摘要
难熔高熵合金在高温下表现出优异的性能,突破了传统高温合金的工作温度上限.我们采用原子模拟研究了化学元素分布和温度对等原子比MoNbTaW难熔高熵合金变形机制的影响.根据微观结构演化,建立了基于微观结构的本构模型,定量评估多种强化机制的贡献.结果表明,应变硬化后,流动应力随应变呈锯齿状剧烈波动.由于退火结构的溶质浓度降低,温度升高降低了应变硬化率和流动应力波动幅度.变形孪晶在变形机制中起着关键作用,能够通过位错基塑性和晶粒中的非晶形核进一步调节局部变形.有序结构的存在强烈影响了应力和应变分配.固溶强化和晶界强化对流动应力的贡献很大,孪晶强化对流动压力的贡献很小.原子模拟和力学模型为深入理解难熔高熵合金变形行为及性能的精确预测提供依据.
The equiatomic refractory high-entropy alloys(RHEAs)exhibit the excellent performance at high temperatures,breaking through the upper limits of operating temperatures in the conventional high-temperature alloys.Here,the influences of chemistry and temperature on the deformation mechanisms of the equiatomic MoNbTaW RHEAs are investigated,using the large-scale atomic simulations.According to the microstructure evolution,a microstructure-based constitutive model is established to study the effects of the multiple strengthening mechanisms.The results show the jagged sharp fluctuations of the flow stress with the strain after the strain hardening.The increasing temperature reduces the strain-hardening rate and the amplitude of fluctuations in the flow stress,due to the reduction of the solute concentration for the annealed structure.The deformation twinning plays a certain role in the deformation mechanism in comparison with dislocation,and the local deformation is further accommodated via the dislocation-based plasticity,and amorphous nucleation in the grains.The existence of the ordered structure affects the stress and strain partition dependent upon the mechanical properties.The solid solution strengthening and grain boundary strengthening contribute considerably to the flow stress,and twinning strengthening contributes relatively little to the flow stress.Our atomic simulation and model give valuable insights into the deep understanding of chemistry and temperature related to the deformation behaviour of RHEAs.
作者
李甲
任思危
刘彬
Peter K.Liaw
方棋洪
Jia Li;Siwei Ren;Bin Liu;Peter K.Liaw;Qihong Fang(State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body,College of Mechanical and Vehicle Engineering,Hunan University,Changsha,410082,China;State Key Laboratory of Powder Metallurgy,Central South University,Changsha,410083,China;Department of Materials Science and Engineering,The University of Tennessee,Knoxville,37996,USA)
基金
the National Natural Science Foundation of China(Grant Nos.U2267252,12172123,and 12072109)
the Natural Science Foundation of Hunan Province(Grant Nos.2022JJ20001 and 2021JJ40032)
the Science and Technology Innovation Program of Hunan Province(Grant No.2022RC1200)
the National Science Foundation(Grant Nos.DMR-1611180,1809640,and 2226508)
the Army Research Office(Grant Nos.W911NF-13-1-0438 and W911NF-19-2-0049).
