Microstructure And Property Of Commercially Pure Titanium Processed By ECAP And Rotary Swaging At Room Temperature

So far, non-ferrous metal titanium is thought to be the most appropriate biomedical metal materials. In the present paper, pure Ti was successfully processed by Equal channel angular pressing(ECAP) up to 2 passes with a die of 135° at room temperature and Rotary Swaging to different reduction. Advanced characterizations and measurement techniques such as transmission electron microscopy(TEM), scanning electron microscopy(SEM), isothermal simulation and tensile test, were employed to investigate the microstructural evolution, mechanical properties of CP-Ti after ECAP and Rotary Swaging at room temperature and deformation behaviors of UFG Ti. The main results of the research are as follows:(1)The original grains was elongated, fragmented, significantly enhanced, and uneven deformed after 2 passes of ECAP. Then it is found that the grain size and micro-structure was more tiny and even than the ECAP deformation structure the later rotary forging processing. Besides, it indicates that structure inhomogeneity was improved after rotary forging processing, with the study of the hardness testing of sample cross section. Meanwhile, after ECAP and Rotary forging composite refining, the mechanics performance test reveals that the strength of CP Ti was significantly increased to meet the strength requirement of CP Ti within the biomedical field.(2)At the same time, It was found that the dislocation density of the micro-structure had decreased, tensile strength had declined and plasticity had increased gradually, with the increase of the annealing temperature. The recovery mainly occurred within deformed microstructure under 400℃. On the contrary, the recrystallization mainly occurred within deformed microstructure over 400℃.(3)Isothermal compression test was done on a Gleeble-3500 thermal simulation testing machine at strain rate ranging from 10-5 s-1 to 100 s-1, with deformation temperature from 298 K to 723 K. This investigation indicates that the flow stress curve had been obviously divided into three stages: work hardening stage, transition stage, as well as steady flow stage. Flow stress is much more sensitive to the change of deformation temperature and strain rate. Additionally, the change of strain rate and deformation temperature on flow stress is more significant, and the effect of deformation temperature on flow stress is greater. The study revealed that with the strain rate decreasing or the deformation temperature increasing, the value m is higher. The value of ST first increased then decreased at the same strain rate. Before the true strain is 0.1, the influence of deformation temperature on flow stress is greater; after the true strain is 0.1, the influence of deformation temperature gradually weakened.