Microstructural evolution mechanisms of Ti600 and Ni-25%Si joint brazed with Ti-Zr-Ni-Cu amorphous filler foil

A commercial Ti-Zr-Ni-Cu amorphous filler foil was applied to braze the high-temperature Ti600 and Ni-25at%Si, resulting in the good joint between both of alloys. The interfacial microstructure of Ti600/Ti-Zr-Ni-Cu/Ni-25at%Si brazed joint at 1213 K for 10 min is mainly comprised of the continuous Ti2Ni phase. Most of Ti-rich phases such as α-Ti, β-Ti, Ti3Al, Ti2Ni, (Ti,Zr)2(Ni,Cu) and (Ti,Zr)2Si formed in the vicinity of the Ti600 substrate except that Ti5Si3 precipitates near the Ni-25at%Si region, resulting in the formation of six distinct layers. The corresponding formation mechanism were clarified. The Ti5Si3 and Ni31Si12 were firstly formed during the initial stage followed by diffusion reactions at Ni-25at%Si side. The continuous Ti2Ni phase formed through the reaction of Ti(L) + Ni(L) → Ti2Ni. α-Ti, Ti3Al, (Ti,Zr)2(Ni,Cu) and (Ti,Zr)2Si in the brazing joint precipitated through a solid-solid phase transformation.