Effects of stirring parameters on the rheocast microstructure and mechanical properties of aluminum alloy ADC12

¹ Hasanuddin University, Department of Mechanical Engineering, Faculty of Engineering, Makassar, 90245 Indonesia
² Politeknik Negeri Ujung Pandang, Department of Mechanical Engineering, Makassar, 90245, Indonesia.

^* Corresponding author: syaharuddinrasyid@poliupg.ac.id

Abstract

In this study, effects of stirring time and stirring speed on the microstructure of semisolid rheocast (SSR) aluminum alloy ADC12 were examined. The research method was done by gravity casting using a metal mold. The aluminum ADC12 slurry is stirred by a mechanical stirrer (round rod stirrer) at 610OC with a variation of speed 0, 250, 300, 350 rpm for 0, 20, 40, 60 seconds. Furthermore, the aluminum slurry of ADC12 is poured on a metal mold with temperature 600OC. The microstructure characteristics were examined by direct observation using optical microscopy, secondary -Al phase dendrite arm spacing, shape factor, and Si eutectic phase were identified. The mechanical properties were investigated by hardness test and tensile test. A short period of stirring below the liquidus temperature to form a non-dendritic structure. The final morphology of the primary particles after a short period of stirring time has little impact as the stirring time increases. The optimal mechanical properties (hardness and tensile strength) were obtained at 20 seconds of stirring time and 300 rpm of stirring rate.