内生非晶复合材料在高速率动态冲击下的力学响应机理

In-situ dendrite reinforced metallic glass matrix composites exhibit super-high strengths, which renders them potential candidates as new structural metallic materials. For actual structural applications,the service conditions are very complex, and the extreme conditions must be considered. In this study, the mechanical response mechanisms of in-situ metallic glass matrix composites upon dyanmic compressive loading will be investigated in detail. Firstly,the strain-rate sensitivity and fracture features of in-situ composites are explored.And the mechanical properties upon dynamic loading can be obtained. Secondly,the structural changes of metallic glass matrix, interior of dendrites, and the interface between these two phases are investigated. The physical nature of in-situ composites with different microstructures under high-speed dynamic loading are revealed.The physical mechanisms for the dynamically fractured in-situ metallic glass matrix composites are clarified. Finally,the constitutive relation is based on the dyanmic mechanics, which would quantify the mechanical properties and the microstructure of in-situ dendrite reinforced metallic glass matrix composites. Consequently, the mechanical response mechanisms of in-situ metallic glass matrix composites upon dyanmic compressive loading will be revealed.The present study will provide theoretical supports for the safe service of promising in-situ dendrite reinforced metallic glass matrix composites.

内生树枝晶增韧的非晶基复合材料极具作为新型结构金属材料的潜质。对于结构材料，实际的复杂多变的服役环境，如极端条件必须加以考虑，本研究将探讨内生非晶复合材料在高速率动态冲击下的力学响应机理。首先，探明不同微观组织的内生非晶复合材料的速率敏感性特征及其断裂特性，对比掌握在动态冲击加载条件下的力学性能；然后，系统地研究不同微观组织在高速率动态冲击下变化的物理本质，从非晶基体、树枝晶内部和两相界面三方面出发分析在动态冲击失效后的结构变化，得出复合材料在动态冲击下的物理响应机制；最后，构建动态冲击下的本构方程来对应力学行为，从理论上使得动态冲击下的力学性能变化与本征方程对应的变形阶段有机联系在一起。该研究将从实验和理论上得出内生非晶复合材料在动态冲击下的力学响应机理，为该类型复合材料在冲击载荷作用下安全服役提供理论保障。

内生树枝晶增韧的非晶基复合材料极具作为新型结构金属材料的潜质。对于结构材料，实际的复杂多变的服役环境，如极端条件必须加以考虑，本研究探讨了内生非晶复合材料在高速率动态冲击下的力学响应机理。本项目研究中，设计并制备了Ti40Zr24V12Cu5Be19、Ti48Zr18V12Cu5Be17、Ti58Zr16V10Cu4Be12、Ti60Zr14V12Cu4Be10、Ti62Zr12V13Cu4Be9和Ti50Zr18Ni5Ta15Be12六种非晶复合材料。研究发现，当第二相树枝晶呈现粗大且网络状分布时，非晶复合材料在动态冲击时产生宏观塑性变形。微观上，枝晶内部变形中出现了大量的位错并滑移到边界，位错的堆积甚至产生剪切台阶，有效地提高了晶体边界的强度并阻碍了剪切带扩展传播，促进了剪切带数量密度的增殖，使得材料宏观上表现出极大的塑性。唯象地采用晶体材料在动态冲击时常用的Johonson-Cook模型作为内生非晶复合材料变形的宏观本构方程。从非晶剪切软化角度出发，构建了高应变速率下的C-S微观本构方程。从理论上使得动态冲击下的力学性能变化与本构方程对应的变形阶段有机地联系在一起，为该类型复合材料在冲击载荷作用下安全服役提供理论保障。