期刊
ACTA MATERIALIA
卷 86, 期 -, 页码 374-384出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2014.11.046
关键词
Cementite; Diffraction; Iron alloys; First-principles calculations; Thermodynamic modeling
资金
- US Natural Science Foundation (NSF) [CMMI-1333999]
- Directorate For Engineering
- Div Of Civil, Mechanical, & Manufact Inn [1333999] Funding Source: National Science Foundation
New data are presented on the ambient-temperature values of the orthorhombic lattice parameters of cementite (theta, Fe3C1-z). The cementite was obtained by electrolytically etching away the ferrite or martensite from quenched dual-phase Fe-C alloys equilibrated at 823 K <= T <= 1323 K, i.e. in the a (ferrite) + theta or y (austenite) + theta two-phase fields, followed by quenching. In qualitative agreement with earlier data (Petch, 1944), the decrease in the lattice parameters a and c and the simultaneous increase in b with increasing equilibration temperature T can be attributed to an increase in the fraction of C vacancies, z, in Fe3C1-z in equilibrium with the corresponding Fe[C] terminal solid-solution phase (alpha or gamma). The experimental data are compared with results on C-vacancy-induced lattice-parameter changes obtained by first-principles calculations performed within the framework of density-functional theory (DFT). The anisotropy of the changes in the lattice parameters a, b and c predicted by DFT agrees qualitatively with the experimentally observed changes occurring with increasing equilibration temperature. Eventually, the equilibration-temperature dependence of the unit-cell volume of the cementite, V= abc, was used to calculate T-dependent values of the vacancy fraction z, thereby yielding data for the alpha + theta/theta and gamma + theta/theta phase boundaries in the metastable phase diagram of Fe-Fe3C. In particular, the alpha + theta/theta phase boundary determined could be interpreted in terms of Gibbs energy of C-vacancy formation in cementite, whereby its enthalpy contribution agrees well with the results of the first-principles calculations. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据