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摘要
TiH2-65Ni(mass fraction, %) +TiB2 composite powder fillers were used to braze Ti-47Al-2Nb-2Cr-0.15B alloy at 1230 ℃ for 10 min. The interfacial microstructure and formation mechanism of the TiAl brazed joint and its evolution process as a function of the in-situ synthesized TiB content (volume fraction of 0 ? 40%) during brazing were investigated. Besides, the relationship between interfacial microstructure and shear strength of the TiAl brazed joint as well as the strengthening mechanism of in-situ synthesized TiB whiskers were analyzed. The results show that TiAl brazed joints are divided into three interfacial reaction layers and mainly consisted of Al3NiTi2, Ti3Al and TiB. The ability to refine microstructures as well as strengthening and toughening effects of TiB whiskers increase with increasing the in-situ synthesized TiB content (volume fraction of 0 ? 20%), which is beneficial to improve the shear strength of the TiAl brazed joints. The maximum shear strength of 332.54 MPa is obtained when the in-situ synthesized TiB content is 20%. When the TiB whiskers content increases up to 30% and 40%, the TiAl brazed joints become embrittle and form microvoids, resulting in reduction of the shear strength to 206.75 MPa and 170.43 MPa, respectively. The brittle fracture occurs in the isothermal solidification layer Ⅱ occupied with continuous block brittle hard Al3NiTi2 after shear tests for the TiAl brazed joints. ? 2023 Central South University of Technology.
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