Effect of in-situ synthesized TiB whiskers on interfacial microstructure and shear strength of γ-TiAl joint vacuum brazed with TiH2-Ni-TiB2 fillers

TiH2-61Ni + TiB2 (at%) composite powder fillers were innovatively designed and prepared by mechanical ball-milling to vacuum braze Ti-47Al-2 Nb-2Cr-0.15B (at%) alloy at 1230 ℃ for 10 min with theoretical in-situ synthesized TiB whiskers varied from 0 to 30 vol%. The interfacial microstructure of the TiAl brazed joint and the relationships among in-situ synthesized TiB whiskers volume percentage, interfacial microstructure and joint property were studied in detail. Results show that the interfacial microstructures of the TiAl brazed joints are γ-TiAl/Ti3Al + AlNiTi (layer І)/AlNiTi + Ti3Al (layer Ⅱ)/Ti3Al + AlNiTi + TiB (layer Ⅲ)/AlNiTi + Ti3Al (layer Ⅱ)/Ti3Al + AlNiTi (layer І)/γ-TiAl. The variation of the in-situ synthesized TiB whiskers volume percentage significantly influences the formation and evolution of the interfacial microstructure, as well as the shear strength of the TiAl brazed joints. The maximum shear strength of 341 MPa is obtained when TiB is 15 vol% and almost 85% higher than the brazed joint without TiB. The initiation and propagation of the shear fracture change from layer II to layer III once the TiB exceeds 15 vol%, and all fracture surfaces are characterized as brittle cleavage fracture.