Microstructure evolution and mechanical properties of Ti 22Al 25Nb alloy joints brazed with Ti Ni Nb alloy

• DOI: 10.1016/j.matchemphys.2016.07.062
• Publication Date: 2016-07-27T22:34:30Z
• Authors: Y. Wang; X.Q. Cai; Z.W. Yang; Q.W. Qiu; D.P. Wang; Y.C. Liu
• Keywords: 02 engineering and technology; 0210 nano-technology

Abstract Ti 45 Ni 45 Nb 10 (at.%) brazing alloy, fabricated by arc melting, was successfully used to braze Ti 22Al 25Nb (at.%) alloy. The microstructures of Ti 45 Ni 45 Nb 10 brazing alloy and Ti 22Al 25Nb alloy brazed joints were analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and micro-area X-ray diffraction (XRD). The effects of the brazing parameters on the interfacial microstructure and mechanical properties of the Ti 22Al 25Nb alloy brazed joints were investigated. The results showed that the joint was primarily comprised of two characteristic zones: diffusion zone I and central zone II, and the reaction phases formed in the brazed joint were the B2, O, τ 3 , and Ti 2 Ni phase. The crystal orientation of B2 phase in diffusion zone I was consistent with that in the Ti 22Al 25Nb substrate. The O phase was precipitated from the B2 phase. As the brazing temperature or holding time increased, τ 3 was gradually replaced by the B2 phase, and the Ti 2 Ni phase decreased and ultimately disappeared. The maximum shear strength achieved at room temperature was 318 MPa when the joint was brazed at 1180 °C for 20 min, whereas it was 278 MPa at 650 °C. Crack primarily propagated in the τ 3 compound, which was extremely hard and brittle, and partially traversed the B2 and O phases.