Corrosion properties and mechanisms of friction stir lap welded TiB2/2024 aluminum matrix composite joint

The corrosion properties and mechanisms of friction stir lap welded (FSLWed) TiB2/2024 aluminum matrix composite joint immersed in 3.5 wt.% NaCl solution were deeply investigated. Electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and high resolution TEM (HRTEM) were conducted to characterize the microstructural evolution of various zones across the joint cross-section. The appearance and penetration depth of the etched surfaces were observed by scanning electron microscopy (SEM). The elements on the etched surface were analyzed by EPMA. Results show that the corrosion properties of the 600/200 (rotational speed 600 r/min, travelling speed 200 mm/min) joint are higher than those of the 400/200 joint. It is noted that the corrosion properties of the stir zone (SZ) are higher than those of base material (BM) and heat affected zone (HAZ) based on the open circuit potential (OCP), the corrosion current icorr, the impedance Rcorr and the corroded appearance after immersion corrosion regardless of the welding parameters.