Microstructures and mechanical properties of TiAl joint brazed with Ti-Mn-Fe-Ni-Zr system medium-entropy filler alloy

A five-element medium-entropy filler alloy with composition of Ti-(18 ~ 24)Mn-(12 ~ 18)Fe-(3 ~ 8)Ni-(3 ~ 8)Zr (wt.%) was proposed for vacuum brazing of TiAl-based alloy. The filler alloy was mainly composed of Ti-based solid solution and Ti-(Fe, Mn) compound dissolved with elements of Ni and Zr. The filler alloy ingot was ground into powder and then the filler powder was preset into the V-shaped groove butt joint with a gap of 50 μm. The Ti-Mn-Fe-Ni-Zr brazing alloy showed the liquidus temperature of 1060.1 °C, and also presented excellent wettability on TiAl substrate at 1110 °C for 10 min. The brazed joint mainly consisted of γ-TiAl, α₂-Ti₃Al, and residual brazing filler reaction phase. The brazing condition of 1210 °C/45 min exhibited the maximum joint thickness of 308 μm and the maximum area percentage of γ-TiAl phase of 33.77%, with almost elimination of residual brazing filler reaction phase within the joint, and meanwhile offered the maximum room-temperature tensile strength of 418 MPa, 70.85% of the base alloy. The joint fracture showed a mixed mode of intergranular and transgranular fracture.