A method has been developed for studying the distribution of crystallite boundaries in materials with an ultrafine-grained structure.

Quantitative characterization of intercrystalline boundaries in austenitic stainless steel with an ultrafine-grained structure using cluster analysis

Senior Researcher, Laboratory of Physical Mesomechanics and Non-Destructive Testing Methods, Institute of Physics and Mathematics of the Siberian Branch of the Russian Academy of Sciences P.V. Kuznetsov. together with colleagues from the Institute of Physics and Mathematics, Ural Branch of the Russian Academy of Sciences (Ekaterinburg) and TSUSU, they developed a method for studying the distributions of crystallite boundaries in materials with an ultrafine-grained structure by energy, measured by the method of grain-boundary etching grooves using a scanning tunneling microscope. The measured energy boundary distributions are considered as a superposition of individual distributions (populations), each of which has its own value of average energy, variance and share in the overall distribution. The characteristics of each population can be isolated from the general distribution using a special developed algorithm - cluster analysis, based on statistical criteria. The method was tested on the example of austenitic stainless steel 12Kh15G9ND with different structural states:

a) initial coarse-crystalline structure;

b) ultra-fine-grained structure obtained by hot transverse helical rolling;

c) ultra-fine-grained structure obtained by hot transverse helical rolling and additional cold rolling.

Cluster analysis showed that the number of boundary populations and their main characteristics naturally change depending on the structure of the steel.

The results of cluster analysis of experimental distributions are compared with data from measuring the distributions of crystallite boundaries along misorientations using the electron backscatter diffraction method. The agreement and discrepancy between the results of cluster analysis of energy distributions of crystallite boundaries and misorientation distributions are discussed taking into account the difference in the nature of the data obtained.

Description of experimental energy distributions of grain boundaries using the cluster analysis method for steel: in the initial state; after warm PVP; after additional cold rolling

The work was carried out within the framework of the state assignment of the Institute of Applied Physics and Mathematics of the Siberian Branch of the Russian Academy of Sciences, project FWRW-2021-0009 and the state assignment of the Ministry of Education and Science of the Russian Federation, topic “Function” No. 122021000035-6.

The research results were published in the journal "Physical Mesomechanics" (IF 1.6; Q2 in the Condensed Matter Physics category).

Kuznetsov, P.V., Stolbovsky, A.V. & Belyaeva, I.V. Quantitative Characterization of Grain Boundaries in Ultrafine-Grained Austenitic Stainless Steel by Cluster Analysis. Phys Mesomech 26, 415-433 (2023).
https://doi.org/10.1134/S1029959923040045.