Brazing of Titanium Honeycomb with Low-melting Zr-Ti-X-Y Brazing Alloy(s)

Hypo-eutectic solidification is utilized to form low-melting filler alloys in brazing titanium and/or titanium alloys.  Prior art (Zr₅₄Ti₂₃Ni₁₅Cu₈ ) eutectic filler alloy as well as new modified/improved filler alloys are used. 

The eutectic alloys in the Ti-Zr-Ni/Cu system consist of the three phases, on ductile Zr-rich solid-solution phase and two brittle intermetalic Zr₂Ni, and (Zr,Ti)₂Ni phases.  The Zr-rich hypo-eutectic alloys exhibit high strength, over 500MPa.  They have the same low solidus temperature (as the eutectic) but a higher  liquidus temperatures.

Using a hypo-eutectic Zr₆₀Ti₂₀Ni₁₃Cu₇ alloy T-joints of titanium were brazed at 950 °C. The fillets at the joints showed good wetting of the base materials and contained the Zr-rich and the other phases in fine and nearly homogeneous distribution.  During holding at temperature the faying surfaces of Ti base metals inter-diffuse with the  braze alloy, resulting in joint properties that were essentially equivalent to those of a diffusion-bonded layer. The joints thus ended up with excellent strength and toughness as might be expected from a diffusion-modified mostly-solid-solution-phase alloy.

The work demonstrated the use of low-melting filler alloys for brazing at relatively low temperatures. Well-wetted and quasi-homogenized fillet-alloys with good bond strength and toughness were formed.  The alloys are suited for joining titanium structures such as honeycomb, fins, and pyramid-type structures.