Microstructure and Mechanical Properties of Friction Stir Welded 5083 and 7075 Aluminum Alloys

Through microscopy, mechanical testing, and numerical modeling, the microstructure and mechanical performance of friction stir welded aluminum alloys 7075-T651 and 5083-H111 were characterized. In particular, the influence of the weld configuration, i.e., the locations of the 7075 and 5083 alloys alternately on the advancing and retreating sides, on material flow, microstructure, and mechanical properties was considered. Thermographic data in conjunction with a process simulation demonstrated that the weld configuration significantly impacts heat generation during friction stir welding. The microstructure in the stir zone was a clear visualization of the material flow and was characterized by a vortex-like structure with alternating bands of the alloys being joined. These bands differed in elemental content and grain size. The microstructure became more complex when greater heat generation (higher temperatures) occurred. The weld configuration strongly influenced the material flow, but did not impact the tensile properties (such as yield strength, tensile strength, and elongation). The configuration of 5083 on the advancing side and 7075 on the retreating side produced the most uniform material flow. The joint efficiencies of all tested welds were above 100%.