飞片冲击加载下Fe50Mn30Co10Cr10合金的动态损伤研究

Dynamic Damage Evolution in FeMnCoCr Alloy Under Shock Loading of Flyer Plate

采用一级轻气炮对2种预处理状态下的Fe50Mn30Co10Cr10高熵合金进行了冲击加载,利用多普勒测速系统对加载中样品自由面粒子进行速度测量;通过背散射电子衍射、金相显微镜探究了Fe50Mn30Co10Cr10高熵合金的初期层裂特征。结果表明:马氏体和孪晶对层裂初期孔洞的形核、长大,裂纹的扩展有重要影响。孔洞并非在基体/马氏体的相界面间形核,而是优先形核于基体的晶界中,再沿基体相内部聚集形成微裂纹。与静态加载不同,动态载荷下孔洞的形核受孪晶界限制,微裂纹的拓展受马氏体阻碍,其方向并非完全与冲击方向垂直。冷轧退火试样中,晶界密度大,孔洞形核多,损伤程度较大,层裂强度低,而含有较多马氏体的热轧退火试样中裂纹扩展慢,最终损伤程度较小,层裂强度高。

The Fe50Mn30Co10Cr10 high-entropy alloy after two kinds of pre-treatment was shock-loaded respectively by a first-stage light gas gun.The velocity of free surface particles of the sample during the loading process was measured with the Doppler pin system,and the initial spallation evolution of the alloy was investigated by using back scattered electron diffraction and metallographic microscope.The results show that martensite and twins boundary have important effects on the nucleation,coalescence and crack propagation in the initial stage of spallation.The voids are preferentially nucleated in the grain boundaries of the matrix,instead of the matrix/martensitic phase interface,and then aggregate within the matrix phase to form microcracks.Unlike static loading,the nucleation of voids under dynamic loading is limited by twin boundaries,and the microcracks propagation,due to being hindered by martensite,is not perpendicular to the impact direction.The cold-rolled and annealed samples are characterized by higher density of grain boundaries,more nucleation of voids,higher degree of damage and lower spallation strength.In comparison,the hot-rolled and annealed samples containing more martensite are characterized by lower crack propagation and lower final damage,as well as higher spallation strength.