Electrometallurgy Today, 2021, №03



2021 №03 (07)

DOI of Article 10.37434/sem2021.03.08

2021 №03 (01)

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Electrometallurgy Today (Sovremennaya Elektrometallurgiya), 2021, #3, 49-57 pages

Тhe processes of structure formation during directional crystallization of heat-resistant intermetallic alloy of Tial system and their influence on increase of material plasticity

N.V. Piskun

E.O. Paton Electric Welding Institute of the NAS of Ukraine. 11 Kazymyr Malevych Str., Kyiv, 03150, Ukraine. E-mail: office@paton.kiev.ua

Abstract
The paper presents the results of studying the processes of structure formation in a heat-resistant intermetallic alloy of titanium-aluminium system at directional crystallization by the method of induction crucibleless zone melting and their influence on the mechanical properties. Advantages of directional crystallization of the intermetallic alloy by the method of crucibleless zone melting over other processing methods were determined. It is shown that application of this method allows obtaining the optimal structure and properties of the ingot without application of gasostatic isothermal pressing or multistep heat treatments. The principles and purposes of microalloying of TiAl system (Nb, Zr, Cr) and mechanism of the influence of each alloying element on the alloy properties have been analyzed. The processes of structure formation were studied and features were determined of phase transformations of Ti–44Al–5Nb–3Cr–1.5Zr alloy, taking place during induction crucibleless zone melting. It was proved that the developed technological process of induction crucibleless zone melting of β-stabilized intermetallic Ti–44Al–5Nb–3Cr–1.5Zr alloy ensures directional crystallization, refinement of the intermetallic grain size and allows controlling the ingot structure. The optimum phase balance, submicron interlamellar spacing and predominant orientation of the lamels along the temperature gradient are controlled by melting process parameters. Results of mechanical testing at room and high temperatures are given. These results are compared with the results of initial material testing and their compliance with the requirements for industrial application of such alloys in aircraft industry is demonstrated. It is shown that application of directional solidification at induction crucibleless zone melting promotes formation of a specific microstructure that has a positive effect both on plasticity and heat-resistance of the material, and leads to an essential increase of the modulus of elasticity. Ref. 15, Tabl. 3, Fig. 6.
Keywords: intermetallics; crucibleless zone melting; directional crystallization; structure; mechanical characteristics; modulus of elasticity; elongation

Received 01.07.2021

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