Study on Binary Phase of Al-15%Mg2Si Composite

Al-15wt%Mg2Si composite was prepared by an in-situ method. The phase components and content were analyzed qualitatively and quantitatively by XRD. The XRD pattern of Al-Mg-Si alloy was simulated by Reflex and the simulated result was compared with the XRD result. Lattice constants, thermodynamic parameter and elastic constant of Mg2Si phase and Mg17Al12 phase in Al-Mg2Si composite were investigated by first-principle calculations from CASTEP program based on density functional theory to compare the stability and mechanical properties. There are only a-Al phase and Mg2Si phase in Al-15wt%Mg2Si composite as shown in XRD result; and the mass fraction of Mg2Si phase is 14.9%. The differences of XRD indices with the same crystal plane (h k l) between simulation and test are fractional. Therefore, the simulated result by Reflex is reliable. Only alpha-Al phase and Mg2Si phase are formed in theory shown by simulation. The calculated heats of formation and cohesive energies show that Mg2Si phase is easy to form and the alloying ability is stronger. Mg2Si phase is more stable than Mg17Al12 phase. Elastic modulus (E), shear modulus (G), and bulk modulus (B) of Mg2Si phase is higher than that of Mg17Al12 phase. However, the friability of Mg2Si phase is higher and the plasticity is lower.