Features of the welded seam material crystalliza-tion in Ti-TiB alloy under electron-beam welding conditions





titanium alloys, titanium boride, micro-structure, mechanical properties, welded joint, electron-beam welding, heat treatment


Natural metal composite materials represent a promising class of modern structural materials that need to be welded. Such materials can be welded by fusion, as has been established with the Ti-TiB alloy as an example. The enhanced operational properties of such materials are determined by the microstructure, which is characterized by the presence of microfibers of borides, carbides, or silicides in the metal matrix. To preserve the mechanical properties of materials in a welded joint, it is necessary to ensure the formation of reinforcing microfibers in the welded seam material. Determination of formation mechanism of boride microfibers, originated in the welded seam material, will become the basis for optimizing of fusion welding modes, in particular, electron beam welding mode.

The purpose of this study is the determination of formation mechanism of boride microfibers originated in the welded seam material. Two most probable variants of the formation mechanism are analyzed, which involve eutectic decomposition during crystallization from a liquid melt or eutectoid decomposition from a metastable crystallized alloy. The third version is a mixed variant of the two above-mentioned mechanisms.

In the article the results of metallographic analysis of features of boride phase distribution and an analysis of elemental composition of boride fibers based on local Auger electron spectroscopy are presented. The object of study was a Ti-TiB alloy joint obtained by electron-beam welding. The analysis factors were the features of size, orientation, and nature of the distribution of boride phase microfibers in different areas of the welded seam. The characteristic elemental composition of boride microfibers, which characterizes the correspondence to equilibrium phases, is also studied.

The degree of deviation of the ratio of boron and titanium in such a phase from the thermodynamically equilibrium in different layers of the material of the welded seam, formed by an electron beam in vacuum, is determined. The dependence of boride phase distribution under various conditions of heat exchange in the welded seam material on the side surfaces and in the central regions is established. It is shown that some of boride microfibers formed in the material of the welded seam are characterized by a deviation from the thermodynamically stable composition ТіВn (n = 1) to ТіВn (n = 0.85). The dendritic nature of boride microfibers distribution and the presence of meta-stable phase formations on Ti and B basis provide the grounds for proposing the predominant mechanism for the formation of structure of the welded seam material in the Ti-TiB alloy during crystallization.

An analysis of hypothetical variants of the formation mechanism of boride microfibers originated in the welded seam material showed that the formation of a dendritic type of structure is characteristic for the growth of crystals of a new phase in the liquid phase. Such growth is characterized by the formation of equilibrium phases. The presence of a significant amount of non-equilibrium boride phase in the welded seam indicates the residue of non-equilibrium boron in the titanium matrix and continuation of growing of boride fibers in the crystallized welded seam. A determined mechanism for formation of boride microfibers originated in the welded seam material is eutectic decomposition during crystallization from a liquid melt with the formation of TiB microfibers and further growth of such crystals due to eutectoid decomposition from a metastable crystallized Ti-TiB alloy. The results obtained make it possible to understand the mechanism of formation of a welded seam in welded natural-composite metal materials, which permits to develop the recommendations for optimizing the welding technology for such materials.


  1. V.N. Alehnovich et al., Electron-beam processing of materials, Belorusskaja nauka: Minsk, Belarus, 2006.
  2. S.V. Akhonin et al., “Properties of high-strength titanium alloy T110 joints made by fusion welding”, Autom. Weld., No. 1, pp. 54–57, 2014. Available: https://patonpublishinghouse.com/as/pdf/2014/as201401all.pdf
  3. G.M. Grigorenko et al., “Structure and properties of titanium alloy, alloyed with boron, produced by the method of electron beam remelting”, Electrometall. Today, No. 1(122), pp. 21–25, 2016. DOI: https://doi.org/10.15407/sem2016.01.03
  4. Ju.N. Taran and V.I. Mazur, Structure of eutectic alloys, Metallurgija: Moscow, Russia; 1978.
  5. P. Loboda et al., “Production and Properties of Electron-Beam-Welded Joints on Ti-TiB Titanium Alloys”, Metals, No. 10, pp. 522, 2020. DOI: https://doi.org/10.3390/met10040522
  6. I.S. Miroshnichenko, Quenching from a Liquid State, Metallurgija: Moscow, Russia, 1982.
  7. B. Chalmers, Principles of Solidification, Wiley: New York, NY, 1964.
  8. M.A. Tikhonovsky, “Investigation of directional phase transformation and development of microcomposite materials in NSC KIPT”, Problems of Atomic Science and Technology, Vacuum, Pure Materials, Superconductors, No. 6, Vol. 14, pp. 115–127, 2004. Available: https://vant.kipt.kharkov.ua/ARTICLE/VANT_2004_6/article_2004_6_115.pdf
  9. S.V. Ivanova et al., “Directional crystallization of Co-Si alloys of non-eutectic composition”, Izvestiya Vuzov. Tsvetnaya Metal-lurgiya, No. 3, pp. 122–126, 1975.
  10. A.I. Somov, V.Ja. Sverdlov and M.A. Tikhonovsky, “Influence of the rate of crystallization and heat treatment on the structure and properties of the eutectic composition Cu-CuxZr”, Physics and Chemistry of Materials Treatment, No. 4, pp. 124–129, 1978.
  11. A.I. Somov et al., “Influence of the composition and crystallization conditions on the microstructure and strength of the Ni–NbC eutectic composition”, Physics of Metals and Metallography, No. 48, Vol. 2, pp. 318–322, 1979. Available: http://impo.imp.uran.ru/fmm/Electron/vol48_2/abstract13.pdf
  12. A.I. Somov and M.A. Tikhonovsky, “Eutectoid compositions”, Metallovedenie i termicheskaya obrabotka metallov, No. 11, pp. 130–131, 1976.
  13. A.I. Somov et al., “Microstructure defects and dispersion of an oriented eutectoid in cobalt-silicon alloys”, Physics of Metals and Metallography, No. 38, Vol. 2, pp. 343-348, 1974. Available: http://impo.imp.uran.ru/fmm/Electron/vol38_2/abstract17.pdf




How to Cite

. P. Loboda, “Features of the welded seam material crystalliza-tion in Ti-TiB alloy under electron-beam welding conditions”, Mech. Adv. Technol., vol. 7, no. 1 (97), pp. 36–42, Apr. 2023.



Up-to-date machines and the technologies of mechanical engineering