| Ti3Al-based alloy has the advantages of high melting temperature, high elastic modulus and good oxidization-resistance at high temperature. It has been used widely in aeronautic and space industry, which shows its unique superiorities. However, when Ti3Al-based alloy is used in practice, the bond technology is one of important part in processing, so it is necessary to investigate the bond of Ti3Al-based alloy. This paper studied the vacuum brazing and high frequency induction brazing of Ti3Al-based alloy to meet the requirements in aeronautic and space industry. The effect of different brazing methods, filler metals, brazing parameters on the interfacial microstructure and joint strength has been analyzed. According to the analytic results, the optimum brazing parameters for different filler metals have been given to acquire an excellent joint.Using vacuum brazing and TiZrNiCu filler metal, intermetallics Ti2Ni, Ti(Cu,Al)2 and Ti[s,s] were formed in the interface of joint. The formation of excessive intermetallics Ti2Ni and Ti(Cu,Al)2 decreased the shear strength. When the heating temperature was increased, Ti2Ni and Ti(Cu,Al)2 increased and Ti[s,s] decreased. If the holding time was lengthened, no new reaction phase was produced, and the reaction of Ti, Al, Ni, Cu element in the interface was more sufficient, Ti2Ni and Ti(Cu,Al)2 increased and Ti[s,s] decreased. The optimum parameters were heating temperature T=1323K,holding time t=5min. The maximum shear strength was 253.6MPa。Using vacuum brazing and AgCuZn filler metal, intermetallics TiCu, Ti(Cu,Al)2 were formed at the interface of joint, the shear strength of the joint was decreased because of the formation of excessive TiCu and Ti(Cu,Al)2. When the heating temperature was increased, TiCu and Ti(Cu,Al)2 increased. If the holding time was lengthened, the reactions of Ti,Al,Cu element in the interface were more sufficient, TiCu and Ti(Cu,Al)2 increased. The optimum parameters were heating temperature T=1173K,holding time t=5min. The maximum shear strength was 125.4MPa.Using high frequency induction brazing and AgCuZn filler metal, brittle intermetallics, holes and oxidation existed in the joint on the condition of certain brazing parameters. The optimum parameters were heating temperature T=1133K, holding time t=5s, the maximum shear strength of the joint was 124.4 Mpa. The maximum shear strength was as high as the strength of vacuum brazing, so it is ideal for the bonding of Ti3Al to use high frequency induction brazing and AgCuZn filler metal, and high frequency induction brazing can replace vacuum brazing.Using high frequency induction brazing and TiZrNiCu filler metal, the shear strengths of the joints were low. The maximum shear strengh was only 102.1MPa, which was lower than the maximum strength of vacuum brazing. The reasons may be that excessive intermetallics, holes and oxidation existed in the joint. So TiZrNiCu filler metal isn't fit for non-vacuum brazing.The stress variation, stress distribution and crack-sensitive regions during the cooling process of brazing have been studied by Marc non-linear software. The result indicated that the stress was concentrated on the end of the joint interface and inner filler metal. If brittle intermetallics were produced in these areas, the fracture of joint would occur frequently. This paper has also studied the effects of thickness of filler metal and brazing compressive load on the stress of the joint. It has been proved that if the thickness of interlayer was thinner, the residual stress was lower, but excessive thickness of the interlayer was not fit for the joint, and the thickness was dependent on the performances of filler metal and based alloy. If compressive load was increased, the residual stress of all areas was decreased when the compressive load was loaded vertically on the surface during brazing process, but the residual stress distribution wasn't changed. So loading suitable compressive load is useful to decrease the residual stress.
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