应变速率对HCP/FCC双相CoCrFeNiNb_(0.5)高熵合金力学性能的影响  

Effect of strain rate on mechanical properties of HCP/FCC dual-phase CoCrFeNiNb_(0.5)high-entropy alloy

作　　者：马自豪 侯兵[1] 秦冬阳 李玉龙[2] 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)

机构地区：[1]西北工业大学航空学院,西安710072 [2]西北工业大学民航学院,西安710072

出　　处：《Transactions of Nonferrous Metals Society of China》2023年第4期1144-1155,共12页中国有色金属学报（英文版）

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)。

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.

关 键 词：高熵合金 共析结构 高应变速率 剪切 韧-脆转变 

分 类 号：TG139[一般工业技术—材料科学与工程]