In-situ X-ray radiography of twinned crystal growth of primary Al13Fe4

A team of Oxford Materials researchers from the Processing of Advanced Materials Group collaborated with Imperial College during this investigation to study faceted growth of primary AlFe4 intermetallic compounds using in-situ X-ray radiography in a solidifying Al-3Fe alloy.

The paper, published in Scripta Materialia, describes how the team observed microscopic twins in the growing intermetallics, the presence of which were confirmed by post-solidification electron backscatter diffraction.  

A twin plane re-entrant growth mechanism was suggested, where repeated formation of re-entrant corners facilitated crystal growth along a preferential direction, forming elongated plates.  In contrast, for intermetallics where this preferential growth was constrained by surrounding crystals, formation of layered twins perpendicular to the preferential direction was promoted and led to lower aspect ratios, known to be less deleterious to tensile properties.