Preparation Of TiAl Alloys And Ti-6Al-4V Alloys By Molten Salts Electrolysis And The Research Of Their Properties

In recent decades,titanium and titanium alloys have become the representative of the new generation of high quality metals and have been widely used in aerospace structural parts and biomedical materials.However,high oxygen content and high preparation cost have restricted the development and application of titanium alloys,Therefore,it is very vital to improve the preparation methods and reduce the cost.This paper combines powder metallurgy with molten salts electrolysis,using near-net forming technology,to prepare titanium alloys at lower temperature by the action of high temperature and electric field,which has controllable process,low cost,low oxygen content and small segregation.The preparation of titanium alloys in the experiment includes TiAl alloys and Ti-6Al-4V alloys,that is,to remove oxides and reduce oxygen content from different metal surfaces by polarization in electrochemistry under 1000℃,and then to accelerate the diffusion and alloying of Ti and Al,V atoms.Based on this idea,the research and results of this study are as follows:(1)An attempt has been made to prepare the alloys by direct immersion sintering and applying potential electrolysis in different molten salts under Ar atmosphere.Through XRD,SEM,EDS and mechanical properties analysis,it is proved that the idea of preparing titanium alloys by molten salts electrolysis at high temperature is feasible,and the product performance after electrolysis is much better than that of soaking.(2)TiAl alloys were prepared using different kinds of molten salts,different potential,different temperatures and different electrolysis time.Through the analysis of XRD,SEM,hardness,compression test,the influence of these factors on the preparation of TiAl alloys was explored.The experimental results showed that the TiAl alloys were better by using CaCl2 molten salt,more potential(3 V),more time(12 h)and more temperature(950℃).(3)Ti-6Al-4V alloys were prepared by the same method.Through the analysis of XRD,SEM,hardness,compression test,it is found that Ti-6Al-4V alloys prepared by this method had better performance than TiAl alloys as a whole.The matrix is more complete,the deformation is smaller and the metallic luster is more bright.The hardness of TiAl alloys reached 240 HV and the compressive strength reached 108 MPa.The hardness of Ti-6Al-4V alloys reached 182 HV,and the compressive strength reached 173 MPa.(4)The porous titanium alloys were prepared by adding pore-forming agent and the pore structures of Ti-6Al-4V alloys were adjusted by adding 0-30 wt.%CaCl2 to the precursor and it can be removed successfully in the end.By analyzing SEM and compression test,it is found that the porosity is 29.4-60.1%,the pore size is 24.45-166.74 μm,and the elastic modulus is 1.77-6.09 GPa,which greatly adjust its range and meet the requirements of some medical implant materials.(5)The corrosion resistance of the porous Ti-6Al-4V alloys prepared was tested in Hank’s simulated body fluids.It is found that the alloys would produce a stable protective film in a very short period of time,and the corrosion potential moved forward as the pores of alloys increased,indicating that the protective film of alloys with higher pores was more stable and more difficult to corrode.