Impact of uneven distribution of grain characteristics on yield strength and martensitic transformation of as-hot-rolled medium-entropy alloys  

作　　者：Jungwan Lee Hyojin Park Sujung Son Jae Wung Bae Jin You Kim Sung Kyu Kim Jae-il Jang Hyoung Seop Kim 

机构地区：[1]Department of Materials Science and Engineering,Pohang University of Science and Technology(POSTECH),Pohang 37673,Republic of Korea [2]Department of Metallurgical Engineering,Pukyong National University,Busan 48513,Republic of Korea [3]Technical Research Laboratories,Energy and Shipbuilding Steel Research Group,POSCO,Pohang,Republic of Korea [4]Division of Materials Science and Engineering,Hanyang University,Seoul 04763,Republic of Korea [5]Graduate Institute of Ferrous&Eco Materials Technology(GIFT),Pohang University of Science and Technology(POSTECH),Pohang 37673,Republic of Korea [6]Center for Heterogenic Metal Additive Manufacturing,Pohang University of Science and Technology(POSTECH),Pohang 37673,Republic of Korea [7]Advanced Institute for Materials Research(WPI-AIMR),Tohoku University,Sendai 980-8577,Japan

出　　处：《Journal of Materials Science & Technology》2024年第10期234-245,共12页材料科学技术（英文版）

基　　金：POSCO(No.2021Y037);Nano&Material Technology Development Program through the National Research Foundation of Korea(NRF)funded by Ministry of Science and ICT(No.RS-2023-00281246);National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)(Nos.NRF–2021R1A2C3006662 and NRF-2022R1F1A1073796);J.L.acknowledges support from the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(No.RS-2023-00276120).

摘　　要：As-hot-rolled medium-entropy alloys(MEAs)with unevenly distributed grain sizes of face-centered cubic grains exhibit better yield strength without uniform elongation loss compared to cold-rolled and an-nealed ones.Successive operation of dynamic recrystallization(DRX)during several hot rolling passes leads to a wide range of grain sizes from submicrons to tens of micrometers due to the grain growth after nucleation:early recrystallized grains are coarser than recently recrystallized ones.Not only the grain size but internal dislocation density of the recently recrystallized grain is low.During the tensile deformation of the hot-rolled MEAs at-196 ℃,dislocation pile-ups in the relatively soft and fine DRX grains enhance yield stress and hetero-deformation-induced strain hardening.Thanks to the enhanced yield stress of the as-hot-rolled MEAs,stress-induced martensitic transformation easily occurs.Notably,partially DRXed MEAs hot-rolled at 800 ℃ have lower yield stress than fully DRXed ones,hot-rolled at 900 and 1000 ℃.This is attributed to the softening effect of the stress-induced body-centered cubic martensitic transformation in unrecrystallized coarse grains prior to the yielding,which lowers the yield stress of the partially DRXed ones.After yielding,the martensitic transformation facilitates strain hard-ening and early necking is precluded.This study presents a fresh outlook on the uneven distribution of grain sizes by hot rolling beneficial to mechanical responses of uniform elongation of~45%despite the as-rolled states with an advantage of simplified thermo-mechanical processes.

关 键 词：Dynamic recrystallization Nucleation and growth HETEROGENEITY Grain size distribution Deformation-induced martensitic transformation 

分 类 号：TG142.71[一般工业技术—材料科学与工程]