Microstructure evolution and high-temperature strengthening-toughening mechanism of the Al-10Ce alloy deposited by laser-directed energy deposition

The effects of laser-directed energy deposition (LDED) and casting on the microstructure evolution of an Al-10Ce alloy were studied. The results showed that the high cooling rate and the strong temperature gradient of the LDED inhibited the formation of the primary Al₁₁Ce₃ phase and promoted the refinement of the eutectic Al₁₁Ce₃ phase. At 300 °C, the LDED sample still exhibited excellent mechanical properties with the tensile strength, the yield strength and the elongation of 103 MPa, 79 MPa and 29.1%, which were better than those of the cast sample of 75 MPa, 46 MPa and 24.6%, respectively. Further, the high-temperature strengthening-toughening mechanism of the Al-10Ce alloy produced by LDED were mainly attributed to: (1) The refinement of the Al₁₁Ce₃ phase was conducive to the formation of high-density dislocations during deformation; (2) The elimination of the primary phase and the passivation of the phase interface reduced the stress concentration; (3) At high temperature, the dislocation recovery and the decomposition into stacking faults coexisted, which promoted the plasticity improvement and the strength maintenance.