EXPERIMENTAL INVESTIGATIONS ON THE IMC IN FRICTION STIR WELDED AA7075 ALUMINUM JOINTS WITH COPPER INSERTS
Keywords:
FSW, AA7075, Copper Insert, IMC, Mechanical properties, Macrostructures , SEMAbstract
Friction Stir Welding (FSW) is an innovative and promising solid state joining process invented by The Welding Institute (TWI). FSW can arguably be said to represent one of the most significant developments in metal joining technology over the last two decades. The intense plastic deformations and temperature fluctuations generated by the rotating and traversing tool in FSW have a significant impact on the micro structural modifications in the weld zone and thereby on the mechanical properties of the welded joint. Experiments were conducted on 6 mm thick AA7075, commercially available aluminum plates, widely used in structural fabrication of critical components in aerospace, defence and military applications, where the weld strength is expected to be very near to the parent metal strength. The plates were joined by FSW on both sides, with and without a thin layer of copper insert in-between the two aluminium plates. Mechanical and metallurgical characterization of the welded joints shows superior strength in copper inserted joints as compared to the joints without intermediate copper layer. Influence of the newly formed Inter Metallic Compound (IMC) with copper particles dispersed in a solid solution of aluminium matrix enhances the joint strength. High hardness with fine grains of the IMC in weld nugget improves the tensile strength of the joint.
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