Study On The Interaction Between Defects And Hydrogen In Commercial Pure Titanium TA1 And Its Mechanical Properties

Titanium is widely used in chemical industry,shipbuilding and aerospace fields because of its high specific strength,corrosion resistance and other excellent properties.However,titanium is easy to absorb hydrogen in the environment,resulting in hydrogen embrittlement,which seriously affects its application and development.It is generally believed that the hydrogen embrittlement of titanium is mainly due to the formation of hydride after hydrogen diffusion and penetration in titanium matrix,which can also be attributed to the interaction between hydrogen and internal defects in titanium.Therefore,it is of great significance to study the existing forms of hydrogen in titanium and its interaction with defects for understanding the basic aspects of the effect of hydrogen on the properties of structural materials and predicting and solving the application problems related to hydrogen embrittlement.In this paper,pure titanium was hydrogenated by electrochemical hydrogen charging,low-energy ion implantation and plasma implantation.The mechanism and mechanical properties of the interaction between hydrogen and micro defects in pure titanium were studied by positron annihilation spectroscopy,transmission electron microscopy,scanning electron microscopy,thermal desorption spectroscopy and XRD.The main research contents and conclusions are as follows.A large number of single vacancies,vacancy clusters and hydrogen vacancy complexes were formed in the samples after ion irradiation under different conditions.A large number of hydrogen bubbles were observed in the irradiated samples by TEM.At room temperature,the formation of H_mV_n（m>n）in high dose irradiated samples inhibits the increase of S parameter.With the increase of irradiation temperature,the vacancy begins to recover,and some hydrogen atoms diffuse from the cascade region to the track region,forming a large number of hydrogen vacancy complexes in the track region.The increase of radiation dose and temperature is helpful to the formation of hydrogen vacancy complexes.When positron annihilates in the high momentum region,it is easy to obtain hydrogen related information.With the increase of hydrogen ion implantation energy,the damage range of irradiated samples expands,the formation rate of hydrogen vacancy complexes increases,and the radiation hardening phenomenon is more obvious.After electrochemical hydrogen charging under different conditions,a large number of vacancy type defects are formed in the samples.At the same time,three types of hydrides are observed in the samples,namely,ε-Ti H₂、δ-Ti H_x（1.5≤X<2）andγ-Ti H.With the increase of parameters,the content of hydrides increases.Excess hydrogen atoms combine with vacancy to form hydrogen vacancy complex（H_mV_n）,which reduces the effective volume of vacancy clusters.The coincidence Doppler broadening spectroscopy（CDB）was used to characterize the titanium hydride and hydrogen vacancy complexes in the hydrogen charged samples.The different annihilation mechanisms of positrons in the hydride and hydrogen vacancy complexes were analyzed.By establishing the annihilation diagram of positrons in Ti,it was shown that the hydrogen atom affected the positron annihilation environment by changing the electronic structure around the titanium atom and defects.The interaction between irradiated defects and gas atoms was studied by means of positron annihilation spectroscopy.It is found that the damage rate of deuterium ions is small in the fully annealed pure titanium samples,and deuterium atoms are mainly occupied in the gap and easily detected by positrons.The defects in irradiated samples are easy to combine with deuterium atoms to form D_mV_n complex,which reduces the effective volume of vacancy clusters in irradiated samples.The annihilation rate of the incident positron in these defects containing D_mV_n is reduced,which slows down the hydrogen ion irradiation damage.