Microstructure And Diffusion Mechanism Of Interface Between Ti And Ti_xNi_y

Recently,extensive research efforts have been dedicated to the bondingbetween Ti and Ni.However,the formation mechanism of the intermetallic compounds Tix Niy(the ratio of x to y is 1:1,2:1 and 1:3)and the influence of electric current on the interface of the system are still ambiguous.Moreover,the brittle intermetallic compounds formed at the interface impaired the performance of joint.So it's significant to study the phase evolution of Ti/Ni interface,and further the interface behavior of Ti/ Ti_xNi_y to improve the bonding strength of the joints.In this study,the bonding of Ti/Ti_xNi_y/Ni has been carried out through Field Activated Diffusion Bonding technology(FADB),in which the formation mechanism of Ti/ Ti_xNi_y and the effect of current on interface were discussed based on interface thermodynamics.Then,the bonding of Ti/ Ti_xNi_y amorphous compounds were carried out,the effect of both parameters of amorphous process and bonding temperature on microstructure and bonding strength of the joints were discussed subsequently.The results show that,in Ti/Tix Niy/Ni,the formation of TiNi3 has minimum standard reaction Gibbs free energy and that of Ti2 Ni has minimum increasing interface energy at 923 K among three intermetallic compounds.With the increasing of holding time,the thickness of the three diffusion layers increased,but only the growth of Ti2 Ni obeys the rule ?x2 = kt,the growth of TiNi3 suggests the possibility of two diffusion mechanisms.According to the diffusioninterface dynamics analysis results and thermodynamics calculation,the likely formation sequence of three intermetallic compounds is Ti2 Ni,TiNi3 and TiNi.The results also indicate that all phases grew to higher thickness when bonding was carried out in the presence of an imposed current.However,the direction of the current had no apparent effect on the formation or the thickness of any of the three phases.For the interface of Ti/Ti_xNi_yamorphous compounds,the results indicate that with the increasing of bonding temperature,the crystalline morphology of the bonding interface is more and more obvious,the bonding strength decreases.With the increasing of milling time,the amorphous morphology of the Ti/TiNi,Ti2 Ni amorphous compound bonding interface is more and more obvious and the bonding strength increases with the milling time.