The microstructure and properties of TC4 brazed with a newly designed low-erosion Zr-based brazing filler
The welding of thin-walled titanium alloy is a key step in the manufacture of high-performance plate-fin titanium alloy heat exchanger.In order to solve the problem of serious base metal erosion during brazing of thin-walled titanium alloy,Zr-16Ti-9Cu-11Ni low melting point amorphous foil strip brazing material is designed and prepared in this study.The brazing filler is used to braze TC4 in the range of 840℃～980℃and holding time of 10～120min,and the typical microstructure and evo-lution process of the joint are analyzed by scanning electron microscopy(SEM),X-ray diffraction(XRD)and transmission electron microscopy(TEM).(Ti,Zr)2(Cu,Ni),α-Ti and β-Ti are com-posed.With an increase of brazing temperature and the extension of holding time,the brittle phase of the joint gradually decreases until it disappears,and the degree of base metal erosion gradually in-creases.The performance of the joint is evaluated by its shear strength.The results show that when the brazing temperature is 940℃and the holding time is 10 min,the strength of the joint is optimal,which is 386 MPa,but the degree of erosion of the base metal is large at this time,which is not suitable for welding in actual production.Considering the degree of erosion of the base metal and the shear strength of the joint,880～920℃is the appropriate production temperature range.The fracture path of the joint shows that the fracture mode of the joint is brittle fracture by observing the fracture morphology of the joint.
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