Coupling of X-ray computed tomography and surface in situ analysis combined with digital image correlation method to study low cycle fatigue damage micromechanisms in lost foam casting A319 alloy

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.