Study On Plastic Mechanism Of TB6 Titanium Alloy At Room Temperature

TB6 is a metastable beta titanium alloy owing to their high specific strength,excellent fracture toughness, good creep and corrosion resistance, titanium alloys have been used widely in many fields such as aerospace, biomedical and sporting industries.TB6 titanium performance depends largely on the phase composition and microstructure which influenced by heat treatment process and the deformation mode.The microstructure evolution and mechanical properties of TB6 alloy during solution treatment, aging,pre-deformation and cooling rate have been studied by optical microscope(OM), transmission electron microscopy(TEM), X-Ray Diffraction(XRD) and scanning electron microscope(SEM), thermal treatment furnace, testing machine and so on to find out the plasticity mechanism at room temperature so that the best potential for deformation technology will get. The main work and conclusions are as follows:(1)The phase transformation temperature has been tested by the method of metallograph which is about 790±5℃.As the solution temperature increase and extend the solution time,αp phase decreased gradually. When the temperature is higher than Tβ,αpâ†'β completely, the quenched martensite is generated in the coarse equiaxed β grains. Stress-induced martensite generated during tension, which get the best mechanical properties and potential deformation when solution treated at 810℃for 1h.(2)The effects of aging process on the microstructure and ductility of TB6 alloy were studied.The results showed that,αs generated from β grain When aging after solution treated in β phase region. With the increasing aging temperature and aging time, α s grow up, which weakened the Orawan effect and get the material best mechanical properties when aging at 650℃ for 6h.(3) The influence of pre-deformation on microstructure and ductility results showed that: with the increase of pre-deformation, β grain boundaries become blurred,stress-induced martensitic transformation generated during tension. Material achieve the best mechanical properties with the combination effect of transformationinduced plasticity and twinning induced plasticity when under the 5%pre-deformation..For this reason, proper pre-deformation process can improve the plasticity without compromising the strength at the same time.(4)The effect of cooling rate on microstructures and ductility of TB6 alloy was analyzed, the results showed that: with the faster cooling rate,the βâ†'α won’t happen while quenched martensite generated in β grain. During tension, metastable β phase tranform α" gives the material higher ductility.When the cooling rate reduced, the βphase transform straight and thick α phase, which increase the slip distance between dislocation, causing low ductility. Therefore, the material get the best mechanical properties when water cooling.