CoCrFeNiAl_(x)系高熵合金的动态力学性能和本构关系  

Dynamic mechanical properties and constitutive relations of CoCrFeNiAl_(x) high entropy alloys

作　　者：马胜国 王志华 MA Shengguo;WANG Zhihua(Institute of Applied Mechanics,College of Mechanical and Vehicle Engineering,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China;Shanxi Key Laboratory of Material Strength and Structural Impact,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China;National Experimental Teaching Demonstration Center of Mechanics,Taiyuan University of Technology,Taiyuan 030024,Shanxi,China)

机构地区：[1]太原理工大学机械与运载工程学院应用力学研究所,山西太原030024 [2]太原理工大学机械与运载工程学院材料强度与结构冲击山西省重点实验室,山西太原030024 [3]太原理工大学机械与运载工程学院力学国家级实验教学示范中心,山西太原030024

出　　处：《爆炸与冲击》2021年第11期1-11,共11页Explosion and Shock Waves

基　　金：国家自然科学基金(51501123,11390362);山西省“1331工程”重点创新团队建设计划。

摘　　要：高熵合金,以其独特的合金设计和优异的综合性能,成为当下材料研究的热点。本文利用高真空电弧熔炼法成功制备出了CoCrFeNiAl_(x)(x=0,0.6,1)系高熵合金,并通过分离式霍普金森压杆对其进行一系列不同应变速率下的动态压缩试验。通过X射线、扫描电镜和透射电镜分析,深入探索了该合金系的晶体结构、微观组织和变形特征。最后,利用修正后的Johnson-Cook(J-C)本构模型,获得了该体系高熵合金的动态本构关系。High-entropy alloys(HEAs),due to their unique alloy-design concepts and excellent comprehensive properties,are becoming a research hotspot nowadays.However,previous reports were scarcely focused on the dynamic mechanical loading of the HEAs,that is the applied strain rates often were limited in the quasi-static regime.In this research,CoCrFeNiAl_(x)HEAs were successfully prepared by vacuum arc melting pure elements in a high-purity argon atmosphere on a water-cooled Cu hearth.Each ingot was remelted at least five times to ensure its chemical homogeneity.Cylindrical samples with a diameter of three millimeters were then synthesized by copper-mould suction casting.Quasi-static compressive tests at room temperature were conducted by using an Instron 5969 testing machine,wherein the test specimens with an aspect ratio of 1∶1 were cut from the cylindrical samples along the longitudinal direction by electrical discharge machining.As a comparison,dynamic compression experiments with various strain rates were carried out at room temperature by the split Hopkinson pressure bar(SHPB).For characterization,crystal structure,microstructure and deformation characteristics were investigated in detail by a combination of X-ray diffraction(XRD),scanning-electron microscopy(SEM),and transmission-electron microscopy(TEM)analyses.The XRD results reveal that simple solid solution structures,in forms of face-centered cube(FCC)and/or body-centered cube(BCC),were obtained in the current alloys.All the alloys exhibit positive strain-rate sensitivity and excellent work-hardening ability.Interestingly,three isolated deformation mechanisms were detected by TEM analysis,that is combined dislocation slip plus deformation twinning dominats the plastic deformation in the CoCrFeNi alloy(with FCC structure)for both quasi-static and dynamic loading conditions,however,such phenomenon was only observed in the CoCrFeNiAl_(0.6) alloy(with FCC plus BCC structure)under dynamic loading.As for the CoCrFeNiAl alloy(with BCC structure),single dislocation

关 键 词：高熵合金 动态冲击 本构关系 变形机理 

分 类 号：O347[理学—固体力学] TG146.4[理学—力学]