Microstructure Evolution of a Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y Alloy during Massive Transformation and Subsequent Annealing

Metals

Yong Xu¹  Jinshan Li²  Lin Song²  Chunqing Wang²  Tiebang Zhang²  Xiangyi Xue² 

[1] Nantong Elian Advanced Materials Science and Technology Ltd., Nantong 226399, China;State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China;

关键词: TiAl alloys;    phase transformation;    precipitation behavior;    electron microscopy;   

DOI  :  10.3390/met8020089

来源: DOAJ

【 摘 要 】

It has been widely reported that the microstructure refinement of TiAl alloys can be achieved by massive transformation and subsequent annealing in α2 + γ two phase field. To achieve this goal, several heat treatment parameters must be adjusted, including the heat treatment temperature around single α phase field, the annealing temperature, and the annealing time for the precipitation of α2 phase. Thus, a systematic study is needed for each alloy with different compositions. In this study, the heat treatment parameters for grain refinement via massive transformation of a high Nb-containing TiAl are investigated. Precipitation of α2 phase during annealing is observed by transmission electron microscopy. It is found that 30 min at single α phase field is appropriate for the massive transformation; a full, massively transformed microstructure cannot be obtained by oil or water quenching. A short annealing time can result in a refined microstructure, whereas the sizes of the precipitated α2 phase increases with the increase of annealing time. The α2 phase can form at the interface of twin boundaries of the γ phase, following the Blackburn orientation relationship with both sides. The Vickers hardness is measured for the annealed samples, which remains relatively stable for different annealing times.

【 授权许可】

Unknown