The difference in material behavior between AA5083-O and AA6061-T6 in friction stir welding process

Abstract

Aluminum alloy has garnered attention as a means to reduce the weight of car frames, addressing environmental concerns. Traditional fusion welding faces limitations, particularly in addressing defects arising from fusion. Consequently, the adoption of friction stir welding (FSW), a solid-state joining technique, is on the rise. In welding, heat input plays a crucial role in determining weld quality. However, FSW involves friction heat and plastic heat, which cannot be directly measured. Researchers have utilized experimental measurements and numerical analysis models to address this issue. Recognizing the challenges in modeling this phenomenon, the concept of weld pitch, representing the ratio of tool rotational speed to welding speed, has been proposed as an indirect means to express heat input. FSW is intricately linked to the dynamic recrystallization process influenced by material flow, and this phenomenon can vary based on the composition of each material. Consequently, there is a need for research to explore material behavior differences within the FSW process. This study applies the same process window, designed using the weld pitch concept, to AA5083-O and AA6061-T6. A comparative analysis is conducted to elucidate the distinctions in their material behaviors. The experimental results reveal variations in welding conditions leading to tunnel defects in AA5083-O and AA6061-T6 under different speed settings. Furthermore, differences are observed in the welding conditions ensuring high tensile strength, along with variations in the materials' microhardness distributions. These findings confirm significant disparities in the properties of FSW weldments for each material, attributable to differences in the hardening types of individual aluminum alloys. It is suggested that these discrepancies in hardening types stem from variations in material behavior.