New Approaches in Study of Inhomogeneity of Heterogeneous Structures

T. S. Skoblo, O. Yu. Klochko, E. L. Belkin, A. I. Sidashenko

Kharkiv Petro Vasylenko National Technical University of Agriculture, 44 Alchevskykh Str., 61002 Kharkiv, Ukraine

Received: 24.11.2017. Download: PDF

Our paper is concerned with the development and improvement of the new methods of study different structures formed in chromium-containing carbon alloys. The described methods allow predicting changes in the local heterogeneity of structural constituents because of different processing operations being realized. The application of new techniques also involves the use of faster operations in computer-based optical-mathematical evaluation of such parameters. Due to dissipation of energy because of the diffusion process and changes in the density of the analysed samples, we associate phase formation with the hydrodynamic processes. The used technique includes a computer analysis of the metallographic structure images and is based on hydrodynamic analogies using Navier–Stokes equations. The estimation is made based on the calculated values located on the analysed images digitized into the bmp format. As a result, the inhomogeneity of the high-chromium cast iron via the distribution of the dispersion degree of the conventional colour is estimated. Modelling of a local heterogeneity of the structural components is carried out. The modelling includes the new estimation parameters, $i.e.$, $M$-triples, which are an ordered set consisting of three real integers equal to divergence and Laplacian at the considered point on metallographic image; we express the energy dissipation power in terms of the $M$-triples. The simulation is carried out with the use of the $M$-triples’ invariant transformations when the metallographic image is rotated to different angles. The $M$-triple occurred to be a convenient parameter since it allows simulating changes of the local homogeneity in structural components by changing and varying the certain energy parameters (by rotation and permutation of the pixels on the image). The effect of heterogeneity of structural components on their hardness is evaluated via simulation. As determined, although the alloy hardness and dispersion increase proportionally, the impact of hardness along vertical and horizontal directions is lower than one in the case of angular rotation that indicates that the dispersity of the structural components does not exert a decisive effect on the alloy hardness. These results require more detailed analysis, which should include the role of other factors, such as the degree of dislocation-structure density, in particular, within the formed subgrain boundaries. Simulation of the angular rotation will then make it possible to carry out the closest correlation between all parameters that makes up the $M$-triples and to evaluate the structural components of heterogeneity as well as to reveal their formation features within the heterogeneous alloys. Our methodological approach and the obtained analysis results also allow evaluating the influence of various operative factors on the materials’ properties. Based on revealed anisotropy of the metal working-layer properties, it is recommended to evaluate the structure–properties connection over the transverse sections (across the dendrites’ axes) in the case of centrifugal casting as well.

Key words: metallographic image, invariant transformation, optical-mathematical analysis, chromium heterogeneous alloys, phase dispersion degree, structural heterogeneity, hardness.



PACS: 07.05.Pj, 61.72.Ff, 61.72.Mm, 81.05.Bx, 81.30.Mh, 81.40.Cd, 81.70.Fy

Citation: T. S. Skoblo, O. Yu. Klochko, E. L. Belkin, and A. I. Sidashenko, New Approaches in Study of Inhomogeneity of Heterogeneous Structures, Metallofiz. Noveishie Tekhnol., 40, No. 2: 255—280 (2018) (in Russian)

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