TC17合金等轴组织和网篮组织的高周疲劳断口

High Cycle Fatigue Fractograph of TC17 Titanium Alloy with Equiaxed and Basket-waved Microstructure

对比分析了TC17钛合金2种典型组织形态(等轴组织和网篮组织)对高周疲劳断口形貌的影响。结果表明:2种组织的宏观疲劳断口均呈现出脆性断裂的特征,疲劳源区均位于试样表面,但是高周疲劳断口形貌却呈现显著差异,主要表现在宏观粗糙程度和微观形貌特征2个方面。宏观上看,等轴组织的疲劳断口较为平整,疲劳裂纹源区和扩展区的面积占断口面积的比例较大,网篮组织的疲劳断口则非常粗糙,表面起伏较大,疲劳断裂区占断口面积的比例较小。微观上看,2种组织形态的显微组织特征在断口形貌上均有体现,等轴组织的微观断口形貌较为细小,疲劳条带与组织中等轴α相具有相似尺寸;网篮组织的疲劳断口上可以看到α片层交织的形貌特征,二次裂纹遍布裂纹扩展的各个阶段,疲劳条带与等轴组织中的条带特征也有较大差异。

The effect of two typical microstructures(equiaxed and basket-waved microstructure) on the fracture morphylogy of high cycle fatigue(HCF) was investigated.The results show that the macro-fracture surface of the samples with both microstructures is charactered by brittle fracture and the fatigue crack initiates at the sample surface.The difference of the fractograph between the two microstructures is significant.On macro level,fractograph of equiaxed microstructure is quite smooth,and the fatigue crack area has a very large fraction of the whole facture surface.While fractograph of basket-waved microstructure is rough,and the fraction of fatigue crack area is relatively small.On micro level,the fatigue striation in equiaxed microstructure has a similar size with the primary α grain.While in basket-waved microstructure,basket-waved structure can be clearly seen in the fatigue fracture surface.Secondary cracks are more pervasive than in equiaxed microstructure.The fatigue striation also has a different morphology from equiaxed microstructure.