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悉尼材料加工工程论文-C/C复合材料与TC4钎焊接头组织及性能Study on Microstructure and Mechanical Properties of C/C Composite and TC4 Brazed Joint.In the recent development of new materials, C/C composite has been considered to be an ideal high temperature material with potential application in aerospace field because of its low density, high thermal conductivity, high thermal shock and fatigue resistance, especially its high mechanical properties at high temperature. It has been successfully used as aircraft brakes materials, armour materials for the divertor and nozzle materials.

The nozzle component made of C/C composite and TC4 can greatly decrease the weight and increase the efficient of rocket engine. In this paper, the interface reaction mechanism was analyzed, and the relationship between microstructures and mechanical properties was investigated when the C/C composite and TC4 were brazed with AgCuTi and TiZrNiCu （adding to interlayer） filler metals.The interface structure was C/C composite/TiC/TiCu/Ag（s.s）+Ti3Cu4+TiCu/ Ti3Cu4/TiCu/Ti2Cu/Ti（s.s）+Ti2Cu/TC4 with AgCuTi filler metal.

The kinds of the reaction products were not changed but the thicknesses of the reaction layers were changed with different brazing parameters. With increased brazing temperature and bonding time, the thicknesses of the TiC/TiCu and Ti3Cu4/ TiCu/Ti2Cu/Ti（s.s）+Ti2Cu increased, while the Ag（s.s）+Ti3Cu4+TiCu in the middle of brazing seam decreased as well as the amount of TiCu+Ti3Cu4 decreased. When the brazing temperature was 1183K for 600s, the optimum shear strength was 25MPa. The shear strength decreased at other brazing parameters.

The fracture surface analysis showed that the fracture location was related to the orientation of carbon fiber. When carbon fiber was parallel to the joined surface, the joints were fractured in the composites. When carbon fiber was vertical to the joined surface, the joints were fractured at TiC layer at low and middle brazing parameters and the joints were fractured at TiC layer or TiCu/Ti2Cu interface at high brazing parameters. https://www.51lunwen.org/australiathesis/ 

To release residual stress and increase the mechanical properties at high temperature, C/C composite and TC4 were brazed with TiZrNiCu filler metal and Cu/Mo composite interlayer.

The interface structure was Cu/Cu+（51）Zr14/Ti2（Cu,Ni） +Ti（Cu,Ni）+TiCu+Cu2TiZr/TiC/C/C composite at low brazing parameters. With the increased brazing parameter, TiCu and Cu2TiZr disappeared, and Ti（Cu,Ni）2 appeared. The interface structure was Cu/Cu51Zr14/Ti2（Cu,Ni）+Ti（Cu,Ni）+ Ti（Cu,Ni）2/TiC/C/C composite. At high brazing parameter, the interface structure was Cu/Cu51Zr14/Cu（s.s）+Ti（Cu,Ni）2/TiC/C/C composite. The thicknesses of Cu51Zr14 and TiC reaction layers increased with the increased brazing temperature and holding time. The maximum shear strength was 21MPa at room temperature and 27MPa at 923K when the brazing parameter was 1173K for 300s, which can meet the performance requirement. The shear strength gradually increased with the increased thickness of Cu, but the maximum shear strength was no more than 23MPa. The fracture surface analysis showed that the situation of fracture was related to the orientation of carbon fiber.

When carbon fiber was parallel to the joined surface, the joints were fractured in the composites. When carbon fiber was vertical to the joined surface, the joints were fractured at TiC at low and middle brazing parameters and the joints were fractured 本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。