Crystallographic orientation evolution during the development of tri-modal microstructure in the hot working of TA15 titanium alloy

Pengfei Gao, Yang Cai, Mei Zhan, Xiaoguang Fan, Zhenni Lei

科研成果: 期刊稿件文章同行评审

53 引用 (Scopus)

摘要

The crystallographic orientation evolution and its dependence on processing parameters during the development of tri-modal microstructure of titanium alloy were studied by the thermal-mechanical processing tests and electron backscatter diffraction (EBSD) examination. It is found that the development of tri-modal microstructure undergoes two stages: firstly, bimodal microstructure consisting of equiaxed α (αp) and transformed β matrix (βt: a mix of secondary α phase (αs) and β phase) is formed after first-stage near-β forging; then, the tri-modal microstructure consisting of αp, lamellar α phase (αl) and βt are obtained after the following heat treatment. The equiaxed α in final tri-modal microstructure does not follow the Burgers orientation relationship (OR) with β phase. Its crystallographic orientation is hardly influenced by the hot processing parameters. The lamellar α in tri-modal microstructure is right the undissolved secondary α of bimodal microstructure (obtained after first step) during the heating process of the second step. Both of them keep the Burgers OR with β phase, however, the dissolution of secondary α present selectivity to some extent making the variant selection degree of lamellar α greater than that of secondary α. The variant selection degree of lamellar α in tri-modal microstructure decreases with increasing the cooling rate, deformation degree and strain rate of near-β forging. The secondary α in tri-modal microstructure is precipitated from β phase and obeys the Burgers OR with β phase during the cooling process of the second step. The existing lamellar α plays a strengthening role in the variant selection during its precipitation. While the cooling rate, deformation degree and strain rate of near-β forging show limited effect on the probabilities of each type of misorientation and variant selection degree of secondary α.

源语言英语
页(从-至)734-745
页数12
期刊Journal of Alloys and Compounds
741
DOI
出版状态已出版 - 15 4月 2018

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