Mass transport in a highly immiscible alloy on extended shear deformation. (20th January 2023)

• Record Type: Journal Article
• Authors: Song, Miao; Liu, Jia; Ma, Xiaolong; Pang, Qin; Olszta, Matthew J.; Silverstein, Joshua; Pallaka, Madhusudhan R.; Sushko, Peter V.; Mathaudhu, Suveen N.; Powell, Cynthia; Devaraj, Arun; Gwalani, Bharat
• Is Part Of: Journal of materials science & technology. Volume 134(2023)
• Page Start: 197
• Page End: 208
• Publication Date: 2023-01-20
• Subjects: Tribology -- Immiscible alloys -- Nanostructures -- Shear deformation -- Forced mixing -- Atom probe; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2022.06.029
• Languages: English
• ISSNs: 1005-0302

Abstract

Highlights: Mechanism of shear assisted deformation in a high mixing enthalpy binary alloy (Cu-50 at.%Cr) are revealed using multimodal microstructural characterization techniques. During severe shear deformation, grain refinement in both Cu and Cr grains as a function of shear strain is captured revealing the extent of dynamic recrystallization. Cu NPs embedded in Cr maintain excellent coherent relationships with the surrounding Cr grains after deformation. Supersaturation difference as function of microstructural feature and shear strain are revealed using atom probe tomography, . Incoherency of Cr with the surrounding Cu grains impedes dislocations transmission from Cu to Cr and results in the formation of voids at the Cu/Cr interfaces and relative low mixing in the Cr nanoparticles. The formation of oxides near the surface prevents mass transport and forced mixing at the interface. Abstract: Forced mixing to a single-phase or supersaturated solid solution (SSS) and its prerequisite microstructure evolution in immiscible systems has been a focus of research for fundamental science and practical applications. Controlling the formation of SSS by shear deformation could enable a material design beyond conventional equilibrium microstructure in immiscible systems. Here, a highly immiscible Cu–50 at.% Cr binary alloy (mixing enthalpy of ∼20 kJ mol −1 ) was employed to investigate the microstructure evolution and localized tendencies of SSS during severe shear deformation. Our results demonstrate the dislocation mediated microstructural refinement process in each phase of the binary alloy and the mechanisms associated with localized solute supersaturation as a function of shear strain. Pronounced grain refinement in the softer Cu phase occurs owing to the strain localization driving the preferential dynamic recrystallization. The grain refinement of the Cr phase, however, is enabled by the progressive evolution of grain lamination, splitting, and fragmentation as a function of shear strain. The solute supersaturation is found to be strongly dependent on the local environments that affect the dislocation activity, including the level of microstructure refinement, the interfacial orientation relationship, the mechanical incompatibility, and the localized preferential phase oxidation. Ab initio simulations confirm that it is more favorable to oxidize Cr than Cu at incoherent Cu/Cr interfaces, limiting the mass transport on an incoherent boundary. Our results unveil the mechanism underpinning the non-equilibrium mass transport in immiscible systems upon severe deformation that can be applied to produce immiscible alloys with superior mechanical properties.