Diffusion processes during cementite precipitation and their impact on electrical and thermal conductivity of a heat-treatable steel
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- 作者：S. Klein ; L. Mujica Roncery ; M. Walter ; S. Weber…
- 刊名：Journal of Materials Science
- 出版年：2017
- 出版时间：January 2017
- 年：2017
- 卷：52
- 期：1
- 页码：375-390
- 全文大小：2,080 KB
- 刊物类别：Chemistry and Materials Science
- 刊物主题：Chemistry
Materials Science
Characterization and Evaluation Materials
Polymer Sciences
Continuum Mechanics and Mechanics of Materials
Crystallography
Mechanics - 出版者：Springer Netherlands
- ISSN：1573-4803
- 卷排序：52
文摘
The thermal conductivity of heat-treatable steels is highly dependent on their thermo-mechanical history and the alloying degree. Besides phase transformations like the martensitic \(\upgamma \rightarrow \upalpha ^{\prime }\) or the degree of deformation, the precipitation of carbides exerts a strong influence on the thermal conductivity of these steels. In the current work, thermal and electrical conductivity of a 0.45 mass% C steel is investigated during an isothermal heat treatment at 700 \(^{\circ }\)C and correlated with the precipitation kinetics of cementite. To include processes in the short-term as well as in the long-term range, annealing times from 1 s to 200 h are applied. This investigation includes microstructural characterization, diffusion simulations, and electrical and thermal conductivity measurements. The precipitation of carbides is connected with various microstructural processes which separately influence the thermophysical properties of the steel from the solution state to the short-term and long-term annealing states. In the early stages of cementite growth, an interstitial-dominated diffusion reaction takes place (carbon diffusion in the metastable condition of local equilibrium non-partitioning). Afterwards, substitutional-dominated diffusion controls the kinetics of the reaction. The electrical and thermal conductivity increase differently during the two stages of the carbide precipitation. The increment is associated to the binding of alloying elements into the carbides and to the reduction of the distortion of the martensitic matrix. Both factors increase the electron density and reduce the electron and phonon scattering. The correlation of the precipitation kinetics and the thermophysical properties are of general interest for the design of heat-treatable steels.