Effect of Ti on Microstructure and Properties of Tungsten Heavy Alloy Joint Brazed by CuAgTi Filler Metal.

In this paper, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffractometer (XRD) were used to comprehensively analyze the microstructure and brazing performance of a CuAgTi filler metal with braze tungsten heavy alloys. The association of microstructure, wettability and shear strength of brazing joints was also investigated. With the addition of Ti, the Ti₃Cu₄ phase appeared in the microstructure of filler metal. Ti is active element that promotes the reaction of filler with tungsten. Therefore, the Ti element is enriched around tungsten and forms a Ti₂Cu layer at the interface, leaving a Cu-rich/Ti-poor area on the side. Remaining Ti and Cu elements form the acicular Ti₃Cu₄ structure at the center of the brazing zone. The wettability of filler metal is improved, and the spreading area is increased from 120.3 mm² to 320.9 mm² with the addition of 10 wt.% Ti. The shear strength of joint reaches the highest level at a Ti content of 2.5 wt.%, the highest shear strength is 245.6 MPa at room temperature and 142.2 MPa at 400 °C.