compared to other FCC HEAs, whereas dissolution of the precipitates resulted in extensive grain growth. Annealing textures retained alpha-fiber (normal direction (ND)// < 001 >) components and also showed a high volume of random components. These observations highlighted the limited contributions of preferential nucleation and growth. Broadly, the annealing texture showed remarkable resemblance with other low SFE HEAs. An appreciable strength-ductility balance could be observed in the suitably annealed HEA. Meanwhile, Hall-Petch analysis indicated a significantly lower lattice friction stress (similar to 53 MPa) compared to FCC equiatomic HEAs. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the microstructure and crystallographic texture of an extremely low stacking fault energy high entropy alloy. Various changes and phase transformations were observed during heavy cold-rolling and annealing processes. The annealing texture showed remarkable resemblance with other low stacking fault energy alloys, and the suitably annealed alloy exhibited appreciable strength-ductility balance.