INFLUENCE OF ENERGY INPUT IN FRICTION STIR WELDING ON STRUCTURE EVOLUTION AND MECHANICAL BEHAVIOUR OF 304L AUSTENITIC STAINLESS STEEL

摘要

Stainless steeis are an important class of engineering materiais widely used in a variety of industries and environments. These materiais, which are usually considered difficult to weld by conventional fusion welding processes, have demonstrated outstanding performance when joined by friction stir welding (FSW), a solid-state joining process. FSW input energy regulates the magnitude of the thermal cycle and the intensity of deformation taking place during the process, and it can be controlled by the welding parameters, affecting the grain features and consequently the mechanical properties of the joints. Nevertheless, there remains a lack of knowledge abc-ut the microstrutural evolution of these alloys during FSW, and its correlation with weld energy input and their respective mechanical properties, particularly for austenitic stainless steeis. The objective of this article is to establish the microstructure/properties/weld energy input relationships of FS-welds with different welding parameters. Microstructural investigation of the FS-welds showed similar weld zone formation, but presented specific grain features, according to weld zone and energy input. The most significant effect was observed in the SZ. The increase of energy input led to formation of coarse recrystallized grains, a remarkable grain growth and sigma phase formation.