Study of the Microstructure and Crack Evolution Behavior of Al-5Fe-1.5Er Alloy

In this work, the microstructure of Al-5Fe-1.5Er alloy was characterized and analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) techniques. The effect of microstructure on the behavior of crack initiation and propagation was investigated using in situ tensile testing. The results showed that when 1.5 wt.% Er was added in the Al-5Fe alloy, the microstructure consisted of α-Al matrix, Al(3)Fe, Al(4)Er, and Al(3)Fe + Al(4)Er eutectic phases. The twin structure of Al(3)Fe phase was observed, and the twin plane was {001}. Moreover, a continuous concave and convex interface structure of Al(4)Er was observed. Furthermore, Al(3)Fe was in the form of a sheet with a clear gap inside. In situ tensile tests of the alloy at room temperature showed that the crack initiation mainly occurred in the Al(3)Fe phase, and that the crack propagation modes included intergranular and trans-granular expansions. The crack trans-granular expansion was due to the strong binding between Al(4)Er phases and surrounding organization, whereas the continuous concave and convex interface structure of Al(4)Er provided a significant meshing effect on the matrix and the eutectic structure.