Study On The Kinetics Of Sintered TiH₂ Titanium Alloy And Its Microstructure Evolution

Ti-6Al-4V alloy has become the highest utilization of titanium alloys because of itsexcellent performance,but it is limited by high manufacturing cost.At present,the main challenges for the development of titanium alloys are new technology,new technology and low cost.In this paper,a low cost TiH₂ powder is used to replace the titanium powder used in the production of titanium alloy.Ti-6Al-4V alloy and Ti-13Nb-13Zr alloy were prepared by vacuum sintering with the titanium hydride powder and other elements powder.The kinetic calculation of dehydrogenation in the process of vacuum sintering is carried out.The reaction activation energy of each stage is theoretically obtained,and a reaction model for the preparation of Ti-6Al-4V alloy by vacuum sintering in TiH₂-6Al-4V system is proposed.The obtained alloy samples were characterized by X ray diffractometer?XRD?,metallographic microscope and scanning electron microscope?SEM?.The TiH₂-6Al-4V system of dehydrogenation of Ti-6Al-4V alloy prepared by vacuum sintering dehydrogenation process,each stage of the reaction activation energy and phase transition process respectively is:350?to 365?,?-Ti?FCT?change to?-Ti?FCC?and the activation energy is 21.26kJ/mol;395?to 430?,?-Ti?FCC?change to?-Ti?FCT?and the activation energy is 157.57kJ/mol;490?to 555?,?-Ti?FCT?change to?-Ti?HCP?,the activation energy is 184.38kJ.The density of the compact is proportional to the pressing pressure,and the density of the alloy is inversely proportional to the pressing pressure.The Ti-6Al-4V alloys prepared by titanium powder and titanium hydride powder are?+?titanium alloy.But the alloy prepared by TiH₂ powder in addition to?and?phase,there is??-Ti.The alloy prepared by TiH₂powder is more compact than the alloy made from Ti powder.The microstructure of Ti-6Al-4V alloy prepared by titanium powder is short and clear,and there is a certain pore in the alloy.The alloy prepared by powder compact TiH₂,the microstructure is lamellar and short rod equiaxed?and?phase.There are equiaxed and lamellar phase in Ti-13Nb-13Zr alloy prepared by TiH2-13Nb-13Zr system using multi platform vacuum sintering process:the final thermal insulation temperature is 1450 C and the heat preservation time is 90minutes.The existence of the two kinds of tissues can explain the existence of stable?and?phase in the alloy.Moreover,the lamellar structure in the alloy did not show obvious trend of coarse grain or coarse grain,and the Nb of beta stable element played a role in the formation of titanium alloy,which made the beta phase of titanium stable after cooling down.Analysis based on XRD data reveals the presence of the?-Ti and?-Zr are hcp and the?-Ti?Nb and?-Zr are bcc.The activation energy and corresponding reactions at different stages of vacuum sintering are 400?to 500?,TiH₂ to TiH_X?51.05kJ/mol?,500?to 600?,TiH_X to Ti+ZrH₂ to ZrH_X?95.84kJ/mol?,600?to 800?,ZrH_X to Zr?/mol?.In this paper,cheap titanium hydride powder instead of titanium powder and other element powders were used to prepare Ti-6Al-4V alloy and Ti-13Nb-13Zr alloy by powder metallurgy method.The production cost of the titanium alloy was greatly reduced and the secondary process was shortened.This method improves the application potential of titanium alloy in civil field.At the same time,the activation energy of each system was calculated theoretically,and the dehydrogenation reaction and phase transformation process of Ti-6Al-4V alloy prepared by vacuum sintering in TiH₂-6Al-4V system were put forward.