Materials Characterization | 2019
Microstructure and mechanical/electrochemical properties of friction stir butt welded joint of dissimilar aluminum and steel alloys
Abstract
Abstract The microstructure and mechanical/electrochemical properties of friction stir welded (FSWed) joints of two dissimilar alloys, 5052-H32 aluminum and dual-phase (DP) steel, are studied. The FSW joint is fabricated with an offset of the FSW tool towards the DP steel on the advancing side of the tool. In the stir zone (SZ), three distinct regions are observed: i) a top layer consisting of the aluminum matrix with scattered steel fragments, ii) a middle layer having a mixed lamellar structure of Fe Al solid solutions and intermetallic compounds (IMCs), and iii) a bottom layer consisting of the steel. IMCs are observed in the middle layer and at the interfaces between the aluminum and steel alloys. Very different hardness profiles are obtained in the three layers in the SZ. The electrochemical corrosion investigation reveals that the FSW joint exhibits a higher corrosion rate compared to the base materials due to the scattered steel fragments and the increase in martensite content and low-angle grain boundaries (LAGBs).