Design And Preliminary Preparation Of Oxide Dispersion Strengthened Al-Sc-Zr Based Alloy

Aluminum alloys are widely used in aerospace and automobile manufacturing due to their good specific strength,low density,and corrosion resistance.However,under high-temperature conditions,the strengthening phases in aluminum alloys are extremely easy to coarsen and grow,resulting in severe softening of the Al matrix and a drastic decrease in mechanical properties.At present,the improvement of high-temperature properties of aluminum alloys is mainly focused on alloy composition optimization and subsequent processing processes,and the performance improvement brought by such approaches is getting weaker and weaker.In this paper,a novel oxide dispersion strengthens aluminum alloy is designed by combining first-principles calculations and experimental preparation,taking into account the role of TM and RE elements in forming high-temperature phases and nano-oxides in ODS alloys to improve high-temperature properties.The relative stability of the surface and interfacial structures of YAP and the segregation behavior of Sc,Zr,and Y elements at the Al grain boundaries were studied from thermodynamics.The oxide dispersion strengthen aluminum alloy with excellent high-temperature properties was preliminarily prepared by mechanical alloying and hot extrusion to achieve the re-solvation and re-precipitation of solute atoms.（1）Based on the thermodynamic defect model,YAP surface and interface equilibrium phase diagrams with respect to oxygen partial pressure and temperature are constructed to evaluate the thermodynamic stability of the surface and interface.The results show that the stability of the surface is highly sensitive to its stoichiometry and is influenced by temperature and oxygen partial pressure.Different terminal structures appear at different temperatures and oxygen partial pressures,but the ideal stoichiometric terminals always occupy a wider range of oxygen partial pressure.Based on the results of the surface phase diagram,the structure of the Al/YAP interface is predicted.The Al/YAP interface is also affected by temperature and oxygen partial pressure.The Al/YAP interface has a high bonding strength and a stable interfacial structure,which is related to the electronic interactions between the Al and O atoms at the interface.（2）The elemental segregation behaviors on eight typical low-sigma symmetric tilted grain boundaries were calculated,and Sc,Zr,and Y elements have strong segregation tendencies.The results show that the segregation of Sc,Zr,and Y elements on Al GBs are all stronger than the general main alloying elements,especially the Y element has the strongest segregation tendency at GBs,and all three elements have the strongest segregation at the GB atomic layer.（3）The oxide dispersion-reinforced aluminum alloy was preliminarily prepared by mechanical alloying and hot extrusion,with fine grains,Y-Zr-O,and Al₂O₃ particles in the matrix.Moreover,the severe plastic deformation and solid solution elements reduce the stacking fault energy of aluminum,which results in a large number of stacking faults in the matrix.The oxide particles and stacking faults together improve the high-temperature mechanical properties of the matrix,and the alloy still has a compressive strength of 178.5 MPa at 400°C with excellent heat resistance properties.