High-cycle and very-high-cycle fatigue behavior at 973 K of Ti-48Al-2Cr-2Nb alloy via crystal plasticity finite element method

The high-cycle fatigue and very-high-cycle fatigue behavior of Ti-48Al-2Cr-2Nb alloy at 973 K was investigated based on the crystal plasticity finite element method. The feasibility of the model was validated by contrasting the experimental and simulation results of tensile test at 973 K, the fatigue behavior was further analyzed and the fatigue life was predicted. The results indicate that the tensile fracture mode is a mixture of cleavage and intergranular fracture, whereas fatigue fracture exhibits a mixed mode of quasi-cleavage and intergranular fracture. At 973 K, the fatigue life of the alloy decreases with the increase of cyclic stress amplitude, and no distinct fatigue limit was observed. Under cyclic loading, Mises stress concentrates predominantly near grain boundaries adjacent to grains with significant deformation differences, while plastic strain localizes within grains exhibiting soft orientations. Geometrically necessary dislocations accumulate mainly near grain boundaries, with screw dislocation components playing a dominant role. A fatigue indicator parameter (FIP) based on cumulative plastic strain ( P _ac) was introduced. The P _ac accumulates rapidly near grain boundaries with large misorientations, and the predicted fatigue lives fall within a ±2.0 error band. High cyclic stress levels lead to large FIP, resulting in short predicted fatigue life.