3-D morphology and growth mechanism of primary Al6Mn intermetallic compound in directionally solidified Al-3at.%Mn alloy

► 3-D morphology of Al6Mn exhibits hollow, distorted polyhedron with concaves. ► Final shape of Al6Mn depends on crystal structure and external growth environment. ► The growth of Al6Mn faceted phase is dominated by the screw-dislocation mechanism. ► A stacking structure is formed by repeating nucleation on concave surfaces.