The Effect of Binder Components and Powder to Binder Ratio on Rheological Properties of Mg-SiC Feed-stocks

Rheological characteristics of powder injection molding feedstocks play an important role in final properties of manufactured metal matrix composites. In this study, six formulations composed of magnesium and SiC powder (99:1 wt.%) and a specific binder were prepared to investigate the influence of binder composition, powder to binder ratio, time and temperature on rheological properties of the feedstock. The binder system contained Paraffin wax, Bees wax, and Stearic acid. Flow chracteristics of the compounds were investigated versus shera rate, time and temperature via rheological studies using a rotary rheometer. Finally, a heat treatment schedule was determined to effectively remove the binder from feedstocks. The resaults show that, Viscosity versus shear rate exhibited three different parts with different slopes for all of the studied feedstocks. The component including 2% stearic acid yielded newtonian behavior and increasing the amount of stearic acid up to 6 wt % contributed to the pseudoplastic behavior which is favorable from the view point of manufacturing intricate shapes. Addition of more than 6 wt % stearic acid to the feedstock increased the flow behavior index n and devastated rheological behavior of the feedstocks.