Microstructure, mechanical characteristics, and electrochemical behavior of the wide-area stir zone fabricated in Al5083 by friction stir processing with overlapping technique

Abstract

In the current study, a wide-area stir region was created in Al5083 aluminum alloy using multi-pass friction stir processing (FSP) with 50% pin overlapping. Microstructural investigations such as grain structure analysis and intermetallic particle (IMPs) distribution were carried out on processed alloys using optical and scanning electron microscopy (SEM). Recrystallized fine grains were developed after FSP due to the intense plastic straining and dynamic recrystallization. It was also identified that the grain refinement was uniform in the stir region of all overlapping passes, resulting in uniform hardness over the wide-area stir region. Three different types of IMPs, such as needle shape iron-based IMPs, round shape magnesium-based IMPs, and the very fine magnesium-based IMPs along the grain boundaries, were identified from the SEM analysis. The tensile test findings showed that the elongation improved drastically after overlapping FSP, while the hardness and tensile strength were found to be decreased due to high temperature thermal cycles. Electrochemical investigations revealed that the corrosion rate decreased after FSP due to the formation of uniform grain structure and dissolution of iron-based IMPs.