氧化镧弥散强化钼合金裂纹扩展的TEM原位观察

TEM in situ Observation of Crack Propagation in Lanthanum Oxide Dispersion Strengthened Molybdenum Alloy

摘要:

采用透射电子显微镜动态拉伸技术对氧化镧弥散强化钼合金的裂纹扩展过程进行原位观察。发现裂纹的扩展模式受基体晶粒尺寸与氧化镧颗粒的形状和尺寸影响。裂纹尖端遇到非常细小的晶粒时会发生沿晶界扩展；裂纹尖端遇到棒状微米级粗大氧化镧颗粒时，裂纹穿过氧化镧颗粒扩展；遇到椭球状亚微米级氧化镧颗粒时，裂纹越过氧化镧颗粒扩展，并发生裂纹扩展方向的偏转；而当裂纹扩展到细小的球状纳米级氧化镧颗粒时会被阻止，裂纹以“Z”字型或跨接的方式继续扩展。根据实验结果从裂纹扩展方式和能量耗散角度对氧化镧弥散钼合金的细晶增韧和颗粒增韧机制进行分析和讨论。

Abstract:

The processes of crack propagation in the La2O3-dispersed-strengthened molybdenum alloy were studied by in situ observation of transmission electron microscope. The results show that the paths of crack propagation in the alloy are dependent on the grain size of the molybdenum matrix and the shape and size of La2O3 particles. The crack propagates along the grain boundary of the matrix when it meets very fine molybdenum particles; the crack directly passes through the La2O3 particles to propagate when it meets micron-sized coarse rod-shaped La2O3 particles; the crack detours the particles and deflects when it meets sub-micron-sized ellipsoid-shaped La2O3 particles; the crack is pinned and then goes on propagating in zigzag or by bridging when it meets the nanosized fine and spherical La2O3 particles. Based on these experimental results, the mechanism of fine-grain toughening and particle-toughening of La2O3-dispersed- strengthened molybdenum were discussed from the aspect of the crack propagation paths and energy dissipation.