03. 07. 2017
Impurities in iron, nickel and aluminium reduce the cohesion of the material and can lead to catastrophic scenarios of the failure of metal constructions. An extensive synopsis of the theoretical and experimental knowledge, which arises from the long-term research of the scientists from the Institute of Physics of the CAS and Central European Institute of Technology CEITEC, was published by the prestigious journal Progress in Materials Science.
It is a journal with an impact factor of 31.083; in order, it is the third of 271 journals in the category Materials Science, Multidisciplinary, it is almost in the highest percentile (1.11 %) in this category. Publishing an article in a journal of this format is a great success. “The success is even more valuable by the fact that the Czech authorial team went without foreign capacity from a prestigious scientific institution that would notionally open the door for it,” states one of the authors, Prof. Pavel Lejček from the Institute of Physics of the CAS.
The low cohesion of the material can lead to an unexpected collapse of the metal construction, as happened at the Hinkley Point A power plant in 1969 when the turbine rotor was torn. “This so-called intergranular brittleness is caused by admixtures and trace elements, which can never be entirely removed in the production of the given components and which over time concentrate in places between the individual grains of the substance called grain boundaries,” explains the co-author of the publication, Prof. Mojmír Šob from the research group of the Synthesis and analysis of nanostructures of the CEITEC.
“The admixtures tend to accumulate at the grain boundaries at higher temperatures and change the bond ratios so that a significant reduction in cohesion of material and lightening breakage of the component can easily occur,” adds Prof. Lejček.
The team of professors Lejček and Šob has dealt with issue in the long term. It has already acquired a series of knowledge for instance on the magnetism of the grain boundaries or on the dependence of the segregation of the impurities on the orientation of the boundaries. The researchers dealt chiefly with theoretical modelling of the characteristics of the material and simulations of the structures at the Brno workplaces. The workplaces of the Czech Academy of Sciences then conduct particularly the experimental research.
In the published article, the authors summarized and critically evaluated the values of the segregation energy of a wide range of admixtures in iron, nickel and aluminium at the grain boundaries and on the surfaces of these materials. The scientists obtained these values based on their own calculations and experiments using data available in the literature. “With them, we evaluated under which conditions and with what methods they were determined and how trustworthy they were,” says Prof. Šob adding that the results of this basic research could be used for instance by experts, who deal with new possibilities of the treatment of metals. The methodology presented in the work can also be applied to other materials.
P. Lejček, M. Šob, V. Paidar: Interfacial segregation and grain boundary embrittlement: An overview and critical assessment of experimental data and calculated results. Progress in Materials Science 87 (2017) 83–139. Accessible at http://dx.doi.org/10.1016/j.pmatsci.2016.11.001
Prepared by: Leona Matušková, Division of the External Relations of the CAO of the CAS, utilizing materials of the Institute of Physics of the CAS and the article in CEITEC.
Photo: Pixabay, Institute of Physics of the CAS and CEITEC
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