Research On Room-temperature Rolling Behavior Of Hydrogened TC4 Alloy

With the rapid development of the aerospace industry in recent years,the demand for titanium alloy sheet and strip increases sharply,especially in the TC4 alloy sheet and strip,which have better overall performance.However,due to TC4 alloy with characteristics of flow stress,high strength,low plasticity during cot deformation and so on,which lead to the rolling production of single pass less than 20%at room temperature for the normal TC4 sheet and strip.When simultaneous multi-cycle annealing treatment,it has seriously effect on the production efficiency and the quality of the TC4 sheet and strip.In this paper,TC4 alloy sheet and strip at the present stage of processing difficult and tedious production process,put forword to use titanium heat treatment technology to improve TC4 alloy rolling shaping at room temperature.In this paper,TC4 alloy Thermohydrogen processing(THP)(hydrogenation temperature,holding time and stable hydrogen pressure)made a systematic study,combined with the alloy under different hydrogen absorption capacity and alloy microstructure evolution,the influence of hydrogen treatment parameters on the hydrogen absorption of TC4 alloy was obtained.At the same time,the paper also studied OM、SEM、XRD and TEM analysis of TC4 alloy samples with different hydrogen content,combined with the changes of microhardness and rolling properties of TC4 alloy to study the evolution of microstructure,phase composition and content,hydrides generation law of TC4 alloy other evolution rules during hydrothermal treatment,to reveal hydrogen-induced plasticization mechanism at room temperature.In addition,TC4 alloy samples were also annealed and the hydrogen removal process of hydrogenation of TC4 alloy samples were studied,the effect of annealing temperature on the organizational performance,hydrogen removal process results and microstructure of TC4 alloy were studied.The experimental results show that when the hydrogenation temperature is 750℃,the hydrogen absorption efficiency of the alloy is the highest and the microstructure is not roughened obviously during the heat treatment of the TC4 alloy.Holding time of90min at 750℃hydrogenation temperature,the hydrogen of TC4 alloy organization distribute uniform,which has not significant concentration gradient macro,and no significant coarsening of the grain.With the increase of hydrogen content in alloy TC4-xH,the amount ofαin the alloy gradually decreases and the amount ofβphase increases.At the same time,~′、"andδphase were formed in the alloy,With the increase of hydrogen content,the content of"andδphase increased gradually and the content of~′decreased.Rolling of TC4-xH alloy with different hydrogen content showed that the ultimate rolling deformation of alloy increased first and then decreased with the increase of hydrogen content,reaching the maximum value when the hydrogen content was 0.9wt.%,compared with the rolling deformation rate of untreated alloy,the hydrogenation temperature increased by 21.12%at 750℃,and the hydrogenation temperature increased by 52.42%at 850℃.The study of TC4 alloy annealing found that with the annealing temperature increases,the alloy hardness declining,when the annealing temperature is 850℃,the organization coarsening,so the selection of the optimal annealing temperature is 800℃.For hydrogen removal of TC4-xH alloy,it was found that the removal of hydrogen at 850℃for 1h or 750℃for 4h can completely remove the hydrogen and the structure did not coarsen.Considering the processing efficiency,the best dehydrogenation process was selected at 850℃,and the holding time is 1h.