Abstract: The microscopic mechanism of crack propagation in TC4-DT titanium alloy was discussed by fracture analysis. Specifically speaking, the analysis of microscopic mechanism of crack propagation corresponding to the TC4-DT titanium alloy with diverse microstructures was conducted from the formation of microcracks, fatigue crack propagation of initial stage, near-threshold zone and the steady-state zone. The analysis results indicated that the cyclic loading caused the rough fracture surface and the dislocation accumulation at the phase interface during plastic deformation to induce crack initiation for the lamellar structure. The cracks in the equiaxed microstructure were primarily derived from the fracture surface generated by small grain deformation process. In the near-threshold area, the dislocations accumulation during the deformation of the equiaxed grains gave rise to the cracks along the grain boundary, accelerating the crack propagation. The size effect of the secondary α phase in double-layer structure also sped up the crack propagation. In the steady-state extension zone, the fracture surface transitions from the zigzag fracture mode of the first stage to the striation fracture mode of the second stage, presenting the plastic strip fracture mechanism.
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2019, Vol. 33 
