On the enhanced hardening ability and plasticity mechanisms in a novel Mn-added CoCrNi medium entropy alloy during high-pressure torsion

Microstructure and texture evolution during high-pressure torsion (HPT) of a novel Mn-added CoCrNi medium entropy alloy (Co33Ni33Cr19Mn15) is investigated for the first time. The alloy exhibited a rapid rise in hardness at relatively low shear strains (gamma <= 20). It is attributed to an extensive dislocation activity to achieve saturation in dislocation density of similar to 10(16) m(-2), combined TWIP and TRIP effects and microstructural refinement. At higher shear strain, hardness increased at much reduced rates owing to saturation of dislocation density, twin fault probability and the TRIP effect, besides continued grain refinement for severe nano-structuring led to subsequent strengthening. The FCC phase showed remarkable stability except a small degree of initial deformation-induced HCP martensitic transformation in an early stage of HPT. The ideal shear texture components were observed at low shear strain, and these continued to evolve up to 5 turns of HPT processing. For similar HPT processing conditions, the studied alloy showed superior hardness (similar to 650 Hv) compared to a wide spectrum of FCC materials, which is ascribed to a combination of the strengthening mechanisms of Taylor hardening, the TRIP and TWIP effects and Hall-Petch strengthening resulting from the nano-structured grains having an average size of similar to 35 nm. (c) 2022 The Author(s). Published by Elsevier B.V. CC_BY_4.

Effect of nickel addition on enhancing nano-structuring and suppressing TRIP effect in Fe40Mn40Co10Cr10 high entropy alloy during high-pressure torsion

The present work unravels the effect of nickel (Ni) addition on the deformation mechanism and hardness evolution in a Fe40Mn40Co10Cr10 high entropy alloy (HEA) during high-pressure torsion (HPT) processing. For this purpose, two variants of the high entropy Cantor alloy, with compositions (atomic%) Fe40Mn40Co10Cr10 (Ni0 alloy) and Fe35Mn35Co10Cr10Ni10 (Ni10 alloy) were selected. The study revealed a transition in the predominant plasticity mechanism with addition of Ni from TRIP in Ni0 to dislocation slip in Ni10 alloy. Such transition of plasticity mechanism was the direct consequence of an increase in the free energy of phase transformation, delta G(gamma ->epsilon) towards a more positive value with Ni addition. Interestingly, the Ni10 alloy showed a greater extent of nano-structuring than the Ni0 alloy with nearly three-fold refined grain sizes, that is, lesser than 30 nm in Ni10 alloy and ~90 nm in Ni0 alloy. Furthermore, a 3-4 times higher dislocation density was observed in the FCC phase of the Ni10 alloy compared to that in the transformed HCP phase in the Ni0 alloy for any given HPT processing conditions. These differences in mechanism(s) of deformation and the extent of nano-structuring manifested as a greater ability of Ni added Ni10 alloy to harden itself during HPT. The present study suggests that a large fraction of hard HCP phase originating from TRIP effect in the Ni0 alloy has a lower hardening ability than the high dislocation density and nano-structuring in the Ni10 alloy

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Abstracts of National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020

This book presents the abstracts of the papers presented to the Online National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020 (RDMPMC-2020) held on 26th and 27th August 2020 organized by the Department of Metallurgical and Materials Science in Association with the Department of Production and Industrial Engineering, National Institute of Technology Jamshedpur, Jharkhand, India. Conference Title: National Conference on Research and Developments in Material Processing, Modelling and Characterization 2020Conference Acronym: RDMPMC-2020Conference Date: 26–27 August 2020Conference Location: Online (Virtual Mode)Conference Organizer: Department of Metallurgical and Materials Engineering, National Institute of Technology JamshedpurCo-organizer: Department of Production and Industrial Engineering, National Institute of Technology Jamshedpur, Jharkhand, IndiaConference Sponsor: TEQIP-