摘要
利用分离式霍普金斯压杆、扫描电子显微镜和透射电子显微镜研究应变速率对铸态CoCrFeNiNb_(0.5)高熵合金力学行为的影响。CoCrFeNiNb_(0.5)高熵合金由先共析密排六方(HCP)相和共析组织构成,合金的共析结构为片层状的HCP相和片层状的面心立方(FCC)相。当应变率从1×10^(-4)s^(-1)增加至6×10^(3)s^(-1)时,合金的屈服强度不会显著增加;然而,合金的破坏应变剧烈降低。片层状HCP相的准静态塑性变形机理为缠结状位错的增殖,而其动态塑性变形机理转变为剪切。片层状HCP相的剪切变形能够导致CoCrFeNiNb_(0.5)高熵合金在低压缩应变(ε=0.1)下形成微裂纹。由于片层状HCP相中微裂纹的数量随着动态压缩应变的提高而增加,微裂纹的扩展引发材料的雪崩式断裂。因此,铸造态CoCrFeNiNb_(0.5)高熵合金表现出显著的应变速率诱发脆性特性。
By using split-Hopkinson pressure bar,scanning electron microscope and transmission electron microscope,the influence of strain rate on mechanical behavior of the as-cast CoCrFeNiNb_(0.5)high-entropy alloy(HEA)consisting of hexagonal close-packed(HCP)pro-eutectic phase and eutectic structure(HCP laminate and face-centered cubic(FCC)laminate)was investigated.As the strain rate increases from 1×10^(-4)to 6×10^(3)s^(-1),it is found that yield strength does not increase evidently and that fracture strain drops drastically.Quasi-static deformation mechanism of HCP laminate is the multiplication of tangled dislocation.However,the dynamic deformation mechanism of HCP laminate is shearing.Shearing may lead to the formation of the micro-crack at low compression strain of 0.1.Since the number of the micro-crack increases rapidly with the increase of dynamic compression strain,the avalanche fracture of HEA,which is caused by the covalence of micro-crack evolved from the shearing of HCP laminate,occurred,contributing to the dynamic compressive embrittlement.
作者
马自豪
侯兵
秦冬阳
李玉龙
Zi-hao MA;Bing HOU;Dong-yang QIN;Yu-long LI(School of Aeronautics,Northwestern Polytechnical University,Xi’an 710072,China;School of Civil Aviation,Northwestern Polytechnical University,Xi’an 710072,China)
基金
supported by the National Natural Science Foundation of China(Nos.11872317,11972310)
the Project of Key Laboratory of Impact and Safety Engineering(Ningbo University),Ministry of Education,China(No.CJ202208)
Science Challenge Project,China(No.TZ2018001)。
关键词
高熵合金
共析结构
高应变速率
剪切
韧-脆转变
high-entropy alloy
eutectic structure
high strain rate
shearing
ductile-to-brittle transformation
作者简介
Corresponding author:Dong-yang QIN,Tel:+86-15291457041,E-mail:qindongyang19831205@126.com;Corresponding author:Yu-long LI,Tel:+86-29-88494859,E-mail:liyulong@nwpu.edu.cn。
