Microstructural Evolution and Precipitation Mechanism of α-Phase in Ti-55531 Alloy Aged at High Temperature

Abstract:

After two-stage annealing heat treatment process, the near β-Titanium alloys reveal a mixed microstructure containing lath-like α phase and finer acicular α phase in β matrix, leading to the improvement of strength-ductility balance. In this paper, the microstructural evolution and the behaviour of α precipitate during high temperature ageing process were investigated by SEM in a near β-Titanium alloy called Ti-55531.The relationship between α precipitates and the β grain orientation in high temperature was investigated by EBSD. The results show that the α-phase precipitated only at some places of the β grain boundaries at higher ageing temperature (~780 °C); the amount of grain boundary α increased with the decreased of the ageing temperature; after ageing at 720 °C for 45 min, we found that the α-phase precipitated not only at grain boundaries but also within the grains. It seems that the precipitation of grain boundary α is strongly influenced by β grain boundary energy which means that grain boundary α tends to form preferentially at high energy grain boundaries (high-angle grain boundaries); The α-phase precipitates more easily at the grain boundaries where the {110} plane of adjacent β grains have the same orientation.

• Periodical: Materials Science Forum (Volumes 747-748)
• Pages: 912-918
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.747-748.912
• Online since: February 2013
• Authors: Xue Zhang, Yi Chen, Feng Shou Zhang, Jun Ting Yang, Yun Jin Lai, Hong Chao Kou, Jin Shan Li, Lian Zhou
• Keywords: EBSD, High Temperature Ageing, Ti-55531 Alloy, α-Phase Precipitate

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