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Metal Science and Physics of Metals
ArticleName The mechanism of plastic deformation of graphite inclusions in high-strength cast iron during metal forming
DOI 10.17580/chm.2023.06.08
ArticleAuthor A. I. Pokrovsky

Physical and Technical Institute of the National Academy of Sciences of Belarus, Minsk, Republic of Belarus:
A. I. Pokrovsky, Cand. Eng., Associate Professor, Head of the Laboratory of High Pressures and Special Alloys, e-mail:


The goal of this work is to investigate the microstructure, fractograms and morphology of graphite inclusions in ductile cast iron, to prove their plastic flow and to propose a mechanism of plastic deformation of spherical graphite inclusions during pressure forming. Fractographic studies revealed two different morphological types of inclusions after hot forming: the central core and the tail part, which differ in strength. Scanning electron microscope studies of the surface of deformed cast iron after electroetching permitted evaluating the shape and morphology of graphite inclusions and prove their integrity. A two-stage mechanism of plastic deformation of graphite inclusions is proposed. At the first stage, which applies to a reduction ratio of up to 50%, only the outer layers (flakes) of the graphite inclusion are involved in the deformation process. Layer-by-layer exfoliation of flakes occurs exclusively from the surface of the spherulite. The inner core retains a radial-sectoral structure. At a reduction ratio above 60%, at first the above described process occurs, which is accompanied by displacement of the scales into tail protrusions. At the second stage of deformation, the mechanism changes dramatically. It consists in sliding of prismatic sectors (blocks) of graphite relative to each other, wedging out of the central ones from those sectors of the sphere that are located along the application of the load. At the same time, transverse sectors move closer to each other. Since the deformation process takes place at a high temperature, about 950 °С, and is very short, lasting about 1 s, then, after the completion of deformation, interatomic bonds are restored along the shortest interatomic distances, and the inclusion retains its integrity.
The work was carried out at the Physical and Technical Institute of the National Academy of Sciences of Belarus (Minsk) within the framework of the State Scientific Research Institute "Metallurgy", task No. 2.01.

keywords Ductile cast iron, casting, hot plastic deformation, microstructure, graphite inclusions, internal structure and morphology of inclusions

1. Pero-Sanz Elorz J. A., Fernández González D., Verdeja L. F. Physical Metallurgy of Cast Irons, Springer. 2018. 343 р.
2. Artola G., Monzón A., Lacaze J., Sertucha J. Tensile properties and fracture toughness at service temperatures of an optimized pearlitic ductile iron alloy for automotive crankshafts. Materials Science and Engineering. 2022. A831. 142206.
3. Mussa A., Krakhmalev P., Bergstrom J. Wear mechanisms and wear resistance of austempered ductile iron in reciprocal sliding contact. Wear. 2022. Vol. 498-499. 204305.
4. Liu C., Du Y., Ying T., Zhang L., Zhang X., Wang X., Yan G., Jiang B. Effects of graphite nodule count on mechanical properties and thermal conductivity of ductile iron. Materials Today Communications. 2022. Vol. 31. 103522.
5. Wigger T., Andriollo T., Xu C., Clark S. J., Gong Z., Atwood R. C., Hattel J. H., Tiedje N. S., Lee P. D., Azeem M. A. In situ synchrotron investigation of degenerate graphite nodule evolution in ductile cast iron. Acta Materialia. 2021. Vol. 221. 117367.
6. Benedetti M., Fontanari V., Lusuardi D. Effect of graphite morphology on the fatigue and fracture resistance of ferritic ductile cast iron. Engineering Fracture Mechanics. 2019. Vol. 206. pp. 427–441.
7. Zanardi F., Mapelli C., Barella S. Reclassification of spheroidal graphite ductile cast irons grades according to design needs. International Journal of Metalcasting. 2020. Vol. 14, Iss. 3. pp. 622–655.
8. Tewary U., Paul D., Mehtani H. K., Bhagavath S., Alankar A., Mohapatra G., Sahay S. S., Panwar A. S., Karagadde S., Samajdar I. The origin of graphite morphology in cast iron. Acta Materialia. 2022. Vol. 226. 117660.
9. Qing J., Lekakh S., Xu M., Field D. Formation of complex nuclei in graphite nodules of cast iron. Carbon. 2021. Vol. 171. pp. 276–288.
10. Stefanescu D. M., Alonso G., Suarez R. Recent developments in understanding nucleation and crystallization of spheroidal graphite in iron-carbon-silicon alloys. Metals. 2020. Vol. 10. 221.
11. Riposan I., Chisamera M., Stan S. The role of compounds in graphite formation in cast iron – A review. Materials Science Forum. 2018. Vol. 925 (3). pp. 3–11.
12. Ivanov V. G., Pirozhkova V. P., Lunev V. V. Study of the structure and formation of nodular graphite inclusions in ductile cast iron. Vostochno-Evropeyskiy zhurnal peredovykh tekhnologiy. 2016. Vol. 3. No. 5 (81). pp. 31–36.
13. Naydek V. L., Vekhovlyuk А. М. Some reflections on the mechanism of nodular graphite formation in cast iron. Protsessy litya. 2014. No. 1 (103). pp. 47–54.
14. Naydek V. L., Neizhko I. G., Gavrilyuk V. P. Nodular graphite in cast irons. Protsessy litya. 2012. No. 5 (95). pp. 33–42.
15. Chaus A. S., Sojka J., Pokrovskii A. I. Effect of hot plastic deformation on microstructural changes in cast iron with globular graphite. The Physics of Metals and Metallography. 2013. Vol. 114. No. 1. pp. 85–94.
16. Chaus A. S., Čaplovič L., Pokrovskii A. I., Sobota R. Microstructure and properties evaluation of ductile cast iron subjected to hot plastic deformation and ambient temperature compression. Archives of Metallurgy and Materials. 2023. Vol. 68. No. 2. рp. 639–648.
17. Pokrovskii A. I. Plastic flow of cementite and graphite impurities at processing by cast iron pressure. Litiyo i Metallurgiya. 2013. Vol. 69. No. 1, pp. 88–95.
18. Pokrovskii A. I. Features of structure formation of graphite inclusions at casting and hot plastic deformation. Chernye metally. 2023. No. 4. pp. 8–15.
19. Kostikov V. I., Varenkov A. N. Super-high-temperature composite materials. Moscow : Intermet Inzhiniring. 2003. 560 p.
20. Martens Kh. E. Graphite as a high-temperature material. Translated from English. Moscow : Mir. 1964. p. 139–174.

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