Analysis of the interfacial microstructure, phase transformation, and diffusion mechanism of Ti2AlNb/TA2 joint diffusion-bonded at low temperature

• Published in: Materials characterization Vol. 209; p. 113732
• Main Authors: Chen, Yuqing, Cheng, Yuansheng, Zhao, Chunzhi, Zhan, Liqiang, Zhou, Tongxu, Wang, Guofeng
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-03-2024
• Subjects: Diffusion bonding; Solid-state interfacial reaction; Ternary interdiffusion coefficients; Ti2AlNb-based alloy; Ti2AlNb-based alloy; Solid-state interfacial reaction; Diffusion bonding; Ternary interdiffusion coefficients
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2024.113732

Ti2AlNb-based alloys are mostly diffusion-bonded with conventional titanium alloy at a high temperature of above 920 °C. However, the high temperature could reduce the mechanical properties of the matrix alloy, especially the significant decrease in ductility. Therefore, trying to lower the temperature of the hot process of Ti2AlNb-based alloy is a work worth exploring. The microstructure evolution of the Ti2AlNb-based alloy and the conventional titanium during the bonding process at low temperatures has not been analyzed in detail. In this work, Ti2AlNb-based alloy is diffusion-bonded with TA2 titanium at a low temperature of 800 °C under the pressure of 10 MPa for 1 h. The detailed microstructure and phase transformation of the dissimilar joint are analyzed to reveal the interface reaction during the diffusion process. The ternary interdiffusion coefficients of the TA2/Ti2AlNb alloys diffusion couple are calculated to detect the diffusion behavior and mechanism of different elements at the low temperature of 800 °C. The result shows that the interfacial reaction phases are Al-rich α phase / Nb-rich β + ω phase / tiny α phase / striped α2 phase / β/B2 + O + α2 phase respectively from the TA2 titanium (α phase) matrix to the Ti2AlNb-based alloy (β/B2 + O phase). The interdiffusion coefficients obtained suggest that the diffusion rate of Al is higher than that of Ti, while Ti diffuses faster than Nb. Additionally, it was observed that Ti facilitates the diffusion of Al and hinders the diffusion of Nb. On the other hand, both Al and Nb impede the diffusion of Ti in the TA2/Ti2AlNb alloy diffusion couple during the 800 °C diffusion process.
•The diffusion reaction of the Ti2AlNb/TA2 joint at a low temperature of 800 °C is dissected in detail.•The microstructure, phase transformation, interface, and mechanical properties are carefully investigated.•The ω phase is generated in the joint diffusion-bonded with Ti2AlNb-based alloy and conventional titanium.•The ternary interdiffusion coefficients of the Ti2AlNb/TA2 diffusion couple are calculated for the first time.