Microstructure and Intermetallic Phase Evolution during the Homogenization of an Al–Zn–Mg–Cu–Zr–Nd Aluminum Alloy

Abstract

The intermetallic phase evolution during the homogenization of an Al–Zn–Mg–Cu–Zr alloy with Nd addition is investigated. Large amounts of the eutectic interdendritic acicular‐state η (MgZn2) phase, primary phase T (AlZnMgCu), Al8Cu4Nd, and Al7Cu2Fe exist at the grain boundaries of the as‐cast Al–Zn–Mg–Cu–Zr–Nd alloy. The homogenized intermetallic phase evolves as follows: the η phase dissolves into the α (Al) matrix, most of the T phase is dissolved in 16 h, and the remaining part of the T phase is transformed into the S phase (Al2CuMg) after 24 h. The stable Al8Cu4Nd phase in the alloy captures Cu atoms and inhibits the further generation of the S phase during homogenization. The addition of Nd decreases the fraction of the S phase, and only Al7Cu2Fe, Al8Cu4Nd, and Al2CuMg remain after homogenization for 24 h. Homogenization kinetics analysis suggests that the Al–Zn–Mg–Cu–Zr–Nd alloy is suitably homogenized at 470 °C 24 h−1.