| The internal pressure diffusion was employed to clad titanium to steel in this thesis. The interface diffusion behaviors of titanium inner-clad carbon steel bimetallic tube and the effect of decarbonization on surface combination have been investigated by means of optical microscope, scanning electron microscope(SEM) and alternating bending test. The influences of process parameters, such as surface preparation method, pressure, diffusion temperature and time, on interface bonding strength of titanium-steel bimetal have been analyzed.The interdiffusion phenomenon near the interface of titanium-steel was observed after drawing and anneal. A dense compound layer is formed to prevent the diffusion. The thickness of compound layer is dependent on the annealing technics: the higher temperature and the longer time, the thicker. Where there exists a decarbonization layer on surface, the atom diffusion mechanism is influenced: during the initial stage, there is titanium and ferrum diffusing; with the extending of annealing time, carbide appears, which prevent the diffusion of titanium and ferrum. As the annealing temperature increases, TiFe, TiFe2 and other compounds come forth on the interface. The appearing temperature at which TiFe and TiFe2 form is lower in the surface with a decarbonization layer.There exists a maximum surface combination strenth with the increase of temperature, which a ppears when temp erature is between 750℃ and 800℃. The surface combination strength decreases sharply as the annealing period is prolonged. The plastic annealing of surface is better after preserved between 750℃ and 800℃ for 30 minutes, which could endure some kind of distortion. The diffusing rate of carbon atoms is so faster that they, could get through the decarbonization layer at a high speed. Therefore, the carbide is formed on surface, which decreases the effect of surface combination, and less influence of decarbonization layer on intensity of surface combination is seen. |
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