RELATIONSHIP BETWEEN MICROSTRUCTURE AND FATIGUE CRACK PROPAGATION BEHAVIOUR IN TiB_2 PARTICULATE REINFORCED ZA-8 Zn ALLOY
TiB2颗粒增强ZA—8锌合金的显微组织与疲劳裂纹扩展行为的关系

The relationships between microstructure, fracture surface and propagation behaviour of fatigue crack in TiB2 particulate reinforced ZA-8 Zn alloy and in the corresponding constitute matrix materials were studied. The present results indicate that the resistance to fatigue crack growth of the employed composite is in general superior to that of constitute matrix materials, especially for the short crack behaviour. This is attributed to (1) the interaction between particle and crack tip decreased the stress intensity ahead of the crack tip,(2) owing to the excellent interface strength,(3) the addition of reinforcement caused the change of matrix microstructure and refined the structure and (4) the bridging function of reinforcement. Finally, the mechanism for the difference in fatigue crack growth behaviour of the two materials was discussed. Correspondent HUA Wenjun, Beijing Institute of Aeronautical Materials, Beijing 100095