\ Effect of La inoculation on composition, content, granularity and mechanical properties of in-situ A1-30 wt%Mg2Si Composite

In this paper, the phase composition and content of Al-30 wt%Mg2Si composite prepared by in-situ process have been investigated; and the effect of different addition of La inoculation on microstructure, granularity and mechanical properties of Al-30%Mg2Si composite have been studied. Scanning electron microscope (SEM) and X-ray diffraction (XRD) images show that the phase composition and content of Al-30 wt%Mg2Si composite agree with pseudo-binary Al-Mg2Si phase diagram. The effect of La inoculation on microstructure indicates that La addition can change the morphology of primary Mg2Si particles and refine the particle size of primary Mg2Si. When the La addition reaches to 0.8 wt%, the refinement effect of Al-30%Mg2Si composite is the best. Similarly, the results reveal that La addition can effectively improve the ultimate tensile stress (UTS), breaking elongation (BE) and Vickers microhardness (VM) values. When La addition is over 0.8 wt%, primary Mg2Si particles become coarsening and mechanical properties decline. The crystal size was characterized by XRD and deduced by Cauchy and Gaussian approximation. The relationship between crystal size and UTS or VM can be described by Hall-Petch relation. The linear fitting degree of UTS is better.