The Synthesis Of Ti-based Amorphous Filler And Properties Study Of Vacuum Brazing TC4 Using Ti-based Amorphous Filler

Among Titanium alloy,Ti-6Al-4V?TC4?,accounting for about 60%of the titanium market due to structural demands for aerospace industries,medical applications etc.TC4 alloy contains 6 at.%Al as an?phase stabilizer and 4 at.%V as a?phase stabilizer,and its?-transus temperature?T_?,transformation from?to??is known as 1268 K.Therefore,reasonable joining techniques become more and more significant for the actual applications of Titanium alloys.Ti-based amorphous alloys,as a kind of metastable materials,have been widely used for brazing titanium alloys.In this article,firstly,the effects of different elements on the properties of amorphous ribbons were investigated by preparation of three series of amorphous ribbons(Ti_52+xCu_34-x4-x Zr₁₂Sn₂,Ti₅₂Cu_32-XZr_14+XSn₂,Ti₅₂Cu₂₆Zr_20-xNi_x Al₂,at%).The amorphous ribbon was characterized by XRD and DSC.The experimental results show that the addition of Zr,Cu,Ni decreased onset temperature of melting?T_m?,and the reduction of Cu decreased the amorphous forming ability obviously.Afterwards,four amorphous ribbons with lower onset temperature of melting?about 850??were selected.The TC4 alloy was brazed in vacuum furnace,using four Ti-based filler metals(Ti_51.44Zr_16.26Cu₃₀Sn_2.3,Ti_52.8Zr_18.6Cu_26.4Sn_2.2,Ti₅₁Cu₂₆Zr_14.4Ni_6.2Al_2.4,Ti₅₁Cu_27.8Zr_13.6Ni_4.6Al₃,at%).The filler metal was a amorphous alloy ribbon in size of 50?m thick and 10 mm wide,which were prepared by melt spinning.The influences of the brazing temperature and holding time on the microsturcture and mechanical properties of brazed joints were investigated in detail.The interfacial microstructure,composition analyses and mechanical property of the joints were inspected by an optical microscope,SEM,XRD,EDS,Vickers hardness tester and shear strength testing machine.When micro-cracks and voids formed in the joints,and the fracture occured in defects primarily.Forever,the shear strength increased and decreased with the brazing temperature and holding time increased.A lamellar?+?Widmanst?tten structure layer generated in the brazed joints in favor of the shear strength.Based on the XRD results from fracture surfaces,the appearance of brittle intermetallic compounds such as?Ti,Zr?₂?Cu,Ni?were confirmed and that is the reason why the shear strengths were deteriorated.For four filler metal,the maximum room shear strength were about 180MPa.The Ti_52.8Zr_18.6Cu_26.4Sn_2.2.2 filler metal with low Cu content had crystal cubic?-Ti due to low glass forming ability.The brazed joints were irregular and asymmetric,having unstable room shear strength.We have found that amorphous alloys,as a kind of metastable materials,can decrease the brazing temperature,homogenize the joints conponent,and hence obtain regular joint with high shear strength.