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Process and Mechanism Research on Self-Propagating Reaction Assisted Brazing between TiAl Alloy and C/C Composites

Author: ZuoXiaoChao
Tutor: FengJiCai
School: Harbin Institute of Technology
Course: Materials Processing Engineering
Keywords: C / C composites TiAl alloy SHS reaction Connection Interface structure
CLC: TG454
Type: Master's thesis
Year: 2011
Downloads: 85
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Abstract


Metal and nonmetal materials, connections are connected to a hot research field, this paper for the C / C composite material (referred to as CC) and two kinds of hot TiAl alloy lightweight structural materials connectivity needs, systematic study of both self-propagating reaction auxiliary brazing. Take the test and the method of combining theoretical analysis carried out to connect the middle layer optimization. SEM and EDS analysis, X-ray diffraction analysis, strength testing, and differential thermal analysis method to study the different parameters of the interface connector microstructure and mechanical properties. With this special connection method and the evolution of the interface structure and organization of a systematic analysis reveals the connection process parameters on the joint performance and interface structure were investigated. Thermodynamic analysis system based on the results calculated preferably Ti-Al and Ti-Al-C adiabatic temperature intermediate layer system, and identified to ensure the lowest self-propagating reaction preheating temperature, while the Ti-Al-C system SHS The apparent activation energy was calculated. By DSC by means of an intermediate layer of a preliminary analysis of the reaction mechanism, the use of an intermediate layer of different composition solder powder and preferably in the appropriate parameters to achieve a Ti-Al alloy and Preparation of C / C composites from spreading once connection of a typical interface structure of the joint to determine the interface reaction phase. TiAl-based results and CC first connection, preferably a AgCuTi solder and solder BNi2 TiAl and CC were secondary connections. AgCuTi solder used and the intermediate layer Ti-Al, a typical structure of the joint interface CC / TiC / Ag (ss) Cu (ss) / AlCu 2 Ti Ti (Cu, Al) 2 / TiAl 3 Ti 3 Al TiAl Ti / TiAl 3 TiAl 2 / TiAl; using BNi2 solder and Ti-Al-C intermediate layer, the typical structure of the joint interface CC / Cr7C 3 / residual BNi 2 / NiAl Ni 2 Al 3 / TiAl 3 TiAl Ti 3 Al Ti TiC / TiAl 3 TiAl 2 / TiAl. Heating temperature on TiAl / CC joints greater impact microstructure and mechanical properties, with the heating temperature, the middle layer heat release increases, solder and CC side of the interface reaction layer becomes apparent gradually increased joint strength. At 750 ℃ ??/ 2 0min / 2 0MPa conditions, using AgCuTi solder and Ti-Al-C intermediate layer to obtain maximum joint strength is 11MPa, close to conventional brazing strength , joint fracture in the TiC layer; at 800 ℃ / 2 0min / 2 0MPa used under the conditions BNi 2 solder and Ti-Al-C the intermediate layer to obtain the highest joint strength of 10.6MPa, joint fracture in the Ni-Al layer. Holding time on the microstructure and mechanical properties of joints is not obvious. CC on TiAl with auxiliary self-propagating reaction brazing connection mechanism was analyzed and found that self-propagating reaction takes place in Al melted, the heat released by the middle layer quickly passed to the solder melts the solder side and to promote and CC, solder and intermediate Reaction between the layers. In TiAl base metal side generated TiAl 3 layer, resulting TiAl 3 continue to TiAl base metal reacts TiAl 2 layer.

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