摘要
This work has successfully proposed a solution to produce robust Nb-interlayer-inserted Ti-6Al-4V/Si_(3)N_(4)joints optimized for a maximum operating temperature of 873 K;transient liquid phase bonding(TLPB)of Ti-6Al-4V/Nb side was carried out with Cu and Ni fillers to suppress brittle intermetallic compounds(IMCs),whereas brazing of Nb/Si_(3)N_(4)side was performed using a highly ductile Ti-added Ag-rich filler for effective residual-stress relaxation.A sound yet simple one-step bonding process incorporating simul-taneous TLPB and brazing was achieved with a relatively short holding time of 10 min at 1213 K.TLPB of Ti-6Al-4V/Nb side with Cu and Ni foils of 2-μm-thick each as a laminated filler suppressed brittle Ti-based IMCs and developed a homogenized microstructure consisting mainly of(α+β)-Ti via isothermal solidification.Meanwhile,brazing of Nb/Si_(3)N_(4)side with 100-μm-thick SILVER-ABA filler(92.75Ag-5Cu-1Al-1.25Ti mass%)foil enhanced interfacial bonding with sufficient total Ti content and accommodated residual stress better than conventional eutectic Ag-Cu-based fillers,and it was verified by finite element analysis with consideration of materials’temperature-dependent elasto-plastic properties.All joints with a bonding area of 10 mm×10 mm were tested via symmetrical four-point bending from room temper-ature(RT)to 873 K fractured from Nb/Si_(3)N_(4)side.When re-heating the joints from RT to 673 K,frac-ture initiation gradually shifted from Si_(3)N_(4)towards interfacial-compounds/Si_(3)N_(4)interface and bending strengths maintained∼220 MPa as weakening of SILVER-ABA filler was compensated by residual-stress relaxation in Si_(3)N_(4).When tested at 873 K,joints fractured mainly across the Ag-rich solid solution in a ductile manner and bending strength degraded by∼20%to 171 MPa as weakening of SILVER-ABA filler dominated.
基金
This work was financially supported by the Light Metal Educa-tional Foundation,Inc.of Japan.
