Effect of stirring speed and time on microstructure and mechanical properties of Cast Al–Ti–Zr–B4C composite produced by stir casting

A new aluminum matrix composite reinforced with B4C particles was manufactured using different stirring speeds and time. Stirring speeds of 600 and 700 rpm and stirring time of 5, 10, and 15 minutes were chosen for casting the aluminum-B4C composites The effects of these parameters on the microstructure and mechanical properties of the produced composites were analyzed using reflected light microscopy (RLM), scanning electron microscopy (SEM and FESEM), image analysis, density measurement, and tensile test. Image analysis of the as-cast microstructures revealed that longer stirring speeds and time resulted in higher reinforcement content in the as-cast microstructure and consequently the sample under 700 rpm stirring speed with 15 min total stirring time had incorporated most of the added B4C particles. Interface characterization performed by FESEM showed that the added Ti and Zr had accumulated at the interface. Tensile test results revealed that higher stirring speed and longer stirring time resulted in the reduction of ultimate tensile strength and total elongation for 700 rpm stirring speed. It was concluded that a 700 rpm stirring speed with 15 min stirring time could produce a composite sample with the incorporation of most of the added particles distributed almost uniformly throughout the microstructure.