Figure 6

Microstructure of Al–Fe–Cu alloy semisolid heating under different temperatures and times (unetched). (a) Holding 30 min at 610 °C, there are many circular Al₂Cu particles within the grains (from the liquid pools in the intra-grains) and thin the grain boundaries as well thick the re-solidified zones including Al₂Cu and Al₇Cu₂Fe mixtures (Cu-rich zone); (b) holding 30 min at 630 °C; (c) holding 30 min at 640 °C, the rounded Al₂Cu granules within the grains reduce and diminish, the grain boundaries broaden and the reticulations increase and the pinnates decrease in the re-solidified zones; (d) holding 5 min at 630 °C, there are retiform Cu-rich zone between the grains and rounded white Al₂Cu particles in the intra-grains; (e) holding 15 min at 630 °C, the distribution of shorter and sparser AlFe phases results in more circular grains; (f) holding 60 min at 630 °C, upper right, the grains are completely surrounded by the liquid, forming rounded grains and occurring grains join. Lower left, the liquid is separated by AlFe phases, resulting in irregular grains; (g) holding 5 min at 640 °C (Keller etched), the white Al₂Cu granules in the intra-grains, the white coppery compounds boundaries and retiform re-solidified zone between the grains; (h) holding 30 min at 610 °C, the skeleton Al₇Cu₂Fe etc. cupriferous compounds on the grain boundary; (i) holding for 20 min at 630 °C, the grain boundaries with skeleton cupriferous intermetallic and the re-solidified zone with the retiform Al₂Cu and the penniform Al₇Cu₂Fe mixture; (j) holding 60 min at 640 °C, the retiform Al₂Cu mixture on the re-solidified zone between the grains and AlFe phase, and showed broken AlFe phases.