Microstructure, mechanical properties and corrosion resistance of Al6061/BN surface composite prepared by friction stir processing

In this research, the effect of boron nitride (BN) reinforcement particles on microstructure and mechanical properties of Al6061-T6 surface layer composites prepared by friction stir processing (FSP) were investigated. Microstructural changes of surface composites were examined by optical microscope (OM). Also, scanning electron microscope (SEM) was utilized to evaluate dispersion of reinforcement particles. The results illustrated that the BN reinforcement particles were uniformly dispersed in the nugget zone after 4 passes of FSP. It was also determined that the micro-hardness was enhanced from 97 Hv to 157 Hv due to the pining effect of hard BN reinforcement particles and reducing the grain size of processed zone from 312.65 μ m to 12.09 μ m. The results also indicated that increasing the number of FSP passes increased hardness, as well as the yield strength ( σ y ), tensile strength ( σ UTS ) and elongation (%E) of specimens. Corrosion resistance of Al6061/BN surface composite was examined by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. Results showed that Al6061/BN surface composite presented better corrosion behavior in comparison to Al6061-T6 and FSPed Al6061-T6 without BN reinforcement particles.