Abstract:Electromagnetic stir casting process of A357-SiC nanocomposite was discussed using the D-optimal design of experiment (DODOE) method. As the main objective, nine random experiments obtained by DX-7 software were performed. By this method, A357-SiC nanocomposites with 0.5, 1.0 and 1.5 wt.% SiC were fabricated at three different frequencies (10, 35 and 60 Hz) in the experimental stage. The microstructural evolution was characterized by scanning electron and optical microscopes, and the mechanical properties were investigated using hardness and room- temperature uniaxial tensile tests. The results showed that the homogeneous distribution of SiC nanoparticles leads to the microstructure evolution from dendritic to non-dendritic form and a reduction of size by 73.9%. Additionally, based on DODOE, F-values of 44.80 and 179.64 were achieved for yield stress (YS) and ultimate tensile strength (UTS), respectively, implying that the model is significant and the variables (SiC fraction and stirring frequency) were appropriately selected. The optimum values of the SiC fraction and stirring frequency were found to be 1.5 wt.% and 60 Hz, respectively. In this case, YS and UTS for A357-SiC nanocomposites were obtained to be 120 and 188 MPa (57.7% and 57.9 % increase compared with those of the as-cast sample), respectively.

Key words: A357 alloy; electromagnetic stir casting; SiC nanoparticles; mechanical properties; D-optimal design of experiments