Microstructure and mechanical properties of TiZrHfNbMo high-entropy alloy and Ti-based composites brazed joint

Abstract

TiZrHfNbMo high-entropy alloy and titanium matrix composite were vacuum brazed using carbon nanotubes reinforced AgCuTi composite filler. Microstructure and mechanical properties of the joints were systematically studied by X-ray diffractometer, scanning electron microscopy, energy spectrum and universal testing machine. The results show that the joints brazed at different temperatures from 820 °C to 910 °C for 15 min are successfully connected. The microstructure of the joint is composed of Ag(s,s), Cu(s,s), Ti(s,s), CuTi, ZrCu and CuTi2, the base material elements are fully diffused in the joint. When the brazing holding time is fixed, the shear strength of the joint at room temperature increases first and then decreases with the increase of brazing temperature. The formation of a certain amount of Ti-Cu intermetallic compounds widens the thickness of the reaction layer and improves the strength of the joint, while the formation of excessive Ti-Cu intermetallic compounds weakens the joint ability to relieve stress through plastic deformation, leading to a significant reduction in the joint strength. The best welded joint is obtained when the brazing temperature is 850 ℃ and the holding time is 15 min. The shear strength is up to 146 MPa, and the fracture mode of the shear fracture of the joint is brittle fracture.

Keywords

• high-entropy alloy
• titanium matrix composite
• brazing
• shear strength