Study On Deformation Mechanism And Thermal Deforamtion Behavior Of High Strength Plastic TiMoZr Alloy

Compared with TRIP/TWIP(TRIP:Transformation induced plasticity;TWIP:Twinning induced plasticity)strainless steel,conventional structural titanium alloys exist significant shortcomings,such as low plasticity and poor work hardening behavior,etc.In orde to overcome these shortcomings,the TWIP Ti-12Mo-10Zr(wt.%)alloy was designed by d-electronic design method and the strategy of controlling electronic concentration(e/a).On one hand,digital image correlation(DIC),electron backscatter diffraction(EBSD)and transmission electron microscopy(TEM)were used to characterize the microstructure evolution of solution-treated samples and analyze the deformation mechanism;on the other hand,the Gleeble-3800 thermal simulation machine was used to test the thermal mechanical behavior of the alloy,and the microstructure evolution of the alloy was analyzed by optical microscopy and EBSD.The results show that solution-treated alloy has high yield strength(730MPa),high plasticity(ductility?32%)and excellent work hardening behavior(work hardening zones is about 360MPa).DIC experiments show high tolerance to local stress concentration,due to the formation of hierarchical {332}<113>deformation twinning during deformation.On one hand,the strength and work hardening properties of alloy are improved by dynamic Hall-Petch effect;on the other hand,the interaction of hierarchical deformation twinning and dislocation accommodated stress concentration,so that the alloy has high strength and plasticity.The hot compression results show that the true stress rise with the increase of strain rate,and decrease with the increase of temperature.Combined with the microstructure analysis,the main mechanism of microstructure evolution was dynamic recrystrallization at low strain rates(0.01s-1,0.I s-1),and dynamic recovery at high strain rates(1s-1,10s-1).The compression mechanical properties of the samples after the same strain rate thermal compression were studied at the room temperature,found that the yield strength increased with the increasing of hot compression temperature at double phase field(750?,800?),the yield strength decrease when temperature rising to 850?,and then yield strength reached maximum when temperature increased to 900?.At the same temperature(850?),the yield strength of samples after low strain rate(0.01s-1)compression is higher than that with high strain rate(1s-1).The constitutive equations of different phase fields are constructed under the peak stress.The optimal hot-working zones of the alloy under different strains hot processing graphs were 770??820?,0.01s-1?0.03s-1 and 880??900?,0.01s-1?0.1s-1.Through the analysis of optical microstructure and EBSD can be seen the grain deformation more severe in the same strain rate with the increase of temperature,the recrystallized grains began to appear at 800?,and the recrystallized grains are promiaryly distributed at grain boundaries,showing a typical discontinuous dynamic recrystallization phenomenon,and the recrystallized volume fraction gradually increased with the increase of temperature and the decrease of strain rate.There are 38 figures,6 tables and 90 references in this paper.