Phase transformation and thermal stability of the laser powder bed fused high-strength and heat-resistant Al–Ce–Mg alloy

The coarsening of strengthening phases, phase transformations, and interface stability between these phases and the matrix play a crucial role in determining the strength, ductility, and heat resistance of aluminum alloys fabricated through additive manufacturing (AM). In this study, a heat exposure experiment at 400 °C for 1 h was conducted on the laser powder bed fused Al–Ce–Mg alloy. A comprehensive analysis of the microstructural evolution, phase composition, interfacial bonding strength, and mechanical properties before and after heat exposure was performed using synchrotron X-ray diffraction techniques, first-principles calculations, transmission electron microscopy, and mechanical testing. For the first time, a phase transformation from Al₁₁Ce₃ to Al₄Ce was discovered. Some semi-coherent relationships of [301]_Al11Ce3//[011]_Al, (060)_Al11Ce3//(00)_Al were transformed into coherent relationships of [001]_Al4Ce//[001]_Al, (200)_Al4Ce//(00)_Al, and the interfacial energy was reduced by 4.385 J m⁻². In-situ Al₁₁Ce₃ nano-networks after heat exposure were retained and Al₄Ce nanoparticles contribute to the thermal stability of the alloy by hindering dislocation motion and grain coarsening. The strength of the heat exposure alloy reached up to 416 MPa, which is about 95 % of the strength of the as-fabricated state and the elongation increased from 9.3 % to 13.8 %. These results provide a new approach for the design of high strength-ductility synergy and heat-resistant aluminum alloys via AM.