Theoretical investigation of the omega-related phases in TiAl-Nb/Mo alloys

IMR OpenIR

	Theoretical investigation of the omega-related phases in TiAl-Nb/Mo alloys
	Q. M. Hu; L. Vitos; R. Yang
	2014
发表期刊	Physical Review B
ISSN	1098-0121
卷号	90 期号:5
摘要	The incorporation of cubic beta/beta(0) phase improves significantly the ductility and workability of TiAl-based alloys. However, the ductility deteriorates with the precipitation of the ordered hexagonal omega(0) phase in the beta/beta(0) phase. To avoid the formation of the omega(0) phase in alloy design, fundamentals about the beta/beta(0) to omega(0) phase transition and its alloying element dependence have to be known. In the present work, we investigated the phase transition and phase stability in Ti4Al3Nb and Ti4Al3Mo alloys using a first-principles method based on density functional theory. Our calculations indicate that for the beta(0) to omega(0) transition, the "collapse-diffusion" pathway is easier than the "diffusion-collapse" one; however, both pathways are quite difficult due to the high-energy barriers. The beta(0) to omega '' transition occurs through the "diffusion-collapse" pathway without an energy barrier (except for the activation energy for the short-range diffusion needed for atomic rearrangement). Comparing the total energies of different phases, we find that the omega(0) phase of Ti4Al3Nb is more stable than beta(0) and vice versa for Ti4Al3Mo whereas the relative stability of omega '' to beta(0) for Ti4Al3Nb is stronger than that for Ti4Al3Mo, indicating that the addition of Mo inhibits the transition from the beta(0)- to the omega-related phases in Ti4Al3Nb. Our calculations demonstrate that omega '' is more stable than omega(0) for both Ti4Al3Nb and Ti4Al3Mo, in contrast to the previously proposed picture based on some experimental observations, the possible origins of which are discussed in detail.
部门归属	[hu, qing-miao ; yang, rui] chinese acad sci, inst met res, shenyang natl lab mat sci, shenyang 110016, peoples r china. [vitos, levente] royal inst technol, dept mat sci & engn, se-10044 stockholm, sweden. ; yang, r (reprint author), chinese acad sci, inst met res, shenyang natl lab mat sci, 72 wenhua rd, shenyang 110016, peoples r china. ; ryang@imr.ac.cn
关键词	Total-energy Calculations Quasi-random Structures Wave Basis-set 1st-principles Calculations Potential Model Stability Metals Transformations Approximation Aluminides
URL	查看原文
语种	英语
文献类型	期刊论文
条目标识符	http://ir.imr.ac.cn/handle/321006/73241
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	Q. M. Hu,L. Vitos,R. Yang. Theoretical investigation of the omega-related phases in TiAl-Nb/Mo alloys[J]. Physical Review B,2014,90(5).
APA	Q. M. Hu,L. Vitos,&R. Yang.(2014).Theoretical investigation of the omega-related phases in TiAl-Nb/Mo alloys.Physical Review B,90(5).
MLA	Q. M. Hu,et al."Theoretical investigation of the omega-related phases in TiAl-Nb/Mo alloys".Physical Review B 90.5(2014).