The effect of process parameters on microstructural characteristics of AZ91/SiO2 composite fabricated by FSP

Process parameters are one of the major factors in friction stir processing. Therefore, the effects of these parameters were investigated in fabrication of AZ91/SiO2 composite. By keeping the rotational speed at 1250 rpm, three traverse speeds (20, 40, 63 mm/min) were selected on 8 mm thick AZ91 magnesium alloy. The prepared grove contained 8% volume fraction nano-SiO2 powder. Microstructural properties were investigated by means of optical microscopy (OM) and scanning electron microscopy (SEM). Results show that by increasing the traverse speed, grain size decreased significantly and hardness rose. Maximum amount of hardness achieved in this experiment was 124 HV and the minimum grain size was 8 μm. Also tensile properties of the specimen produced in one, two and three passes were investigated by standard tensile test. Results show that FSP improved the tensile characteristics of the as cast AZ91 alloy significantly.