D0_(22)相强化型Ni_(2)CoCrFeNb_(0.15)高熵合金的变形机理

Deformation mechanism of D0_(22)-hardened Ni_(2)CoCrFeNb_(0.15) high entropy alloy

采用透射电子显微镜和扫描电子显微镜的背散射电子衍射及电子隧道衬度成像技术研究了D0_(22)相强化型Ni_(2)CoCrFeNb_(0.15)高熵合金在单轴拉伸变形过程中的织构演化、变形亚结构特征、位错与析出相交互作用以及断裂行为。结果表明:位错的平面滑移主导了该合金的单轴拉伸变形,D0_(22)超点阵相是促进位错平面滑移的主要因素。因位错的平面滑移模式产生的平面滑移带随着应变量的增加,其密度随之增加,平均间距随之减小。变形过程中先形成{001}织构,然后{111}织构增强,最终获得典型的{001}和{111}拉伸织构。当合金在单独拉伸变形过程中达到最大应力时,晶界处萌生裂纹并扩展为断裂主裂纹,导致塑性变形失稳。

In the present study,the texture evolution,deformation substructure characteristics,dislocation-precipitate interaction and fracture behavior of the D0_(22)-hardened Ni_(2)CoCrFeNb_(0.15) high entropy alloy during uniaxial tensile deformation were evaluated by transmission electron microscope(TEM),electron backscatter diffraction(EBSD)and electron channeling contrast imaging(ECCI)based on scanning electron microscope.The results show that the plane slip of the dislocation dominates the uniaxial tensile deformation of the alloy,and the D0_(22) superlattice phases are the main factor to promote the plane slip of the dislocation.The plane slip mode of the dislocation leads to the plane slip band as the characteristic deformation substructure.When the strain level increases,the plane slip band density increases and the mean distance decreases.In the deformation process,the{001}texture is formed first,then the{111}texture is enhanced,and finally the typical{001}and{111}tensile textures are obtained.When the stress reaches maximum value during uniaxial tensile deformation,the cracks originate the grain boundary and further propagate to form the main fracture crack,resulting in plastic instability.