Micro-compression Behavior And Microstructural Evolution In Pure Titanium And Titanium Alloy

As modern science and technology development is rapid, product miniaturization has become the important factors that affect in dustrial development, the micro manufacturing technology has become more and more important. In recent years, a new rise microfabrication technology-micro plastic forming has been applied to the industrial production. Micro plastic forming has the advantages of high production efficiency、 high material utilization、low cost、no pollution and net forming, besides forming parts also has good mechanical properties. But traditional materials for macro plastic forming and deformation behaviors analysis methods are no longer applicable, so the development of new materials and study of micro plastic forming mechanism is imperative. The titanium and titanium alloy is a new kind of material with good comprehensive performance, and it can be applied to various fields, so if we can combine these two aspects, it will be beneficial for micro forming and the application of titanium alloy.Firstly in this paper we can get five kinds grain size of TA2 pure titanium and four kinds typical microstructure of TC4 titanium alloy through the heat treatment process, and at room temperature and high temperature respectively do the micro compression experiment. Then we make the analysis of titanium and titanium alloy micro plastic deformation behavior of the compression process the analytical under different parameters interaction of sample size、grain size、microstructure、strain rate and deformation temperature,and we also make the analysis of the influence of sample parameters and process parameters on material flow stress. So we can reveal the organization evolution law in micro compression process of titanium and titanium alloy, then provide reference for the micro forming of titanium and titanium alloy materials.It shows that in the TA2 pure titanium micro compression experiment: the flow stress decreases with the decrease of the sample size, and the deformation area organization distortion is more serious with the smaller sample size; the flow stress increases with the reduction of grain size, but at room temperature compression abnormal phenomenon occurs, that is when the grain size is too large, the flow stress increases. When we do micro compression under the high temperature, the smaller the grain size, the more recrystallization nucleation number there will be; At room temperature the strain rate sensitivity of deformation materials is lower than high temperature. At high temperature, with the decrease of the strain rate, the flow stress has a tendency to reduce. When the pure titanium is under high temperature compressed, with the decrease of the strain rate, the recrystallization of the microstructure in more fully. The flow stress will be reduced with the increase of deformation temperature. With the increase of deformation temperature, the number of recrystallization grain increases and the size of recrystallization grain increases; When the TA2 pure titanium is under room temperature micro compression, grain size, the smaller the sample size, the greater rough the sample surface is, and the drum is more uneven.The result of TC4 titanium alloy micro compression experiment shows that: the flow stress at room temperature and high temperature decreases with the decrease of the sample size, and the sample size has a little influence on the evolution of the organization; mechanical properties of different microstructure is different, widmanstatten structure has the highest strength, but low plasticity; and the plasticity of shaft organizations is the best, but the strength is slightly lower. At high temperature, shaft organization recrystallization nucleation occurs mainly in the alpha phase grain boundary, while the top organizations and widmanstatten structure recrystallization nucleation are mainly distributed in alpha bundle junction, and large angle grain boundaries are mainly distributed in the recrystallization nucleation area; with the decrease of the strain rate, the flow stress are reduced, and just at room temperature the change of the flow stress is lesser, and shows the low sensitivity of flow stress. And it is under high temperature micro compressed, the strain rate decreases, deformation time increases, dynamic recrystallization in the process of deformation is fully done, the grains grow up. In addition, with the decrease of the strain rate, the content of small angle grain boundary decreased; the higher the deformation temperature, the lower the flow stress becomes. With the increase of deformation temperature, the small angle grain boundary in the microstructure reduces, when the deformation temperature varies from 750℃ to 800 ℃, the recrystallization occurs, as a further rise in the temperature of deformation, the recrystal0 lization grain grows; At room temperature,fracture of the different microstructure of TC4 titanium alloy are quasi-cleavage fracture.