Fatigue Strength of Wire Arc Additive Manufactured Nano-Particle Enhanced AA7075 Material

The fatigue strength of wire arc additive manufactured (WAAM) nano-particle enhanced AA 7075 material was investigated. The material could be deposited without solidification cracks to form a slender wall; however, the fatigue strength was lower than AA 7075 produced by either additive cold spray deposition or rolling. Most of the fatigue cracks initiated from the surface or near-surface porosity. The microstructure of the additive manufactured AA 7075 consisted of fine and equiaxed grains, with an average grain size of 10.4 μm. SEM observation revealed agglomerated TiC clusters with sizes > 1 μm located along the grain boundaries. A method for estimating the equivalent defect-free S-N curve was proposed by using a √area parameter. It is suggested that the defect-free WAAM material would be comparable to that of solutionized cold spray deposited AA 7075.