Abstract
Grain boundary character and microstructural evolution during hot deformation of a high Nb-containing TiAl alloy with the composition of Ti-45Al-8.5Nb-(W, B, Y) was investigated. The plasma arc-melted alloy exhibits nearly lamellar microstructures with β/B2 phase precipitates along colony boundaries. The retained β/B2 phase rich in Ti, Nb and W and poor in Al is formed by the β→α transformation during nonequilibrium solidification. This β/B2 precipitation is caused by the high cooling rate, low atom diffusion rate of β stabilizers and different partition coefficients of the elements. B and Y elements exist mainly as borides and Y 2 O 3 , respectively. The morphology, size, composition and stability of β/B2 phase are determined by hot deformation. The high temperature and press enhance the elements diffusion, and thus the variation of the composition of β/B2 phase in deformed samples is obviously observed. When the samples are deformed in (α + γ) phase region, the transformation β/B2→α 2 takes place. Considering the different crystal structures of β/B2 and α 2 phases, there is a tendency for β/B2 phase to transform to a more closed packed structure of α 2 during deformation. The β/B2→ α 2 transformation is promoted by the hot deformation.
| Translated title of the contribution | 高Nb-TiAl 热变形过程中的晶界特征和显微组织演化 |
|---|---|
| Original language | English |
| Pages (from-to) | 2927-2935 |
| Number of pages | 9 |
| Journal | Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering |
| Volume | 47 |
| Issue number | 10 |
| State | Published - 1 Oct 2018 |
Keywords
- Grain character
- Hot deformation
- Microsegregation
- Microstructural evolution
- TiAl