A Study On Theromhydrogen Processing And Room Temperature Deformation Behavior Of TB8Titanium Alloy

Theromhydrogen processing of titanium alloy is a promising processingtechnology. Hydrogen is usually used as a temporary component to adjust themechanical properties and the processing abilities of titanium alloys throughmodifying the microstructure. After hydrogenation treatment,the absorbinghydrogen property of TB8was investigated, which emphasize particularly onstuding the variation of hydrogen content when hydrogen flow rate, temperatureand time have changed. Hydrogenation on microstructure evolution and phasetransformation of TB8alloy was investigated by OM，SEM and XRD, the effect ofhydrogen on β transus temperature and the alloy element distribution was used byDTA and EDS.Compressive tests and microhardness tests were carried out at roomtemperature to study the influence of hydrogen content on the mechanicalproperties of TB8alloy at room temperature.The result indicated that hydrogen content in the alloy increases with gas flowrate increasing but eventually reached saturation;The relationship betweentemperature and hydrogen content is that increasing first then reducing and obeyedthe Sievert’s law after hydrogen content had reached peak; And the relationshipbetween hydrogen content and time in700℃meets:C_H(t)=0.619-0.619.After hydrogenation, the microstructure of TB8alloy occured significantchange. With increasing hydrogen content,the volume fraction of primary α phasedecreased gradually, β phase increased accordingly and then only β phase existedwhen hydrogen content up to0.68wt%. And hydrogenation also reduced the criticalcooling rate of ω phase; There are some phase transformations occured duringhydrogenation process: αâ†'αHâ†'αH+β_H，βâ†'β_H; In addition to hydride formed fromα phase through reaction during cooling process: αHâ†'α+TiHx,the eutectoidreaction happened when only fewer hydrogen existed: β_Hâ†'αH+δ,but after hydrogencontent reached a critical value, β phase can be preserved to room temperature andthe reaction also occured: β_Hâ†'ω. The result also found that hydrogen reduces βtransus temperature and redistributes alloy composition of TB8alloy.Hydrogen has a relatively small impact on plasticity of TB8alloy, however,due to the softening effect of the β phase,the yield strength σ0.2less than originalalloy.Strain hardening capacity gradually increased with the increasing hydrogencontent,mainly because of the hydrogen atom and hydride hindered dislocationmotion.The hardness of TB8alloy first increses then reduces with incresing ofhydrogen,and it is considered that hardening phase,hydride,softening phase andsolid solution strengthening are to interact.