Material flow and mechanical behaviour of dissimilar AA2024-T3 and AA7075-T6 aluminium alloys friction stir welds

• Published in: Materials in engineering 2011-04, Vol.32 (4), p.2021-2027
• Main Authors: da Silva, A.A.M., Arruti, E., Janeiro, G., Aldanondo, E., Alvarez, P., Echeverria, A.
• Format: Article
• Language: English
• Subjects: A. Non-ferrous metals and alloys; Aluminum base alloys; Boundaries; D. Welding; Dissimilar materials; F. Microstructure; Friction stir welding; Grain size; Holes; Microstructure; Onions
• ISSN: 0261-3069
• DOI: 10.1016/j.matdes.2010.11.059

► High rotation speed yielded intense onion ring-like mixing pattern in the stir zone. ► Limited material mixing at low rotation speeds. ► Pin tool threaded profile plays an important role in material flow and mixing pattern. The scope of this investigation is to evaluate the effect of joining parameters on the mechanical properties, microstructural features and material flow of dissimilar aluminium alloys (3mm-thick AA2024-T3 and AA7075-T6 sheets) joints produced by friction stir welding. Mechanical performance has been investigated in terms of hardness and tensile testing. Material flow using the stop action technique has also been investigated in order to understand the main features of the mixing process. No onion ring formation has been observed; the boundary between both base materials at the stir zone is clearly delineated, i.e., no material mixing is observed. A non-stable rotational flow inside the threads has been identified due to the formation of a cavity on the rear of the pin. Microstructural observation has revealed the development of a recrystallised fine-grained stir zone, with two different grain sizes resulting from the two different base materials.