Micro-alloying effect of Er and Zr on microstructural evolution and yield strength of Al-3Cu (wt.%) binary alloys

In the present study, a textbook binary model alloy Al-3Cu (wt.%) was chosen as base alloy and micro-alloying effect with different Er and Zr contents was examined. A two-steps homogenization regime was optimized as 450 degrees C/3 h + 490 degrees C/20 h. The precipitation and recrystallization behaviors are characterized using transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) techniques. It is found that recrystallization behavior at 500 degrees C was fully inhibited with co-additions of Er and Zr. Heterogeneous nucleation of refined theta' phases on core-shell Al-3(Er,Zr) dispersoids was firstly observed. In addition, strengthening contribution from the L1(2) dispersoids and precipitates were detailed discussed. The refinement of theta' to 96.6 nm (average diameter) in Al-Cu-Er-Zr can compensate the reduction of nucleation driving force due to the loss of Cu solute atoms resulted from Al8Cu4Er primary phase.