Hot Bending/Diffusion Bonding Combination Process For Three-sheet Structure Of Ti₂AlNb Alloy

With the development of aerospace industry and other advanced technologies, Ti-Alintermetallic compound which has high temperature strength and low density hasalready attracted increasing attention. Therefore, more and more specialists of the hightemperature materials field pay attention to Ti2AlNb alloy which is regarded as one kindof Ti-Al intermetallic compounds. However, it is difficult to manufacture complexstructures with Ti2AlNb alloy because of its poor plastic property in room temperature.This is detrimental to its popularization and application.Faced with this situation, the hot deformation behavior and diffusion bonding ofTi2AlNb alloy were studied in this paper. And the hot bending/diffusion bondingcombination process was developed to form three-sheet structure of Ti2AlNb alloy. It ishelpful to improve the practicality of Ti2AlNb alloy.Through high temperature tensile experiments, the true stress-strain curve of Ti2AlNballoy with different strain rate and temperature has been obtained. This is helpful tounderstand the hot deformation character of Ti2AlNb alloy. And material parameterswere obtained by linear regression of the relationship between peak stress σpand strainrate. The Arrhenius constitutive equation of Ti2AlNb alloy was obtained from theseparameters. It could provide the basis for numerical simulation and develop reasonablebending forming process parameters.Hot bending process simulation of corrugated plate were carried out by Dynaformsoftware. Comparing different size precision by different forming temperature, frictioncoefficient and punch fillet, it is easy to find that the higher forming temperature, thegreater the punch fillet, and the smaller the coefficient of friction, the minimumthickness of bending forming parts are closer to the original thickness of Ti2AlNballoy. According to results of the simulation, the optimal parameters of hot bendingforming were: forming temperature:1040℃, punch fillet: R1.5mm, friction coefficient:0.2.The solid diffusion bonding test of Ti2AlNb alloy were carried out in the vacuumfurnace. Through microstructure analysis and mechanical testing, it could find that thehigher temperature and longer holding time are, the welding rate of interfacial jointsimprove. The quality of diffusion bonding is best under the parameter of P=10MPa,T=1150℃, t=90min, and he high temperature shear strength could reach497MPa in thiscondition. The observation of shear fracture showed most modes of fracture werecleavage fracture and few were dimple fracture.The hot bending/bonding combination process of three-sheet structure was formulated.Then the bending mold and diffusion bonding mold were designed. After this, the hot bending test and diffusion bonding test with reasonable process parameters were carriedout in the vacuum furnace to obtain the three-sheet structure of Ti2AlNb alloy. Itchecked the quality of three-sheet structure after forming test, including the analysis ofprecision, the observation of the microstructure and the compressing test. The goodquality of three-sheet structure proved the rationality of the hot bending/diffusionbonding combination process.