Technology And Mechanism Of Brazing Hydrogenated TC4 Titanium Alloy And C/SiC Composite

Titanium and hydrogen processing technology (THT) was used to change the alloy phase composition and microstructure in order to improve thermoplastic, thermal processing and diffusion of titanium alloy. THT was a hot new direction in the field of materials science. Present studies are most focused on the thermoplastic, hot workability and the residual of hydrogen titanium alloy, but there were few studies on their connectivity. C/SiC composite had excellent high temperature, wear and antioxidant properties. Therefore, to achieve an effective connection of the two new materials, could both be used in advanced rocket thrust chamber, but also provide a technical reference for connection of the hydrogenation titanium alloys and dissimilar materials. In this paper, AgCu foil and Ni foil were used for solder joint of hydrogen achieved Alloy TC4 and C/SiC composite. The purpose was to study the influence of brazing parameters on microstructure of joints;reveal the thermodynamics of interface product and its formation mechanism; study the influence of connection parameters on mechanical properties of joint; explain the fracture behavior of joints; optimize connection process.AgCu foil connection had a typical interface structure:titanium alloys/needle Veidemann organization/[Ti(s.s)+Ti2Cu] hypereutectoid organization/(Ti2Cu+TiCu+ Ti3Cu4) diffusion zone/Ag(s.s)+Cu(s.s)/Ti2Cu+Ti5Si3Cx/TiC/C/SiC Composite. At 840℃,10min insulation, Joint shear strength up to 97MPa. With the increased brazing temperature or holding time, the shear strength of joints first increased and then decreased, TiC reaction layer is the key to breaking the path.Pure Ni foil soldering, the typical interface structure:hydrogen TC4 titanium alloy/hypereutectic structure [Ti2Ni+Ti(s.s)]/Ti2Ni+a small amount of hypereutectic structure [Ti2Ni+Ti(s.s)]/TiC/C/SiC composites. Improveing brazing Specification, the joint interface product did not change significantly. The original dark gray block of Ti (ss) distribut in the Ti2Ni layer growed up; The thickness of Ti2Ni+Ti(s.s) eutectic on titanium side had been increased, a-Ti growing more coarse. At 1070℃,15min insulation, the joint shear strength is 110MPa and the highest.Hydrogen could improve brazing connectivity of titanium alloy for:Hydrogen could reduce theα→βtransition temperature which can change the alloy microstructure and increase dislocation density, improve the superplastic flow capacity of titanium alloy, achieve a good contact to solder foil. The decomposition of hydrogen activated the surface of the welded titanium, so solder and base materials could be soldered fast to atomic contacts; the addition of hydrogen in titanium. Caused vacancy concentration, increased the host elements Ti and alloying element diffusion and mutual diffusion coefficient, so that the diffusion rate increases and the diffusion distance increases, Diffusion and reaction between atoms became better.The hydrogen TC4 titanium alloy dehydrogenation decomposition between 600℃-950℃. At 750℃, the rate of dehydrogenation reaction rate is maximum. By analyzing the pattern of growth for the TiC reaction layer, this paper obtained growth kinetics parameters, then got the dynamic equations for growth behavior of the reaction layer.