Thermal Mechanism of The Influence of Laser Radiation on the Pores in the Surface Layer of Metallic Alloys

Purpose. Selective laser treatment is a promising method for creation the mechanical properties of the surface layer of metal alloys. The selectivity of laser processing is manifested in the predominant effect of the shock wave and the heat front on the defective areas. As a result, mechanical stress relaxation processes occur in the defective areas, while the defect-free material does not undergo significant changes. This makes it possible to improve the mechanical characteristics of the material while maintaining its initial structural state as a whole. Further development of the method of selective laser processing requires investigation the thermal mechanism of the effect of laser radiation on defective areas. The aim of the work is to investigate the interaction of the thermal front initiated by a laser pulse with defects in the surface layer of a metal alloy.

Methods. The propagation of a thermal front in the surface layer of a titanium alloy containing a pore system was studied by the finite difference method and using computer modeling.

Results. A model of the interaction of the heat front with a system of three pores located parallel to the sample surface is proposed. The developed model can be used to identify the specifics of the interaction of the heating wave with various defects. The specificity of the thermal mechanism of the effect of short-pulse laser radiation on the pores in the surface layer of metal alloys is manifested in the distortion of the thermal front and the non-uniform heating of the material.

Conclusion. The non-uniform heating of the material manifests itself, first of all, in the defective areas and can lead to stress relaxation due to plastic deformation of the heated material. The available experimental data obtained on samples subjected to selective laser treatment indicate a simultaneous increase in the microhardness of the surface layer and resistance to crack formation in condition of local loading conditions.

1. Dowden J., Schulz W. The theory of laser materials processing. heat and mass transfer in modern technology. Second ed. Cham, Springer Series in Materials Science, 2017. 432 p. https://doi.org/10.1007/978-3-319-56711-2.

2. Kaputkin D. E., Duradji V. N., Kaputkina N. A. Uskorennoye diffuzionnoye nasyshcheniye poverkhnosti metallov pri elektro-khimiko-termicheskoy obrabotke [Accelerated diffusion saturation of the metal surface during electro-chemical-thermal treatment]. Fizika i khimiya obrabotki materialov = Physics and chemistry of materials processing, 2020, no. 2, pp. 48–57. https://doi.org/10.30791/0015-3214-2020-2-48-57.

3. Stepanov M.S., Davidyan L.V., Dombrovsky Yu.M. Struktura, fazovyy sostav i svoystva stali posle mikrodugovogo borokhromirovaniya i boromolibdenirovaniya [Structure, phase composition and properties of steel after microarc boron chromium plating and boron molybdenum plating]. Izvestiya Volgogradskogo gosudarstvennogo tekhnicheskogo universiteta = Bulletin of the Volgograd State Technical University, 2018, no. 3 (213), pp. 124–131.

4. Krylova S. E., Oplesnin S. P., Manakov N. A., Yasakov A. S., Strizhov A. O. Vliyaniye tekhnologicheskikh parametrov gazoporoshkovoy lazernoy naplavki na strukturnyye kharakteristiki vosstanovlennogo poverkhnostnogo sloya korozionnostoykikh staley [Influence of technological parameters of gas-powder laser surfacing on the structural characteristics of the restored surface layer of corrosion-resistant steels]. Metallovedeniye i termicheskaya obrabotka metallov = Metal Science and Heat Treatment metals, 2017, no. 10 (748), pp. 35–40.

5. Safronov I. S. Zakonomernosti formirovaniya mekhanicheskikh svoystv amorfnonanokristallicheskikh metallicheskikh splavov, obrabotannykh lazernymi impul'sami nanosekundnoy dlitel'nosti [Regularities of the formation of mechanical properties of amorphousnanocrystalline metal alloys treated with laser pulses of nanosecond duration]. Saratov, IPR Media Publ., 2019. 144 p.

6. Ushakov I. V., Simonov Yu. V. Formation of surface properties of VT18u titanium alloy by laser pulse treatment. Materials Today: Proceedings, 2019, vol. 19 (5), pp. 2051– 2055. https://doi.org/10.1016/j.matpr.2019.07.072.

7. Simonov Yu. V., Ushakov I. V. Mekhanicheskiye svoystva poverkhnostnykh struktur titanovogo splava VT9 posle mnogokratnoy lokal'noy obrabotki nanosekundnymi lazernymi impul'sami [Mechanical properties of surface structures of titanium alloy VT9 after repeated local processing with nanosecond laser pulses]. Vestnik Moskovskogo gosudarstvennogo oblastnogo universiteta. Seriya: Fizika-Matematika = Bulletin of Moscow Region State University. Series: Physics-Mathematics. 2020, no. 2, pp. 19–35. https://doi.org/10.18384/23107251-2020-2-19-35.

8. Deng J., Chen C., Zhang W., Li Y., Li R., Zhou K. Densification, microstructure, and mechanical properties of additively manufactured 2124 Al–Cu Alloy by selective laser melting. Materials, 2020, vol. 13(19), pp. 4423. https://doi.org/10.3390/ma13194423.

9. Spierings A. B., Dawson K., Heeling T., Uggowitzer P. J., Schaublin R., Palm F., Wegener K. Microstructural features of Sc- and Zr-modified Al-Mg alloys processed by selective laser melting. Materials and Design, 2017, vol. 115, pp. 52–63. https://doi.org/10.1016/j.matdes.2016.11.040.

10. Li R., Chen H., Zhu H., Wang M., Chen C., Yuan T. Effect of aging treatment on the microstructure and mechanical properties of Al-3.02Mg-0.2Sc-0.1Zr alloy printed by selective laser melting. Materials and Design, 2019, vol. 168, рр. 107668. https://doi.org/10.1016/j.matdes. 2019.107668.

11. Popovich A. A., Sufiyarov V. Sh., Polozov I. A., Grigoriev A. V. Selektivnoye lazernoye plavleniye intermetallidnogo titanovogo splava [Selective laser melting of intermetallic titanium alloy]. Izvestiya vuzov. Poroshkovaya metallurgiya i funktsional'nyye pokrytiya = Proceedings of Higher Educational Institutions. Powder Metallurgy and Functional Coatings, 2018, no. 1, pp. 26–35. https://doi.org/10.17073/1997-308X-2018-1-26-35.

12. Wang W., Xu X., Ma R., Xu G., Liu W. and Xing F. The influence of heat treatment temperature on microstructures and mechanical properties of titanium alloy fabricated by laser melting deposition. Materials, 2020, vol. 13 (18), pp. 4087. https://doi.org/10.3390/ma13184087.

13. Li W., Zhou Z. Research on ultrasonic array testing methods of laser additivemanufacturing titanium alloy. Journal of Mechanical Engineering, 2020, vol. 56(8), pp. 141– 147. https://doi.org/10.3901/JME.2020.08.141.

14. Shulov V. A., Steshenko I. G., Teryaev D. A., Perlovich Yu. A., Isaenkova M. G., Fesenko V. A. Formation of residual stresses in the surface layers of titanium alloy targets irradiated with high-current pulsed electron beams. Inorganic Materials: Applied Research, 2019, vol. 10(3), pp. 529–531. https://doi.org/10.1134/S2075113319030407.

15. Shulov V. A., Gromov A. N., Teryaev D. A., Perlovich Yu. A., Isaenkova M. G., Fesenko V. A. Texture formation in the surface layer of VT6 alloy targets irradiated by intense pulsed electron beams. Inorganic Materials: Applied Research, 2017, vol. 8(3), pp. 387–391. https://doi.org/10.1134/S2075113317030212.

16. Glezer A. M., Shurygina N. A. Amorfno-nanokristallicheskiye splavy [Amorphnonanocrystalline alloys]. Moscow, Fizmatlit Publ., 2013. 452 p.

17. Guozhong Ts., Wang I. Nanostruktury I nanomaterialy. Sintez, svoystva i primeneniye [Nanostructures and nanomaterials. Synthesis, properties and application]. Moscow, Nauchnyi mir Publ., 2012. 515 p.

18. Abrosimova G. E. Evolyutsiya struktury amorfnykh splavov [Evolution of the structure of amorphous alloys]. Uspekhi fizicheskikh nauk = Physics-Uspekhi (Advances in Physical Sciences), 2011, vol. 181, no. 12, pp. 1265–1281. https://doi.org/10.3367/UFNr.0181.201112b.1265.

19. Sundar R., Ganesh P., Gupta R. K., Ragvendra G., Pant B. K., Vivekanand K., Ranganathan K., Rakesh K., Bindra K. S. Laser shock peening and its applications: a review. Lasers in Manufacturing and Materials Processing, 2019, vol. 6, pp. 424–463. https://doi.org/10.1007/s40516-019-00098-8.

20. Antony K., Clint T. C., Rakeshnath T. R. Study of porosity and build rate of the selective laser melting (SLM) of titanium and its statistical modelling for optimization. Lasers in Engineering, 2020, vol. 47(1-3), pp. 95–111.

21. Khairallah S. A., Anderson A. T., Rubenchik A., King W. E. Laser powder-bed fusion additive manufacturing: Physics of complex melt flow and formation mechanisms of pores, spatter, and denudation zones. Acta Materialia, 2016, vol. 108(16), pp. 36–45. http://dx.doi.org/10.1016/j.actamat.2016.02.014.

22. Ankudinov V. E., Aflyatunova D. D., Krivilev M. D., Gordeev G. A. Komp'yuternoye modelirovaniye protsessov perenosa i deformatsiy v sploshnykh sredakh [Computer modeling of transfer and deformation processes in continuous media]. Izhevsk, Udmurtsk Univ. Publ., 2014. 108 p.

23. Purin M., Zakharevich A., Gutareva N. Mathematical modeling of melting during laser heating of metal plate. MATEC Web of Conferences, 2017, vol. 110, pp. 01070. https://doi.org/10.1051/matecconf/201711001070.

24. Sharapov A. I., ChernykhA. A., Yartsev A. G., Peshkova A. V. Rasprostraneniye teplovogo potoka cherez materialy s sharovoy polost'yu [Distribution of heat flow through materials with a spherical cavity]. Izvestiya Yugo-Zapadnogo gosudarstvennogo universiteta. Seriya: Tekhnika i tekhnologii = Proceedings of the Southwest State University. Series: Engineering and Technology. 2019, vol. 9, no. 1 (30), pp. 49‒55.