Effect of Thermomechanical Processing on Abnormal Grain Growth in Al-2195 Friction Stir Welds

Abnormal Grain Growth (AGG) has been observed in annealed, friction stir welded and solution heat treated Al-2195. Al-2195 friction stir welds were subjected to cold, hot and warm rolling to various percentage reductions perpendicular to the welding direction. The samples were then solution heat-treated to 510ºC and water quenched. Of all the samples, cold rolling to at-least 25 % reduction, followed by solution-heat treatment, provided the greatest reduction in abnormal grain growth. Neither hot rolling nor warm rolling yielded reduced or prevented AGG. Transmission Electron Microscopy (TEM) and grain orientation analysis of the as-welded; welded and 20% cold rolled; and welded, 20% cold rolled and grain initiated samples has shown the formation of high angle grain boundaries in grain initiated state. The effects of various thermo mechanical processing on the AGG in Al-2195 friction stir welds were analyzed and discussed.