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669.295:661.882

EFFECT OF ANNEALING ON THE STRUCTURAL AND TEXTURAL STATE AND PROPERTIES OF HOT-PRESSED TUBE FROM TITANIUM ALLOY PT-1M A. G. Illarionov,1, 2 F. V. Vodolazskii,1 M. S. Karabanalov,1 N. A. Barannikova,1, 3 and Ya. I. Kosmatskii4 Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 23 – 28, July, 2020.

The methods of orientation microscopy, x-ray diffraction phase analysis and microindentation are used to study the effect of annealing at 680°C on the structure, texture, and physical and mechanical properties of a hot-pressed tube from titanium a-alloy PT-1M. It is shown that annealing of the hot-pressed tube from alloy PT-1M in the a-range causes secondary crystallization and grain growth, which are accompanied by lowering of the hardness over cross section of the annealed tube from its external surface to the internal one. Annealing also produces reorientation of the main texture tangential prism components formed under the hot pressing. The presence of such texture components in the hot-pressed and annealed tube results in anisotropy of the hardness and of the elastic modulus in longitudinal and transverse sections of the tube.

Key words: titanium alloy PT-1M, tube billet, structure, texture, physical and mechanical properties.

later works, we determined the temperature and force parameters for making hot-pressed pipes [10]. An intermediate or a final heat treatment for titanium alloys is annealing in an air atmosphere or in vacuum [7, 11, 12]. Final annealing in vacuum provides a safe level of hydrogen content in the tube [11], and intermediate annealing in an air atmosphere yields a homogeneous surface oxide layer and a ductility margin [13] required for subsequent cold rolling. However, the reported data on the effect of annealing on the structure and properties of hot-pressed tubes from alloy PT-1M are quite scarce. For this reason, we devoted the present work to studying the structure and texture condition and the combination of properties after air annealing of a hot-pressed tube from alloy PT-1M.

INTRODUCTION Alloy PT-1M is a variant of commercial titanium based on an a-solid solution alloyed with some aluminum (within 0.2 – 0.7%) [1]. It has been developed at the Central Research Institute of Structural Materials “Prometey” Named by I. V. Gorynin (TsNII KM “Prometey”) [2, 3] and is chiefly used for making cold- and hot-deformed weldable semiproducts [4], in particular, special-size tubes [5, 6] for ship water-supply systems with operating temperature up to 150°C [2]. In some cases, tubes from titanium alloys including PT-1M are manufactured by hot pressing of tubular billets [7]. We have shown in [8] that a large-size tubular billet from alloy PT-1M may have an inhomogeneous macro- and microstructure with largest grains in the center of the cross section of the semiproduct; during the subsequent expansion at 850°C the structure is refined and becomes more homogeneous due to occurrence of primary recrystallization [9]. In 1

2 3 4

METHODS OF STUDY We studied templat