A novel approach for brazing MgF₂ ceramic to TA15 alloy using AgCu/GH4169/Bi₂O₃–B₂O₃–ZnO composite braze fillers

A two-step brazing process was successfully employed to join MgF₂ ceramic and TA15 alloy using eutectic Ag–28% (in mass fraction) Cu alloy and Bi₂O₃–B₂O₃–ZnO (BBZ) glass as fillers, by introducing a 100 μm thick GH4169 interlayer. Multiscale characterization revealed that interdiffusion and reaction occurred at the joint interfaces. As a result, a reliable joint system consisting of TA15/TiCu/TiCu₂Al/Ag(s,s) + Cu(s,s)/TiCu₂Al/Ti–Cu– Ni + Ag-rich layer/GH4169/nano-oxide layer/glass/Mg₃(BO₃)F₃+MgO + MgF₂ reaction layer/MgF₂ was formed. The GH4169-interlayer exhibited adaptive compatibility though its interaction with Ag–Cu and BBZ glass fillers, effectively accommodating strong interface bonding and thermal mismatch stress between TA15 and MgF₂ substrates. It shows an excellent shear strength (32 MPa, at room temperature) as well as thermal cycling stability without any cracking or spallation observed after the 20 thermal shock cycles between room temperature and 300 °C. It provides valuable insights into designing highly reliable ceramic/metal joints that demonstrate superior stability and adaptability in specific applications.