Effect of reinforcement amount, mold temperature, superheat, and mold thickness on fluidity of in-situ Al-Mg2Si composites

In the present study, the effects of mold temperature, superheat, mold thickness, and Mg 2 Si amount on the fluidity of the Al-Mg 2 Si as-cast in-situ composites were investigated using the mathematical models. Composites with different amounts of Mg 2 Si were fabricated, and the fluidity and microstructure of each were then analyzed. For this purpose, the experiments were designed using a central composite rotatable design, and the relationship between parameters and fluidity were developed using the response surface method. In addition, optical and scanning electron microscopes were used for microstructural observation. The ANOVA shows that the mathematical models can predict the fluidity accurately. The results show that by increasing the mold temperature from 25 °C to 200 °C, superheat from 50 °C to 250 °C, and thickness from 3 mm to 12 mm, the fluidity of the composites decreases, where the mold thickness is more effective than other factors. In addition, the higher amounts of Mg 2 Si in the range from 15wt.% to 25wt.% lead to the lower fluidity of the composites. For example, when the mold temperature, superheat, and thickness are respectively 100 °C, 150 °C, and 7 mm, the fluidity length is changed in the range of 11.9 cm to 15.3 cm. By increasing the amount of Mg 2 Si, the morphology of the primary Mg 2 Si becomes irregular and the size of primary Mg 2 Si is increased. Moreover, the change of solidification mode from skin to pasty mode is the most noticeable microstructural effect on the fluidity.