Microstructural and tribological properties of ultra fine grained hybrid composite produced by friction stir processing

Ultra fine grained (UFG) Al5083 based hybrid composite reinforced by SiC and MoS2 particles was prepared by Friction Stir Processing (FSP). A constant tool travel speed of 50 mm/min and different rotation speeds from 630 up to 1600 rpm were used. The microstructure of the Al based composite were investigated and compared to base metal and FSPed samples. It was found that although FSP resulted in decreasing the mean grain size of the base metal to about 2 µm, the addition of reinforcing particles in microstructure led to the more decrease in grain size of the alloy. An ultra fine grained hybrid composite with 500 nm grain size was obtained through rotation speed of 1250 rpm. Moreover, this hybrid composite showed the highest wear resistance and hardness in comparison to all samples due to the modification of microstructure and the addition of particles.