Mechanical and metallurgical effects of in process cooling during friction stir welding of AA7075-T6 butt joints

This paper presents the results of a combined experimental and numerical investigation focused on the effects of an in process water cooling treatment aimed at improving the final quality of friction stir welded butt joints in terms of mechanical resistance and metallurgy of the processed material. Micro and macro observations, together with the evolution of an already developed finite element tool, have been used to analyze specimens obtained under different process conditions. Water cooling was found to enhance joint strength, reducing the material softening usually observed in the thermo-mechanically affected zone area, with no detrimental effect on nugget integrity. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.