In order to reduce manufacturing costs in the aerospace industry, it is desirable to expand the application of creep/ageforming to other applications apart from upper wing skins. Utilizing the ageforming technique for damage tolerant structures, particularly lower wing skins, requires alternative alloys that can be used in artificially aged tempers. Here, results are reported on the age forming behavior of three candidate alloys being considered for damage tolerant applications in an artificially aged temper, namely; 7475, 6056 and a new 2xxx series alloy, 2XU. An important further consideration, in this context, is the effect of the forming process on the microstructural evolution of the alloy during aging and its subsequent properties.

The Ageforming technique has been simulated in the laboratory by using constant strain, stress relaxation tests. The effect of forming temperature and initial stress on the level of stress relaxation, and hence age formability, has been investigated for each alloy on aging to a damage tolerant temper, in order to determine the dominant relaxation mechanism. The effect of the stress level on the microstructural evolution in each alloy has also been investigated by TEM. Of the alloys studied, the 2XU alloy exhibited the greater level of relaxation during tensile stress relaxation tests, but not during bend tests. This was attributed to the effect of the materials’ volume change during aging, which was positive for the Al-Cu alloy but negative for 7475 and negligible for 6056. It was also found that a similar level of stress relaxation occurred in each alloy when using a higher aging temperature, for the same equivalent aging time. In addition to the stress relaxation results, the microstructural studies showed that the precipitation behavior during aging in the 2XU alloy was very sensitive to the ageforming process, whereas in 6056 and 7475 there was little effect.