Microstructure Evolution and Performance Improvement of Hypereutectic Al–Mg(2)Si Metallic Composite with Ca or Sb

In this article, the modification effects on Al–Mg(2)Si before and after heat treatment were investigated with Ca, Sb, and (Ca + Sb). In comparison with single Ca or Sb, the samples with composition modifiers (Ca + Sb) had the optimal microstructure. The sample with a molar ratio for Ca-to-Sb of 1:1 obtained relatively higher properties, for which the Brinell hardness values before and after heat treatment were remarkably increased by 31.74% and 28.93% in comparison with bare alloy. According to differential scanning calorimetry analysis (DSC), it was found that the nucleation behavior of the primary Mg(2)Si phase could be significantly improved by using chemical modifiers. Some white particles were found to be embedded in the center of Mg(2)Si phases, which were deduced to be Ca(5)Sb(3) through X-ray diffraction (XRD) and field-emission scanning electron microscope (FESEM) analyses. Furthermore, Ca(5)Sb(3) articles possess a rather low mismatch degree with Mg(2)Si particles based on Phase Transformation Crystallography Lab software (PTCLab) calculation, meaning that the efficient nucleation capability of Ca(5)Sb(3) for Mg(2)Si particles could be estimated.