Microstructure effects on fatigue crack growth in additively manufactured Ti–6Al–4V
Microstructure effects on fatigue crack growth in additively manufactured Ti–6Al–4V
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DOI：
10.1016/j.msea.2020.139993
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发表时间：
2020-09
期刊：
影响因子：
6.4
通讯作者：
R. VanSickle;David Foehring;H. Chew;J. Lambros
中科院分区：
文献类型：
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作者：
R. VanSickle;David Foehring;H. Chew;J. Lambros
在这项工作中，我们研究了增材制造（AM）直接金属激光沉积Ti-6Al-4V合金的不同显微组织特征与观察到的疲劳和断裂行为之间的关系，采用高分辨率数字图像相关实验和显微组织成像。观察到AM试样中的疲劳裂纹周期性地平行于α′条扩展，并在先前的β晶界处偏转。相应的塑性应变分布呈现出与α′板条相关的针状高应变区，表明微观组织对塑性区有显著影响。在许多情况下，疲劳裂纹也向附近未烧结粉末或气体夹持的空隙扩展。在一些实验中，AM试样在单调断裂或循环疲劳载荷下发生过早破坏，我们将其归因于裂纹尖端附近存在空洞团簇。这些疲劳和断裂特征在不同构建方向的AM样品中是相似的。
In this work we investigate the relationship between the different microstructural features in additively-manufactured (AM) Direct Metal Laser Deposited Ti–6Al–4V alloys and the observed fatigue and fracture behaviors, using high resolution Digital Image Correlation experiments and microstructural imaging. Fatigue cracks in the AM specimens were observed to periodically propagate parallel to the α' laths and deflect at prior β grain boundaries. Corresponding plastic strain distributions show needle-like regions of high strain that correlated to the α' laths, suggesting significant influence of the microstructure on the plastic zone. In many cases, the fatigue cracks also propagated towards voids from unsintered powder or gas entrapment in the vicinity. In several experiments, premature failure of the AM specimens occurred under monotonic fracture or cyclic fatigue loading, which we attribute to the presence of void clusters located near the crack-tip. These fatigue and fracture characteristics were similar for AM specimens of different build-orientations.