Study of Material Flow and Mechanical Properties of Friction Stir Welded AA2024 with AA7075 Dissimilar Alloys using Top-Half-Threaded Pin Tool

Abstract

This research work was aimed at evaluating the material flow behavior and mechanical properties of dissimilar aluminum alloys (2024 and 7075) joints prepared by friction stir welding using a tool with top-half-threaded pin. Macro and microstructural study for material flow investigation was carried out. Whereas mechanical properties of welded joints are examined using tensile and micro-Vicker's hardness tests. Zeiss EVO 18 SEM was used for the fractographic study. Average grain sizes were determined at various weld regions. The effect of grain size with the hardness and strength has been discussed. The results demonstrate that the thread's location on the pin significantly affects the flow of the material. The area where the material has been severely plasticized and moved was located at the weld root. Hence welding root defects like void, pinhole, insufficient filling, etc. are avoided. The tensile strength of friction stir welded joint was 312.7 MPa, equivalent to the joint efficiency of 66.5 %. HIGHLIGHTS The threaded pin tool pushed the soft material downwards hence avoiding root defects. The onion ring structure formation has been observed The tool pin is responsible for creating two separate regions at weld line: Low flow region at the top and high flow region at central areas The maximum tensile strength obtain is 312.7 MPa and 66.5 % joint efficiency GRAPHICAL ABSTRACT