Study on Low-cycle Fatigue Performance of Pure Titanium with Bimodal Structure:Experiment and Simulation
The bimodal-grained distribution was introduced into the microstructure of pure titanium through cryo-rolling combined with annealing heat treatment.The tensile properties and low-cycle fatigue properties of bimodal pure titanium(BM-Ti)were systematically studied.Compared to the original coarse-grained pure titanium(CG-Ti)and ultra-fine grained pure titanium(UFG-Ti),BM-Ti exhibited excellent strength-ductility matching properties with high yield strength(634.4 MPa)and high uniform elongation(7.2％).The results of low-cycle fatigue experiments indicate that the bimodal structure cannot effectively improve the fatigue life of pure titanium.During the cycling process,the coarse-grained area of BM-Ti bore most of the plastic deformation,and a large number of dislocations accumulated within coarse grains,gradually dividing the grains and leading to the refinement of coarse grains.The low-cycle fatigue behavior of BM-Ti was simulated by crystal plasticity finite element method,and accumulated plastic strain was introduced to evaluate the damage during the fatigue process.It was found that the heterogeneous interface of BM-Ti is more prone to fatigue crack initiation due to strain incompatibility.
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