3D morphological evolution and growth mechanism of proeutectic FeAl3 phases formed at Al/Fe interface under different cooling rates

The 3D morphologies and growth mechanisms of proeutectic FeAl3 at the Al/Fe interface under different cooling rates were studied by synchrotron X-ray tomography. With increasing cooling rate, FeAl3 crystals developed from faceted polygonal prism, plates with flat surface, thin ribbon-like with periodic undulating surface to non-faceted rods with radial dendrites in cross section, indicating a gradual interface growth mode transition from two-dimensional layer growth to continuous growth. At a higher cooling rate, twinning mechanism plays a leading role in the formation and growth of FeAl3. A link between the morphologies, twinning and crystallographic structure was established based on quantitative analyses on the 3D structures.