Intermetallic phase evolution of 7050 aluminum alloy during homogenization

Intermetallic phase evolution of 7050 aluminum alloy during homogenization was investigated in detail by optical microscopy, scanning electron microscopy, energy dispersive spectrometry, differential scanning calorimetry, electron probe micro-analysis and X-ray diffraction methods. The results show that severe dendritic segregation exists in as-cast alloy. The dissolvable intermetallic phases in as-cast alloy consist of equilibrium η (MgZn2) phase, Cu and Mg enriched non-equilibrium aluminides and Cu enriched non-equilibrium aluminides. During homogenization, Cu and Mg enriched non-equilibrium aluminides, Cu enriched non-equilibrium aluminides and η (MgZn2) phase gradually dissolve into matrix. Equilibrium S (Al2CuMg) intermetallic phase nucleates and grows along the grain boundaries, and it disappears completely after multi-step homogenization. The proper homogenization processing is 400 °C × 10 h + step470 °C × 24 h + step485 °C × 4 h, which is consistent with the results of homogenizing kinetic analysis.

► Evolution of intermetallic phase during homogenization was investigated.
► An optimal homogenization treatment of 7050 ingot was developed.
► The homogenization kinetic equation of 7050 alloy was established.