Abstract
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.
基金项目
POSCO(2021Y037)
Nano & Material Technology Development Program through the National Research Foundation of Korea(NRF)funded by Ministry of S(RS-2023-00281246)
National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)(NRF-2021R1A2C3006662)
National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)(NRF-2022R1F1A1073796)
Basic science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(RS-2023-00276120)
NETL
NSTL
万方数据