Composition Optimization of the Hpdc Alsimgmncu Alloys Via 3d Structure Investigation at Nano-Scale

In this study, AlSiMgMnCu alloys with different Cu and Mg contents were processed by the high pressure die casting (HPDC) technics. The phase formation and their microstructure evolution are quantitatively studied by serial block-face scanning electron microscopy (SBFSEM) at nano-scale in three-dimensions (3D). Through analysis of their 3D microstructure, effects of the spatial distribution, volume fractions and 3D morphology of the intermetallic phases on the mechanical properties of the alloys are systematically discussed. It is found that, with higher Cu content and lower Mg content, the nucleation and growth of the θ phases in the alloys would have advantage over the Q phases. In contrast, with lower Cu content and higher Mg content, the nucleation and growth of the Q phases would have advantage over the θ phases. Additionally, the Cu atoms promote the homogeneous nucleation of the θ phases, while Mg atoms promote the continuous growth of the Q phases. The uniformly distributed fine θ-Al 2 Cu phase provides the highest contribution to the strengthening of the HPDC AlSiMgMnCu alloys. Finally, an optimized as-cast Al-10Si-0.2Mg-0.5Mn-0.6Cu alloy with ultimate tensile strength, yield strength and elongation of 330 MPa, 168 MPa and 10.2%, respectively, has been produced