The structural stability, mechanical properties and stacking fault energy of Al3Zr precipitates in Al-Cu-Zr alloys: HRTEM observations and first-principles calculations

Al3Zr precipitates in Al-Cu-Zr alloys are investigated using high-resolution transmission electron microscopy. The results show that Cu can effectively stabilize the L12 phase and which may originate from Ref. 〈110〉(001) slip systems activated by Cu, that is in good agreement with our first-principles predictions. Moreover, theoretical calculations show that Zn and Ag has same effect as Cu. The ductility can be improved for stabilized L12 phase with Cu, Zn and Ag based on the Pugh's criterion. Rice and Zhou-Carlsson-Thomson criterions are used to reveal the brittle/ductile mechanism using stacking fault energy. Finally, the electronic density of states show that the brittleness of D023-Al3Zr is mainly due to the strong covalent bonding between Al and Zr atoms, and the improved ductility is mainly due to the weakened Zr 4d and Al 3p covalent interactions with the addition of Cu, Zn and Ag.