Process And Mechanism Research On Self-propagating Joining Between C_f/al Composites And Tial Alloy

In the paper, carbon fibre reinforced aluminum composite materials (noted as C_f/Al)and TiAl was joined by self-propagation high-tempertature synthesis welding. Theforming mechanism of interface was studied systematically. Basal experiments andtheoretical analyses were carried out to obtain the proper interlayer. The exothermicmechanism of interlayer, the microstructure and mechanical property of the joint and theinfluence of parameters on joining quality and interfacial reaction were investigated bymeans of differential thermal analysis (DTA), scanning electron microscope (SEM),energy disperse spectroscopy (EDS), strength test and X-ray diffraction (XRD). At last,the forming mechanism of the microstructure of joints was explained.Taken into the character of C_f/Al, its weldability was analysed. Based on thethermodynamic theory and choosing principle of interlayer, the interlayer was selected.Using DTA analysis and basal experiments, the interlayers was confirmed finally. Basedon the results of thermodynamics calculation, the adiabatic temperatures of Ti-Al-C-Cuand Al-Ni-CuO powder interlayers were calculated. The minimum preheatingtemperaturet to hold the self-propagation reaction was ensured, and the apparentactivative energy was aslo calculated.C_f/Al and TiAl was joined by self-propagation high-tempertature synthesis weldingby means of TE (thermal explosion) mode and SHS (self-propagation high-tempertaturesynthesis) mode with Ti-Al-C-Cu interlayer. The perfect joint was obtained. On the sideof C_f/Al, there was Al2Cu compound producing both in C_f/Al and the interface betweenthe interlayer and C_f/Al because of the diffusion of Cu. On the side of TiAl, TiAl3compound emerged along the interface between interlayer and TiAl. In the interlayer,there were lots of TiAl3, a little Ti(Al Cu)2and bits of compound of Al-Cu. The heatingtemperature had great inpact on the microstructure and shear strengths of joints. With thetempertature increasing, the mechanical properties of the joints rised firstly and thendropped deeply. The holding time had little influence on the microstructure andmechanical property of the joint. The shear strengths of joints went up firstly and thenbecame steady with the holiding time adding. The shear strength of joints reached25.89MPa. The forming mechanism of interfaces between C_f/Al and TiAl was explained,giving that the formation of Al liquid was the key for SHS joining.C_f/Al and TiAl was joined by self-propagation high-tempertature synthesis weldingwith Al-Ni-CuO interlayer in the vaccum furnace. On the side of C_f/Al, there was NiAl3compound emerging in the interface between the interlayer and C_f/Al. On the side ofTiAl, TiAl3compound emerged along the interface between interlayer and TiAl similar tothat of Ti-Al-C-Cu interlayer. In the interlayer, there were lots of NiAl3, a little Al2O3and bits of compound of Al-Cu. The heating temperature had enormous affect on themicrostructure and shear strengths of joints. With the tempertature increasing, themechanical property of the joint increased firstly. When the temperature exceeded650℃,it descended rapidly. When the holding time surpassed10min, it had hardly influence onthe microstructure and shear strengths of joints. The shear strength of joints reached39.99MPa. The forming mechanism of interfaces between C_f/Al and TiAl wasinvestigated, reaching that the reaction between Al and CuO at low temperature was keyfor SHS joining.