Hierarchical multi-scale microstructural evolution in an as-cast Al2CuCrFeNi2 complex concentrated alloy

The hierarchical evolution of the microstructure in an as-cast Al2CuCrFeNi2 alloy, across multiple length scales, was investigated by coupling scanning and transmission electron microscopy and atom probe tomography. This cast alloy undergoes a univariant eutectic dendritic solidification, which gives rise to a two-phase mixture of B2(e) (ordered BCC) and beta(e) (disordered BCC) phases. The B2(e) phase forms a continuous matrix with the beta(e), being the minor phase, having a rod-like morphology. The B2(e) phase is further decomposed into B2(f), Cu-plates, Cu-globules, and a small volume fraction of (Fe,Cr)-rich disordered beta(f2) regions. The beta(e) phase further decomposed into Cu/B2(s) core shell composite particles, where an ordered B2(s) shell surrounds a Cu-rich core. Most likely these Cu-rich cores act as heterogeneous nucleation sites for the B2(s) precipitates within the beta(f) phase. This complex multi-scale decomposition process results in an intricate mixture of ordered and disordered solid solution phases. (C) 2015 Elsevier Ltd. All rights reserved.