采用双重退火对Ti8LC低成本钛合金进行热处理,测试其拉伸性能,并对其疲劳裂纹扩展行为进行研究,探索其疲劳断裂机制.结果表明,提高双重退火的第1次退火温度,强度略有升高,塑性降低.da/dN试样断口3个区特征明显:预裂区为解理断裂机制.稳态扩展区裂纹以条纹循环机制向前扩展,同时能观察到很多二次裂纹.快速扩展区的断口呈韧窝型断裂特征.该合金的疲劳裂纹扩展速率对退火温度不敏感.
Low-cost titanium alloy Ti8LC was heat treated by duplex annealing. Its tensile properties were tested, and the fatigue crack propagation behavior as well as fatigue fracture mechanism were studied. Results show that the strength of the alloy increases a little but the ductility decreases with the increase of the first annealing temperature. SEM analysis on the fatigue crack propagation was performed, and the analysis results indicate that the fatigue crack propagates in three modes of three regions. The presplitting region was cleavage fracture. In the stationary state growth region, fatigue crack grew ahead in the form of striation mechanism and many second fatigue cracks were observed in the meantime. In the fast-growth region is mainly dimple. The temperature of duplex annealing has little influence on fatigue crack propagation behavior.
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