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Technology and Mechanism of Brazing Hydrogenated TC4 Titanium Alloy and C/SiC Composite

Author: WangYuXin
Tutor: FengJiCai
School: Harbin Institute of Technology
Course: Materials Processing Engineering
Keywords: Hydrogenation TC4 titanium alloy C / SiC composites Interface structure
CLC: TG454
Type: Master's thesis
Year: 2010
Downloads: 83
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Abstract


Hydrogenated titanium, i.e. by hydrogen thermal processing technology to change the phase composition and microstructure of the titanium alloy, obtained have improved thermoplastic, hot workability and diffusion of titanium, which is a popular direction of the emerging field of materials science . At present, domestic and foreign research mainly concentrated in the the home hydrogen titanium alloy thermoplastic hot workability as well as residual titanium processing, and the few studies of its connectivity. C / SiC composites have excellent high temperature, wear and antioxidant properties. Therefore, two new materials effectively connected, can be applied to both the advanced rocket thrust chamber, but also provide a technical reference for the home hydrogen titanium alloy with the connection of dissimilar materials. In this paper, AgCu foil and Ni foil the the home hydrogen TC4 titanium alloy and C / SiC composites brazed connection joints microstructure research brazing process parameters investigated; to reveal interface product formation thermodynamic factors and mechanism; analyze the connection process The parameters of the mechanical properties of joints law, Xie Ming joint fracture behavior mechanism to optimize the connection process. Connection AgCu foil, the typical structure of the interface: hydrogenation TC4 titanium alloy / acicular Veidemann organizations / [Ti (ss) Ti2Cu] hypereutectoid the organizational / (Ti2Cu TiCu Ti3Cu4) diffuse band / Ag (ss) Cu (ss) / TiCu Ti5Si3Cx/TiC/C/SiC composites. When T = 840 ℃ / t = 10min, the highest value of the joint shear strength 97MPa. With the brazing specifications to improve the shear strength of the joint first increases and then decreases TiC reaction layer fracture path key. Pure Ni foil brazing, the typical structure of the interface: hydrogenation TC4 titanium alloy / hypereutectoid organization Ti2Ni Ti (ss)] / Ti2Ni small amount of hypereutectic organizations [Ti2Ni Ti (ss)] / TiC / C / SiC composites. Brazing specifications increase, no significant change in the product of the joint interface. Original discontinuous distribution of gray-black block brazing the slit portion Ti2Ni layer Ti (ss) gradually grow; titanium side Ti2Ni Ti (ss) hypereutectoid tissue thickness increasing, α-Ti growth is more coarse. When T = 1070 ° C / t = 15 min, the shear strength of the joint highest, reached 110MPa. Hydrogen improve titanium brazing connectivity mainly: a hydrogen by reducing the α → β transition temperature, changing the density of titanium microstructure and increased bit error, improve superplastic rheology of a titanium alloy, and the brazing filler metal foils achieve good contact; decomposition of the hydrogen activation titanium surface to be welded, so that the base material of the solder and be welded faster achieve contact between atoms; the effect of hydrogen-induced weak bond can be reduced to the atoms binding energy, and enhance the vacancy density its migration ability, thereby making interdiffusion elements with enhanced self-diffusion, atomic diffusion reaction more fully. The article also integrated thermal analysis hydrogenation TC4 titanium alloy desorption characteristics found home hydrogen TC4 titanium alloy between 600 ℃ -950 ℃ dehydrogenation decomposition temperature dehydrogenation reaction rate reaches a maximum at 750 ℃. And TiC reaction layer thermodynamic and kinetic analysis to obtain the kinetic parameters of the growth of the reaction layer, through the analysis of its growth law, to reflect the behavior of the reaction layer growth kinetic equation.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process > Brazing
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