Effect of reinforcement amount, mold temperature, superheat, and mold thickness on fluidity of in-situ Al-Mg_2Si composites

In the present study, the effects of mold temperature, superheat, mold thickness, and Mg_2Si amount on the fluidity of the Al-Mg_2Si as-cast in-situ composites were investigated using the mathematical models. Composites with different amounts of Mg_2Si 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℃ to 200℃, superheat from 50℃ to 250℃, 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_2Si in the range from 15 wt.% to 25 wt.% lead to the lower fluidity of the composites. For example, when the mold temperature, superheat, and thickness are respectively 100℃, 150℃, 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_2Si, the morphology of the primary Mg_2Si becomes irregular and the size of primary Mg_2Si is increased. Moreover, the change of solidification mode from skin to pasty mode is the most noticeable microstructural effect on the fluidity.

Casting fluidity,viscosity,microstructure and tensile properties of aluminum matrix composites with different Mg_(2)Si contents

The effect of Mg_(2)Si amount on the properties of Al-Mg_(2)Si as-cast composites was investigated in this study.Composites with different amounts of Mg_(2)Si(15 wt%,20 wt%and 25 wt%)were fabricated,and the fluidity,viscosity,porosity formation and tensile properties were then analyzed.In addition,optical microscope and scanning electron microscope were used for micros tructural studies and fractography.The results reveal that with the amount of Mg_(2)Si increasing,the morphology of the primary Mg_(2)Si becomes irregular,the size of primary Mg_(2)Si increases,fluidity decreases,viscosity increases,and porosity amount increases.The reason for the higher amounts of porosities is the lower fluidity and higher viscosity.In addition,Al-15%Mg_(2)Si shows better tensile properties and higher quality index compared to other composites.Furthermore,the fracture surface of the composite with lower Mg_(2)Si amount reveals more ductile mode than those with higher Mg_(2)Si amount.