Stacking-fault networks with Lomer-Cottrell locks induced by carbon addition in a severely strained Cr-Co-Ni alloy

Author(s)

Stumpf, Guilherme Cardeal ; Bertoli, Gustavo ; Coury, Francisco Gil ; Neta, Augusta Cerceau Isaac ; Montoro, Luciano Andrey ; Figueiredo, Roberto Braga ; Wolf, Witor

• Document type: Journal article
• Source: Journal of Alloys and Compounds; v. 1033, p. 12-pg., 2025-06-20.

Abstract

Face-centered cubic (FCC) Cr-Co-Ni multi-principal element alloys are among the toughest materials ever designed. The optimal trade-off between strength and ductility shown by these materials is tied with their deformation evolution. Typically, their plastic deformation starts with dislocation slip, followed by mechanical twinning (i.e., twinning induced plasticity, TWIP) and, as strain levels further increase, phase transformation induced by plasticity (TRIP). This work evaluates the deformation substructure of a highly strained (achieved with high-pressure torsion) Cr40Co30Ni30 (at%) alloy with and without carbon alloying. After processing, the carbon-free alloy developed a typical substructure observed in FCC Medium/High-entropy alloys at later stages of straining, characterized by the presence of nanotwins and HCP lamellae, resulting in a 5.9 GPa hardness. In contrast, carbon addition induced grain refinement and suppression of the TWIP and TRIP effects. Notably, the Cr39.6Co30Ni30C0.4 alloy developed networks of stacking faults with partial dislocations and Lomer-Cottrell locks, which primarily contributed to a stronger hardening capability, resulting in an increased hardness of 7.3 +/- 0.8 GPa, 22 % (1.3 GPa) higher than the base alloy. These findings have important implications for better understanding the deformation substructure evolution of FCC multi-principal element alloys and can pave the way forward in regard to the design approaches for carbon-alloying in these materials. (AU)

• FAPESP's process: 23/07403-5 - Short-Range Order (SRO) in medium and high entropy alloys: design and characterization
• Grantee: Guilherme Cardeal Stumpf
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 22/02770-7 - Integrated Computational Materials Engineering ICME: applied to modeling, production, characterization and testing high entropy alloys
• Grantee: Francisco Gil Coury
• Support Opportunities: Research Grants - Initial Project