Abstract
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)97.4Al0.8Ti18 medium-entropy alloy with an average lamellae thickness of～20 nm em-bedded 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)97.4Al0.8Ti18 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 charac-terizations reveal that the reduced dislocation density and formation of L12 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.
基金项目
国家自然科学基金(51971187)
Guangdong Basic and Applied Basic Research Foundation(2022A1515011322)
PolyU Fund(G-YBZ3)
State Key Laboratories in Hong Kong from the Innovation and Technology Commission of the Government of the HKASR,China()
Research Committee of PolyU(RK2J)
Research Committee of PolyU(RK2U)
NETL
NSTL
万方数据