Effect of La/Nd ratio on microstructure and tensile properties of AZ91-RE alloys

The effect of La/Nd ratio on the microstructure and tensile properties of AZ91-RE alloys was studied. Typical characterization was performed to analyze the volume fraction, mean nearest neighbor distance (NND), and number density of the secondary phases. First-principles calculations were employed to determine the formation enthalpy, mechanical and thermodynamics properties of the secondary phases. The results demonstrate that the alloy with a mass fraction ratio of La to Nd (wLa/wNd) of 3:2 exhibits the finest average grain size, the smallest mean NND, and the highest total number density of secondary phases. The calculations indicate that the formation of Al11La3 and Al2Nd is energetically favorable. Furthermore, Al11La3 and Al2La display significantly superior deformation resistance, shear deformation resistance, solid stiffness and thermal stability compared to other secondary phases. Therefore, increasing the content of Al11La3 and Al2La phases contributes to improving the mechanical properties of AZ91-RE alloy.