Effect of Annealing and Crack Orientation on Fatigue Crack Propagation of Ti64 Alloy Fabricated by Direct Energy Deposition Process

Abstract

Effects of annealing condition and crack orientation on fatigue crack propagation (FCP) behavior of DED (direct energy deposition)-processed Ti-6Al-4V (Ti64) specimens were studied. It was found that the FCP resistance of Ti64 increased significantly with annealing, particularly above beta transus temperature, due to the microstructural coarsening inducing less damage accumulation at the tip of crack. The FCP behavior of as-built and as-annealed DED Ti64 specimens was isotropic with crack direction either parallel or perpendicular to building direction. The detailed micrographic and fractographic analyses on FCP-tested specimens suggested that the presence of largely elongated beta grain boundaries did not affect the advance of crack.