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

Abstract

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 °C and 1200 °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 σ phase precipitates stable up to 1000 °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 α-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 (∼53 MPa) compared to FCC equiatomic HEAs.