Interfacial Microstructure and Mechanical Property of TC4 / TNM Brazed Joints

Abstract:

Vacuum dissimilar brazing of TC4 alloy and TNM alloy was performed at 900 ~ 1020 °C for 10 min using amorphous Ti-25.65Zr-13.3Cu-12.35Ni-3Co-2Mo (wt.%) filler. The interfacial microstructure and formation mechanism of the TC4/TNM brazed joint and the variation of the interfacial microstructure and shear strength of the brazed joints as brazing temperature were systematically investigated. Results revealed that the interfacial microstructure of the TC4/TNM joints brazed at 900 ~ 980 ℃ were TC4/ fine basket weave (α+β)-Ti/γ-(Ti, Zr)2(Cu, Ni) + α-Ti/Ti3Al/TNM. The brittle γ-(Ti, Zr)2(Cu, Ni) decreases but the ductile α-Ti increases with brazing temperature. Once the brazing temperature increased to 1000 °C and 1020 °C, the interfacial reaction layer of the TC4/TNM brazed joints transformed from three layers into two layers, which consist of coarse acicular (α+β)-Ti with poor ductility and Ti3Al, respectively. And the coarse acicular (α+β)-Ti was further coarsened with brazing temperature. The shear strength of the TC4/TNM brazed joint increased first and then decreased with brazing temperature. The maximum shear strength of 494.83 MPa was obtained at 980 ℃. The brittle fracture primarily occurs in the brazing seam near TNM side regardless of brazing temperature during shear test.