Effects of TiZn3 and TiZn16 components on the microstructure and mechanical performance of Ti-6Al-4 V alloy joints formed via ultrasonic assisted brazing using pre-galvanized workpieces

Yinan Li; Zhuang Cui; Hongchang Zhang; Zilong Peng; Jiuchun Yan; Binjiang Lv; Ning Cui

doi:10.1016/j.ultras.2022.106782

Effects of TiZn₃ and TiZn₁₆ components on the microstructure and mechanical performance of Ti-6Al-4 V alloy joints formed via ultrasonic assisted brazing using pre-galvanized workpieces

Ultrasonics. 2022 Sep:125:106782. doi: 10.1016/j.ultras.2022.106782. Epub 2022 Jun 4.

Authors

Yinan Li¹, Zhuang Cui¹, Hongchang Zhang¹, Zilong Peng¹, Jiuchun Yan², Binjiang Lv¹, Ning Cui¹

Affiliations

¹ School of Mechanical & Automotive Engineering, Qingdao University of Technology, Qingdao 266000, China.
² State Key Laboratory of Welding and Joining, Harbin Institute of Technology, Harbin 150001, China.

PMID: 35709574
DOI: 10.1016/j.ultras.2022.106782

Abstract

While the use of a Zn interlayer has been demonstrated to reduce the temperature required for joining easily oxidized metal alloys in atmospheric environments, the effects of reactions between the titanium alloy workpieces and the Zn interlayer on the mechanical performance of the finished joints are poorly understood. The present work addresses this issue by evaluating the chemical compositions at the interfaces of pre-galvanized Ti-6Al-4 V alloys joined at 420 °C in an atmospheric environment by ultrasonic-assisted brazing, and relating the observed compositions to the mechanical performances of the joints. The Ti-6Al-4 V alloy workpieces are first wetted by pure Zn using an ultrasonic assisted hot dip galvanizing (U-HDG). The obtained ultrasonic excitations are demonstrated to destroy the oxide film on the surfaces of the Ti-6Al-4 V workpieces and promote reactions between Ti and Zn at the interfaces. The plating of Zn on the workpiece surfaces is demonstrated to be realized by the formation of intermetallic compounds (IMCs) comprising a uniform TiZn₃ layer in contact with the Ti-6Al-4 V surface, followed by a mixed TiZn₃ + TiZn₁₆ layer and a η-Zn layer at the outer surface. Application of the ultrasonic-assisted brazing process is demonstrated to maintain uniform TiZn₃ layers next to the Ti-6Al-4 V surfaces, while the concentration of the TiZn₁₆ phase near the midpoint of the joints increases with increasing ultrasonic treatment time (UST) from 5 s to 20 s, and the corresponding concentration of the η-Zn phase decreases. The results of mechanical testing demonstrate that the shear strength of the joint obtained with a TiZn₃ layer thickness of 8-12 μm and a UST of 10 s is 210 MPa, which is 3.55 times greater than that obtained for joints processed without pre-galvanization.

Keywords: Brazing; Hot dip galvanizing; Mechanical performance; Microstructure; Simulation; Ti-6Al-4V; Ultrasonic.