The Comparison of Yield and Fatigue Strength Dependence on Grain Size of Pure Ti Produced by Severe Plastic Deformation

摘要

Microstructure evolution and the mechanical behavior of UFG commercially pure Ti (grade 2) produced by ECAP were investigated, using the procedure designated as route B_c. Repetitive pressings of the same sample were performed to 4 passes at 683K. After four pass, recrystallized gains were uniformly distributed throughout the specimen with an average size of 0.4 μm. The fatigue limit σ_e of the pure Ti increased by 29% from 183.1 to 236.1 MPa after 4 pass ECAP. This result indicates that a significant improvement in high-cycle fatigue life can be achieved by applying ECAP on pure Ti. The standard Hall-Petch relation for yield stress and fatigue limit exhibit in the ECAPed Ti. The grain size dependence of k_y and k_e in the present Ti are 7.5 MPa √mm and 2.5 MPa √mm, respectively. The present Ti exhibits higher σ_o compared to σ_oe.