中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 24 No. 10 October 2014 |
（1. State Key Laboratory for Advanced Metals and Materials,
University of Science and Technology Beijing, Beijing 100083, China;
2. National Center for Materials Service Safety,
University of Science and Technology Beijing, Beijing 100083, China）
Abstract:Microstructure instabilities of the fully lamellar Ti-45Al-8.5Nb-(W,B,Y) alloy were investigated by SEM and TEM after long-term thermal cycling (500 and 1000 thermal cycles) at 900 °C. Two major categories of microstructure instability were produced in the alloy after the thermal cycling: 1) The discontinuous coarsening implies that grain boundary migrations are inclined to occur in the Al-segregation region after the long-term thermal cycling, especially after 1000 thermal cycles. Al-segregation can be reduced during the process of long-term thermal cycling as a result of element diffusion; 2) The α2 lamellae become thinner and are broken after 1000 thermal cycles caused by the dissolution of α2 lamellae through phase transformation of α2→γ. The γ grains nucleate within the α2 lamellae or (α2+γ) lamellae in a random direction.
Key words: TiAl alloys; thermal cycling; thermal stability; discontinuous coarsening
