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, Al₃Fe, Al₄Er, and Al₃Fe + Al₄Er eutectic phases. The twin structure of Al₃Fe phase was observed, and the twin plane was {001}. Moreover, a continuous concave and convex interface structure of Al₄Er was observed. Furthermore, Al₃Fe 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 Al₃Fe 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 Al₄Er phases and surrounding organization, whereas the continuous concave and convex interface structure of Al₄Er provided a significant meshing effect on the matrix and the eutectic structure.