Effect of Brazing Temperature and Holding Time on the Interfacial Microstructure and Properties of TC4-Brazed Joints...

A TC4 alloy was joined with Ti-Zr-Cu-Ni amorphous filler by vacuum brazing. The paper further explored how different brazing temperatures with a 20 min holding time, or varying holding times at a brazing temperature of 900 °C, impact the interface width, microstructure, composition distribution, microhardness, shear strength, and fracture surface of the brazed joints. The findings indicated that as the brazing temperature increased, the interface width became wider. Moreover, as the brazing temperature continued to rise, both the size of the Widmanstätten structure and the amount of the (Ti, Zr)₂(Cu, Ni) brittle phase increased continuously, leading to the joint exhibiting harder and more brittle properties. As the temperature rose from 860 °C to 900 °C, the microhardness went up from 462.8 HV_0.1 to 482.6 HV_0.1. But when the temperature continued to increase (920 °C, 940 °C), the microhardness started to decrease, until it reached 392.6 HV_0.1 at a holding time of 20 min. As the brazing temperature increased, the width of the joint interface expanded, and the shear strength continued to rise. When the brazing temperature rose to 940 °C, the shear strength increased to 223.9 MPa under a holding time of 20 min. With the prolongation of the holding time (from 10 min to 30 min), the Widmanstätten structure at the joint interface continuously grew towards the center. Additionally, the (Ti, Zr)₂(Cu, Ni) phase and eutectic structure were separated by the Widmanstätten structure. The microhardness and shear strength reached their maximum values at 900 °C, and the shear strength was measured at 137.6 MPa.