Investigation Of Alternating Bands In Friction Stir Welds Of Aluminum Alloys

Abstract

Friction stir welding (FSW) is a solid-state welding process that involves complex phenomena influenced by welding parameters such as feed and rotation speeds, as well as the tool geometry. These parameters condition the temperature cycles, which in turn affect the microstructure and mechanical properties of the weld. This study investigates the formation of alternating bands in FSW aluminium alloys, specifically focusing on the impact of welding parameters, tool geometry, and grain boundary characteristics. The alternating bands are identified as regions of contrasting grain structures, with differences observed in grain size and boundary orientation. High-angle (HA) boundaries, predominantly (111), and low-angle (LA) boundaries, predominantly (101), are found to alternate within the bands. Hardness tests, including Vickers and nano-indentation, show no significant variation in hardness between the alternating bands. The weld core consists of larger grains with HA joints and smaller grains with LA joints. The RS, on the other hand, contains equiaxed grains with HA joints and random orientations. Furthermore, the microstructure formed by HA grain boundaries exhibits a higher concentration of particles compared to the LA boundary areas. These findings provide new insights into the relationship between welding parameters, microstructure, and mechanical properties in friction stir welds.