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通过二元铝锂合金的细观拉伸疲劳实验，动态观察了试样表面金相微观结构组织的变化及微裂纹的萌生及扩展直到断裂的全过程，并分析讨论了晶界及微结构对微裂纹萌生及扩展的影响，微裂纹向短裂纹、长裂纹发展的判据。本实验材料是模型材料，晶界结合强度较弱，裂纹沿晶开裂现象较多。经对实验结果及金相裂纹分析，表明金属材料微结构对裂纹扩展有明显的影响。晶界作为一种物质界面存在于晶粒间，具有一定的物理和力学性质，对微裂纹扩展速率及发展行为有较大影响。
Through the meso-tensile fatigue test of binary Al-Li alloy, the change of the microstructure and the initiation and propagation of the micro-cracks in the microstructure of the sample were observed dynamically. The effects of grain boundary and microstructure pairs Influence of microcrack initiation and propagation, criterion for the development of microcracks to short cracks and long cracks. The experimental material is a model material, the grain boundary bonding strength is weak, crack along the crystal crack phenomenon more. The experimental results and the analysis of the microstructure cracks show that the microstructure of the metal material has a significant effect on the crack propagation. As a material interface exists in grain boundaries, the grain boundaries have certain physical and mechanical properties, and have a great influence on the rate of microcrack propagation and development behavior.