Microstructure, microchemistry and environmental cracking susceptibility of friction stir welded 2219-T87

The microstructure, the microchemistry and the environmental assisted cracking susceptibility was investigated for friction stir welded 2219-T87 plates. It was found that the coarsening of the Al2Cu intragranular precipitates occurring within the thermo-mechanically and the heat affected zones after friction stir welding correlates with a decrease in the hardness values. The regions with the lowest hardness are relatively narrow in size and are limited to the boundary between the thermo-mechanically affected zone and the nugget. The weld microzones exhibited a different microstructure but a similar environmental assisted cracking susceptibility. The environmental cracking susceptibility of the weld was generally low. The constant extension rate tensile tests were carried out in air and in a 3.5 wt.% NaCl solution. For samples tested transverse to the welding direction failure occurred within the thermo-mechanically affected zone–nugget boundary. The thermo-mechanically affected zone–nugget boundary was also the softer region of the weld. The corrosion immersion tests indicated an increased resistance to corrosion for the friction stir welded region as compared to the weld unaffected parent metal.