This study aims at examining the effect of tool rotational speed on the
microstructural and mechanical properties of friction stir welded joints of
AA6061 aluminum alloy, both pre- and post-heat treatment. The quality of the
joints was assessed initially through tensile, hardness, and charpy impact
tests, as well as microscopic observations. During the second stage, solid
solution heat treatments were conducted at 535°C, followed by aging on
additional specimens welded at identical speeds. The latter underwent hardness
tensile tests and microscopic examinations. A comprehensive assessment of the
outcomes from various tests validated the influence of metallurgical phenomena,
including recrystallization, precipitation, and structural defects on overall
resistance. The results showed an improvement in strength, ductility, and impact
energy was observed in the case of welding at high rotation speed (1400 rpm). At
the same speed, ductility almost doubled after post-weld heat treatment.
However, the treatment leads to a slight increase in strength and a decrease in
ductility and impact energy at low speeds.
