Influence Of Welding Parameters On The Properties Of Ti₂AlNb/TC18 Welding Interface

TC18 titanium alloy is widely used in aircraft body and large bearing parts of landing gear,due to its high strength and toughness,good plasticity.Ti₂AlNb alloy has excellent properties at high temperature,high specific strength and specific modulus.It is often used as a lightweight high temperature structural material in aero engines.The Ti₂AlNb/TC18 assemblies obtained by joining technology can give full play to their respective advantages of the two alloys.The vacuum electron beam welding of Ti₂AlNb alloy and two TC18 alloys with different histomorphology was carried out by using different welding speed and welding current.Tensile tests at room temperature and high temperature were carried out for the obtained welding parts.The macro morphology and microstructure of Ti₂AlNb/TC18welding interface were observed,and the phase composition of the weld,microhardness and the diffusion law of the alloy elements in the welding interface are analyzed.The main results are as follows:The welding speed of 6mm/s under the welding current of 25mA and 28mA is beneficial to improve the room temperature tensile strength of the Ti₂AlNb/TC18-basket specimen,and the welding speed of 8mm/s under the welding current of 31 mA is beneficial to improve the room temperature tensile strength of the Ti₂AlNb/TC18-basket specimen.The welding speed of 6mm/s is beneficial to improving the room temperature tensile strength of Ti₂AlNb/TC18-duplex specimen.At the welding speed of 6mm/s,the welding current has great influence on the room temperature tensile strength of Ti₂AlNb/TC18-basket and Ti₂AlNb/TC18-duplex.At the welding speed of 8mm/s,the welding current has little effect on the room temperature tensile strength of Ti₂AlNb/TC18-basket and Ti₂AlNb/TC18-duplex.The influence of welding speed on tensile strength,yield strength,elongation and reduction of area of Ti₂AlNb/TC18-basket and Ti₂AlNb/TC18-duplex specimen at high temperature is small.The tensile strength and yield strength of Ti₂AlNb/TC18-basket specimen obtained by using 25mA welding current under the welding speed of 6mm/s are good,while the elongation and reduction of area obtained by using 31mA welding current are good.The tensile strength,yield strength,elongation and reduction of area of the Ti₂AlNb/TC18-duplex specimen obtained by using 31mA welding current under the welding speed of 6mm/s are all good.The optimum tensile properties of Ti₂AlNb/TC18-basket specimen are room temperature tensile strength 833MPa,high temperature tensile strength 813MPa,high temperature yield strength 682MPa,high temperature elongation 16.5%,and high temperature reduction of area 69%,and the corresponding welding parameters are welding voltage 150k V,welding current 25mA,aggregation current 1950mA,welding speed 6mm/s.The optimum tensile properties of Ti₂AlNb/TC18-duplex specimen are room temperature tensile strength 922MPa,high temperature tensile strength 772MPa,high temperature yield strength 672MPa,high temperature elongation 17.3%,and high temperature reduction of area 73.5%,and the corresponding welding parameters are welding voltage 150k V,welding current 28mA,aggregation current 1950mA,welding speed 6mm/s.The weld joint of Ti₂AlNb/TC18-basket and Ti₂AlNb/TC18-duplex specimen is composed of?₂,B2,AlTi,Al₂Ti,Al₃Ti,AlTi₃ and NbTi₄.The microhardness of the weld zone is the highest in both Ti₂AlNb/TC18-basket and Ti₂AlNb/TC18-duplex specimen,and the elements in weld zone of the Ti₂AlNb/TC18-basket and Ti₂AlNb/TC18-duplex specimen are all fully diffused under the welding current of 25mA and the welding speed of 6mm/s.