(a) Light microscopy observation of the radial view of the A_CCA after drawing until a diameter of 1 mm. In inset is the corresponding thresholded picture. (b) SEM picture of the 1 mm diameter ACCA wire after an annealing treatment at 400 °C for 6 h (cross sectional view). In inset, atomic concentration profile of Al and Cu element through the interface. Al₂Cu, AlCu and Al₄Cu₉ can be well-identified [21].