TiB_2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

RELATIONSHIP BETWEEN MICROSTRUCTURE AND FATIGUE CRACK PROPAGATION BEHAVIOUR IN TiB_2 PARTICULATE REINFORCED ZA-8 Zn ALLOY

研究了ＴｉＢ２颗粒增强ＺＡ－８锌合金复合材料和基体材料的疲劳裂纹扩展行为与显微组织、断口的关系。结果表明：所研究复合材料的抗疲劳裂纹扩展能力优于基体材料，尤其在小裂纹阶段．其原因为：增强粒子与裂纹尖端的相互作用降低了裂纹尖端的应力强度；增强粒子与基体良好的界面结合力；增强粒子的加入，导致了基体微观组织结构的变化和细化以及增强粒子的桥接（Ｂｒｉｄｇｉｎｇ）作用。最后，探讨了在两种材料中不同的裂纹扩展机理。

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.