Yield Strength and Residual Stress Measurements on Friction-Stir-Welded Aluminum Alloys

摘要

Friction-stir welding is a relatively new joining technology that has great potential for the aerospace industry. Tonuse friction-stir welding tomanufacture an airworthy and damage-tolerant structure, themechanical behaviormustnbe fully understood. This paper presents the experimental results in which the local yield strength and the residualnstress profile for friction-stir-welded AA2024-T3, AA7075-T6, and AA6013-T4 were measured. X-ray diffractionnwas used tomeasure the residual stresses. The residual stress profiles in all three alloys exhibited high tensile stressesnin the center region of the weld. Around the weld the stress levels were reduced to either zero or low-magnitudencompressive stresses. Both AA2024-T3 and AA7075-T6 show comparable residual stress profiles, whereas AA6013-nT4 exhibits lower-magnitude residual stresses. Digital imaging correlation was used to measure the local yieldnstrength in all three alloys with and without welds. The yield strength profiles obtained with this new technologynmatched perfectly with the corresponding hardness profiles of the welds. A relation was found between the yieldnstrength profiles and the residual stress profiles, which resulted in understanding of how the appearance of thenresidual stress profiles is determined by the yield strength profile.