Elevated temperature microstructural stability in Al-7Cu-0.5Mn-0.2Zr alloys through Ce addition: Enhanced coherent interfacial stability of cu-rich '/-Al interface

In this study, Ce was added into Al-Cu-Mn-Zr alloys to investigate the effect of Ce atoms on theta' precipitates via HAADF-STEM (high-angle annular dark-field scanning transmission electron microscopy). The results showed that Ce atoms could enter the lattice of theta' precipitates to occupy the internal Cu atom sites. Moreover, the interfacial stability of Cu-rich theta'/alpha-Al matrix with Ce addition was also estimated by DFT (Density Functional Theory). The Cu-rich theta' precipitates with Ce occupation demonstrated a lower interface energy (0.27 J/m2) than that of theta' precipitates without Ce occupation (0.45 J/m2). In other words, Ce atoms could stabilize the inter-mediate metastable Cu-rich theta' precipitates and therefore enhance the coarsening resistance of theta' precipitates at elevated temperatures. The addition of 0.3Ce can enhance the aspect ratio and decrease the number density of theta' precipitates in the Al-7Cu-0.5Mn-0.2Zr alloy in the T7 state. As a result, the elevated temperature microstructural stability of theta' in Al-7Cu-0.5Mn-0.2Zr alloys with Ce addition can be improved via enhancing coherent interfacial stability of the Cu-rich theta'/alpha-Al interface.