An experimental protocol has been set up in order to study the low cycle fatigue (LCF) damage micromechanisms in a lost foam casting (LFC) A319 alloy at room temperature. The microstructure of the alloy was characterized by using X‐ray computed tomography (X‐ray CT) prior to the LCF tests performed with surface in situ observations using a long distance microscope, which allow crack initiation and propagation being tracked in real‐time. The mechanical fields measured by digital image correlation (DIC) method allowed establishing the relations between strain localizations, damage evolutions and microstructure while a developed etching method, which gives a natural texture to the surface, makes DIC feasible to an acceptable resolution without masking the microstructure. The results showed that crack initiation is ascribed to strain localizations induced by large pore and/or the propagation of a previously nucleated crack. Cracks propagate along hard inclusions but the orientation of hard inclusions has also an influence on crack path.

中文翻译：

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X射线计算机断层摄影术与表面原位分析相结合并结合数字图像相关方法研究消失模铸造A319合金的低周疲劳损伤微观机制

为了研究室温下失泡沫铸件（LFC）A319合金中的低周疲劳（LCF）破坏微观机制，已经建立了实验方案。在使用长距离显微镜对表面进行原位观察的LCF测试之前，使用X射线计算机断层扫描（X射线CT）对合金的微观结构进行了表征，从而可以实时跟踪裂纹的萌生和扩展。通过数字图像相关（DIC）方法测量的机械场允许建立应变局部化，损伤演变和微观结构之间的关系，而发达的蚀刻方法（使表面具有自然纹理）使DIC在不遮盖微观结构的情况下达到可接受的分辨率是可行的。结果表明，裂纹萌生归因于大孔隙和/或先前成核裂纹的扩展所引起的应变局部化。裂纹沿着硬质夹杂物传播，但是硬质夹杂物的取向也对裂纹路径产生影响。