The kinetics of Fe-rich intermetallic formation in aluminium alloys: In situ observation

In situ synchrotron radiography of Fe-rich intermetallic formation was performed during the solidification of an Al–7.5Si–3.5Cu–0.8Fe (wt.%) alloy. Growth kinetics was quantified by segmenting the Fe-rich intermetallic phases and nucleation temperatures were determined by extrapolating to zero size. Fe-rich β-intermetallics nucleated between 550 and 570 °C, growing initially at an instantaneous tip velocity of 100 μm s−1, and slowing to 10 μm s−1 towards the end of growth. Final plate size was controlled by local Fe concentration and α-Al impingement.