Significant annealing-induced hardening effect in nanolaminate d-nanotwinne d(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8)me dium-entropy alloy by severe cold rolling  

作　　者：Shuqing Yuan Hui Fu Lei Qian Chi Fai Cheung Xu-Sheng Yang 

机构地区：[1]State Key Laboratory of Ultra-precision Machining Technology,Department of Industrial and Systems Engineering,The Hong Kong Polytechnic University,Hung Hom,Kowloon,Hong Kong,China [2]Hong Kong Polytechnic University Shenzhen Research Institute,Shenzhen 518060,China

出　　处：《Journal of Materials Science & Technology》2024年第3期156-166,共11页材料科学技术（英文版）

基　　金：supported by the National Natural Science Foundation of China Project(No.51971187);Guangdong Basic and Applied Basic Research Foundation(No.2022A1515011322);PolyU Fund(No.G-YBZ3);funding support to the State Key Laboratories in Hong Kong from the Innovation and Technology Commission of the Government of the HKASR,China;SY and LQ were supported by grants from the Research Committee of PolyU under student account codes RK2J and RK2U,respectively.

摘　　要：Due to the easy coarsening caused by poor thermal stability,the verified annealing-induced hardening in nanograined metals can only maintain at a relatively low-temperature range.In this study,a nanolam-inated(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8)medium-entropy alloy with an average lamellae thickness of∼20 nm embedded by thinner nanotwins was fabricated by severe cold rolling to achieve superior thermal stability.Compared with the conventional nanotwinned CrCoNi with nanotwins inside ultra-fined grains,the hier-archical nanolaminated-nanotwinned(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8) exhibits a significant annealing-induced hard-ening effect,i.e.,hardness increasing from∼250 HV in the original specimen to∼500 HV in the cold-rolled status and finally∼630 HV after annealing at 600℃for 1 h.Detailed microstructure characterizations reveal that the reduced dislocation density and formation of L1_(2)ordered domain are mainly responsible for such hardening effect,which is facilitated by the effectively suppressed coarsening with annealing temperature,i.e.,slow detwinning process and well-retained low-angle nanolamellar structure.The coarsening mechanisms from the cold-rolled nanolamellae to the fully recrystallized micro-equiaxed structures under the annealing temperatures ranging from 400 to 800℃ were also elucidated by atomic observations.

关 键 词：Annealing-induced hardening Thermal stability Nanolaminated-nanotwinned structure CrCoNi Detwinning Grain boundary migration 

分 类 号：TG1[金属学及工艺—金属学]