Microstructure of as-cast and homogenized 1973 aluminum alloy

The microstructure and the composition distribution of as-cast and homogenized 1973 alloy were studied by means of optical micrograph, scanning electron micrograph, X-ray diffractometry and DSC. The as-cast microstructure and the homogenizing temperatures of the alloy were determined. The results show that the as-cast microstructure is dendrite structure. It mainly consists of α-Al, MgZn₂ (η) phase and Al₂CuMg (S) phase, and Al₁₃(FeCu)₄ phases were also observed. The η phase (MgZn₂) dissolves aluminum and copper, and Al₂CuMg phase shows solubility of zinc. The proper homogenizing process of this alloy is at 470°C for 24 h. After homogenization, η phase and S phase dissolve almost into the matrix, leaving a small amount Al₁₃(FeCu)₄ phase and Al₇Cu₂Fe phases only. A large number of Al₃Zr phases with spheric shape were also observed, dispersing inside grains.