Effect of joining temperature on Al2024/Ag/Ti-6Al-4V joints during transient liquid phase bonding

Abstract

The objective of this study is to investigate the effect of bonding temperature on the microstructure and mechanical properties of Al2024 and Ti-6Al-4V diffusion bonds using a 30 μm pure silver foil as interlayer. Using optical microscopy, scanning electron microscopy, line scan and X-ray diffraction, the interfaces of joints were evaluated. The mechanical properties of joints were measured using Vickers micro-hardness and shear strength. At the bonding temperature of 570°C joints contained a non-uniform distribution of elements and various intermetallic phases. With increasing bonding temperature, an uninterrupted microstructure is achieved. According to the results, liquid eutectic formed between Ag interlayer and Al2024, while solid-state diffusion occurs between the Ag interlayer and Ti-6Al-4V. The increase in bonding temperature from 570 to 580 °C resulted in higher shear strength, from 71 MPa to 121 MPa.