In this study, dilatometry and metallography were used to investigate the effect of silicon and copper alloying on the decomposition kinetics of 54SiCr6 steel during continuous slow cooling. It is different from the published literature for using the approach of the local activation energy of the austenite decomposition Ef and the local Avrami exponent n of the volume fraction of the transformed phase f to study the kinetics of austenite-pearlitic transformation in cooled 54SiCr steel at slow cooling rates. The Johnson-Mehl-Avrami equation was used to determine the dependence of the local activation energy for austenite decomposition Ef and the local Avrami exponent n on the volume fraction of the transformed phase f. The mechanism of the austenite decomposition was analysed based on the calculated values of n. Both the local and average activation energies were used to evaluate the alloying effect, and the results were compared with those obtained from other methods. The type of microstructure formed as a result of cooling at rates of 0.5 K/s, 0.3 K/s, 0.1 K/s and 0.05 K/s was determined. The effects of changes in the cooling rate and the content of silicon (1.5-2.5 wt.%) and copper (0.12-1.47 wt.%) on the dimension of nucleation and growth kinetics of the transformed phase were studied. It was revealed that the pearlite microstructure was formed predominantly in 54SiCr6 steel as a result of continuous cooling at slow cooling rates. It was also found that alloying this steel with copper led to a significant decrease in the value of Ef, as well as to a change in the mechanism of the kinetics of the austenite-pearlite transformation, which was realised in predominantly two- and three-dimensional nucleation and growth at a constant nucleation rate. At the same time, alloying this steel with silicon led only to a slight change in Ef. The results of the study of 54SiCr steel presented the dependence of the activation energy of transformation and the local Avrami exponent on the volume fraction of the transformed phase at a given cooling rate at different copper and silicon contents. In addition, the study provides insight into the mechanism of kinetics in cooled 54SiCr steel as a function of the cooling rate.

COMTES FHT a s Prumyslova 995 334 41 Dobrany Czech Republic

Department of Physics South Ukrainian National Pedagogical University Staroprotfrankivska 26 65020 Odessa Ukraine

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Chen K., Jiang Z., Liu F., Yu J., Li Y., Gong W., Chen C. Effect of quenching and tempering temperature on microstructure and tensile properties of microalloyed ultra-high strength suspension spring steel. Mater. Sci. Eng. A. 2019;766:138272. doi: 10.1016/j.msea.2019.138272. DOI

Nam W.-J., Choi H.-C. Effects of silicon, nickel, and vanadium on impact toughness in spring steels. Mater. Sci. Technol. 1997;13:568–574. doi: 10.1179/mst.1997.13.7.568. DOI

Teramoto S., Imura M., Masuda Y., Ishida T., Ohnuma M., Neishi Y., Suzuki T. Influence of Iron Carbide on Mechanical Properties in High Silicon-Added Medium-Carbon Martensitic Steels. ISIJ Int. 2020;60:182–189. doi: 10.2355/isijinternational.ISIJINT-2019-331. DOI

Suzuki T., Kozawa S., Yoshioka T., Kobuta M., Miyamoto A. Low Alloyed High Strength Suspension Spring Steel. Nippon Technical Report 2019.

Podgornik B., Leskovšek V., Godec M., Senčič B. Microstructure refinement and its effect on properties of spring steel. Mater. Sci. Eng. A. 2014;599:81–86. doi: 10.1016/j.msea.2014.01.054. DOI

Hawbolt E.B., Chau B., Brimacombe J.K. Kinetics of austenite-pearlite transformation in eutectoid carbon steel. Metall. Trans. A. 1983;14:1803–1815. doi: 10.1007/BF02645550. DOI

Hawbolt E.B., Chau B., Brimacombe J.K. Kinetics of austenite-ferrite and austenite-pearlite transformations in a 1025 carbon steel. Metall. Trans. A. 1985;16:565–578. doi: 10.1007/BF02814230. DOI

Li H., Gai K., He L., Zhang C., Cui H., Li M. Non-isothermal phase-transformation kinetics model for evaluating the austenization of 55CrMo steel based on Johnson–Mehl–Avrami equation. Mater. Des. 2016;92:731–741. doi: 10.1016/j.matdes.2015.12.110. DOI

Liu X., Li H., Zhan M. A review on the modeling and simulations of solid-state diffusional phase transformations in metals and alloys. Manuf. Rev. 2018;5:10. doi: 10.1051/mfreview/2018008. DOI

Calka A., Radliński A.P. Decoupled bulk and surface crystallization in Pd 85 Si 15 glassy metallic alloys: Description of isothermal crystallization by a local value of the Avrami exponent. J. Mater. Res. 1988;3:59–66. doi: 10.1557/JMR.1988.0059. DOI

Lu W., Yan B., Huang W. Complex primary crystallization kinetics of amorphous Finemet alloy. J. Non. Cryst. Solids. 2005;351:3320–3324. doi: 10.1016/j.jnoncrysol.2005.08.018. DOI

Zheng Y.-F., Wu R.-M., Li X.-C., Wu X.-C. Continuous cooling transformation behaviour and bainite formation kinetics of new bainitic steel. Mater. Sci. Technol. 2017;33:454–463. doi: 10.1080/02670836.2016.1224608. DOI

Song W., Lei M., Wan M., Huang C. Continuous Cooling Transformation Behaviour and Bainite Transformation Kinetics of 23CrNi3Mo Carburised Steel. Metals. 2020;11:48. doi: 10.3390/met11010048. DOI

Dlouhy J., Hauserova D., Novy Z. Influence of the carbide-particle spheroidisation process on the microstructure after the quenching and annealing of 100CrMnSi6-4 bearing steel. Mater. Tehnol. 2016;50:159–162. doi: 10.17222/mit.2014.303. DOI

Kotous J., Dlouhy J., Nachazelova D., Hradil D. Accelerated Carbide Spheroidisation and Refinement in Spring Steel 54SiCr6. IOP Conf. Ser. Mater. Sci. Eng. 2018;461:012044. doi: 10.1088/1757-899X/461/1/012044. DOI

Salvetr P., Nový Z., Gokhman A., Kotous J., Zmeko J., Motyčka P., Dlouhý J. Influence of Si and Cu content on tempering and properties of 54SiCr6 steel. Manuf. Technol. 2020;20:516–520. doi: 10.21062/mft.2020.079. DOI

Gokhman A., Nový Z., Salvetr P., Ryukhtin V., Strunz P., Motyčka P., Zmeko J., Kotous J. Effects of Silicon, Chromium, and Copper on Kinetic Parameters of Precipitation during Tempering of Medium Carbon Steels. Materials. 2021;14:1445. doi: 10.3390/ma14061445. PubMed DOI PMC

Salvetr P., Gokhman A., Nový Z., Motyčka P., Kotous J. Effect of 1.5 wt% Copper Addition and Various Contents of Silicon on Mechanical Properties of 1.7102 Medium Carbon Steel. Materials. 2021;14:5244. doi: 10.3390/ma14185244. PubMed DOI PMC

Nový Z., Salvetr P., Kotous J., Motyčka P., Gokhman A., Donik Č., Džugan J. Enhanced Spring Steel’s Strength Using Strain Assisted Tempering. Materials. 2022;15:7354. doi: 10.3390/ma15207354. PubMed DOI PMC

Salvetr P., Gokhman A., Svoboda M., Donik Č., Podstranská I., Kotous J., Nový Z. Effect of Cu Alloying on Mechanical Properties of Medium-C Steel after Long-Time Tempering at 500 °C. Materials. 2023;16:2390. doi: 10.3390/ma16062390. PubMed DOI PMC

Geissler J., Mesplont C., Vandeputte S., De Cooman B.C. Dilatometric study of the effect of soluble boron on the continuous and isothermal austenite decomposition in 0.15C–1.6Mn steel. Int. J. Mater. Res. 2022;93:1108–1118. doi: 10.1515/ijmr-2002-0191. DOI

Ranganathan S., Von Heimendahl M. The three activation energies with isothermal transformations: Applications to metallic glasses. J. Mater. Sci. 1981;16:2401–2404. doi: 10.1007/BF01113575. DOI

Gupta C., Dey G.K., Chakravartty J.K., Srivastav D., Banerjee S. A study of bainite transformation in a new CrMoV steel under continuous cooling conditions. Scr. Mater. 2005;53:559–564. doi: 10.1016/j.scriptamat.2005.04.031. DOI

Cardoso R.A., de Faria G.L. Characterization of Austenite Decomposition in Steels with Different Chemical Concepts and High Potential to Manufacture Seamed Pipes for Oil and Gas Industry. Mater. Res. 2019;22:e20190378. doi: 10.1590/1980-5373-mr-2019-0378. DOI

Kaputkin D.E. Correlation between the thermokinetics parameters of diffusional decomposition and the activation energy of diffusion in steels and nonferrous alloys. Phys. Met. Metallogr. 2005;99:343–347.

Bhadeshia H.K.D.H. Diffusion of carbon in austenite. Met. Sci. 1981;15:477–480. doi: 10.1179/030634581790426525. DOI

Kaufman L., Radcliffe S.V., Cohen M. Decomposition of Austenite by Diffusional Processes. Interscience; New York, NY, USA: 1962. pp. 313–352.

Kennelly J. The Effect of Copper on Carbon Diffusivity in PremoMet® Alloy. Drexel University; Philadelphia, PA, USA: 2014.