Study On The Microstructure Law Of Pure Titanium TA1 Multi-pass Thermal Deformation

In this paper,pure titanium TA1 was used as the main research object.The Gleeble-3500 thermal simulation test machine was adopted to carry out multi-pass hot compression simulation experiments.The effects of three deformation parameters,holding temperature,deformation temperature and deformation on the multi-pass high temperature deformation of pure titanium TA1 were studied.Through the calculation and analysis of the stress-strain curve of multi-pass hot compression of pure titanium TA1,the variation law of flow stress and the softening law of secondary compression were obtained under different conditions of hot compression deformation.The microstructure of the hot-compression-deformed specimens was observed by metallographic and electron backscattering techniques.Furthermore,the effects of different hot-compression deformation conditions on the microstructure of pure titanium TA1 multi-pass hot deformation were studied.The following conclusions were drawn:(1)The flow stress during the multi-pass thermal deformation process of pure titanium TA1 is affected by the holding temperature,deformation temperature and shape variables.When the holding temperature is 900 °C,the flow stress is the smallest.When the holding temperature exceeds 900 °C,the higher the temperature,the smaller the flow stress.When the holding temperature is lower than 900 °C,the lower the temperature,the higher the flow stress.The influence of deformation temperature on multi-pass thermal deformation follows that the higher the deformation temperature,the smaller the flow stress.When the deformation path is the same,the larger the total shape deformation,the larger the flow stress of the multi-pass hot deformation.When the total shape deformation is constant,increasing the deformation path can effectively reduce the flow stress of a single pass.(2)The grain of the pure titanium TA1 is refined in the multi-pass hot compression process,and its mechanical properties and microstructure are both improved.The softening mechanism in the multi-pass hot compression process is mainly dynamic recovery,dynamic recrystallization assisted deformation.After the deformation,the microstructure mainly presents deformed and subgrain grains,while only a few recrystallized grains can be observed.The mechanism of recrystallization nucleation during multi-pass compression is mainly the nucleation of the grain boundary,and the sub-crystal rotation combined with the auxiliary nucleation,increasing the deformation temperature and the deformation can increase the proportion of recrystallized grains.The higher temperature,the larger deformation,with more recrystallization during thermal compression.(3)During the thermal deformation process of pure titanium TA1,the sliding actuation was influenced by temperature and deformation.Under high temperature and large deformation variations conditions,Smith factor was larger,which supported the sliding movement.(4)Static softening occurs during the interval of multi-pass hot compression deformation,and the softening rate increases with the increase of deformation temperature.When the temperature is the same,the larger the single-channel deformation,the better softening effect between passes.