Microstructure And Mechanical Property Of TiAl Alloy/316L Stainless Steel Vacuum Brazed Joint

Titanium alloy and stainless steel both are common structural material during engineering field,titanium alloy have advantages as high specific strength,low density and high temperature resistance;stainless steel has advantages as low cost,high corrosion resistance and good machinability.So their hybrid joints could develop advantages of performance and economy.However due to their difference of physical properties and chemical properties,we can't obtain sound joints by traditional welding method,so brazing method is applied in this research.To combine nice brazing properties of Ag-based filler metal and low cost of Ti-based filler metal.Zr-Cu-Ni-Al amorphous filler metal was obtained for the substrate of Zr-Cu eutectic structure refer to amorphous cluster theory.TiAl alloy and 316L stainless steel base metal were cut into large and small size,respectively.The specially designed fixture was used in shear strength test.Results of brazing test shows that sound brazed joints of TiAl alloy/316L stainless steel were obtained by Zr-Cu-Ni-Al amorphous filler metal,there are two diffusion zone and one brazing seam in the joint,the layer interfacial microstructure was TiAl base/a2-(Ti3Al)/AlCuTi/residual filler metal/Cu9Zr11+Fe23Zr6/Laves-Fe2Zr/?-(Fe,Cr)/316L base.The formation and thicken of ?2-(Ti3Al)phase and ?-(Fe,Cr)phase were controlled by diffusion of Al element from TiAl alloy to brazing seam and uphill diffusion of Cr element from 316L to brazing seam,their growth kinetic parameters were calculated and as follows:W?2-(Ti3Al)=3.639*10-6?p(-195.769/RT)(?m);W?-(Fe,Cr)=7.502*10-10?(-112.420/RT)(?m).Phases in brazing seam were mainly by the composition of Zr,Cu,A1 elements from residual filler metal.With the rising of brazing temperature and time,two diffusion zones became thicken;thickness of brazing seam mainly influenced by brazing temperature and homogeneity of brazing seam mainly influenced by brazing time,the reason is the chemical activity of elements was mainly affected by temperature and sufficient diffusion and reaction of elements was mainly related to brazing time.With the same variation trend of process parameters,shear strength of brazed joints increased first and then declined,as the peak value of 129 MPa at 1020?/10 min.After mechanical property test,the cracks started from Laves-Fe2Zr phase and extended into residual filler metal zone.The fracture form of brazed joints is brittle fracture,there are voids and facets on the fracture surface,Laves-Fe2Zr phse mainly existed in voids and residual filler metal phase and ?-(Fe,Cr)phase mainly existed on facets.