Experiment and modeling of TiB2/TiB boride layer of Ti-6Al-2Zr-1Mo-1V alloy
(1. Key Laboratory for Microstructural Control of Metallic Materials of Jiangxi Province, Nanchang Hangkong University, Nanchang 330063, China;
2. Beijing Institute of Aeronautical Materials, Beijing 100095, China)
2. Beijing Institute of Aeronautical Materials, Beijing 100095, China)
Abstract: The influence of the boriding conditions on the boride layers was examined by boriding Ti-6Al-2Zr- 1Mo-1V alloy in the temperature range of 920-1120 °C. The experimental results show that the boride layers were composed of a continuous thin outer layer of TiB2 and a thick inner layer of TiB with whiskers or needle-like morphologies that extended into the substrate. Thick and compact boride layers were obtained when the boriding temperatures were 1000-1080 °C, and the treatment time exceeded 8 h. The boride layer depth increased with the boriding temperature and time, and the growth kinetics of the boride layers was characterized by a parabolic curve. The growth kinetics of the boride layers, including both TiB2 and TiB layers, were predicted by establishing a diffusion model, which presented satisfactory consistency with the experimental data. As a result, the activation energies of boron in the TiB2 and TiB layers were estimated to be 223.1 and 246.9 kJ/mol, respectively.
Key words: Ti-6Al-2Zr-1Mo-1V alloy; boriding; microstructure; modeling