2020 №09 (03) DOI of Article
2020 №09 (05)

Automatic Welding 2020 #09
Avtomaticheskaya Svarka (Automatic Welding), #9, 2020, pp. 36-41

Influence of local heat treatment on mechanical characteristics of welded joints of intermetallic tial system obtained by electron beam welding

L.M. Lobanov, E.A. Asnis, N.V. Piskun, E.L. Vrzhyzhevskyi, L.M. Radchenko
E.O. Paton Electric Welding Institute of the NAS of Ukraine. 11 Kazymyr Malevych Str., 03150, Kyiv, Ukraine. E-mail: office@paton.kiev.ua

Welded joints of intermetallic β-stabilized alloy of TiAl system – Ti–44Al–5Nb–3Cr–1.5Zr (at. %) were investigated. Intermetallic blanks of 3 and 10 mm thickness were welded by electron beam welding. In order to prevent the occurrence of cold cracks in the welded joints of titanium aluminide samples of different thickness, the following post-welding local heat treatment using an electron beam was performed. This method of processing is one of the most attractive for improving the structure of the ingot and reducing the level of residual welding stresses, which, in its turn, significantly increases the mechanical properties of the alloy. Static tensile tests were performed to assess the strength of welded joints. The samples failed in the base material. The paper presents histograms showing the values of tensile strength (σt) of welded joints obtained during tensile test for samples of different thickness with and without LHT application. It is shown that the use of local heat treatment increases the tensile strength of samples of 3 and 10 mm thickness by 1.8 times, compared with samples produced without LHT. In addition, the values of this characteristic for welded joints of different thicknesses, which are obtained using this technique, are quite uniform. Comparative analysis of the results of tensile tests and the results of microhardness studies was performed, which showed that destruction of the samples took place in the zone of lowering of mechanical properties. The nature of fractures of different parts of the welded joint was studied, which confirmed that fracture occurs in the zone of brittle part of the sample. It is known that mechanical properties of the welded joint are closely related to its structural state. During local heat treatment, an additional β0 (B2) phase appears in the structure, which increases the ductility of the weld material. 14 Ref., 2 Tabl, 9 Fig.
Keywords: intermetallic alloy of TiAl system, electron beam welding, local heat treatment, mechanical tensile tests, tensile strength, structural state, microhardness

Received: 29.07.2020


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