Fracture surface analysis of a quenched (α+β)-metastable titanium alloy

Fracture surface analysis is conducted by means of SEM for VT16 titanium alloy specimens solution-treated at temperatures ranging from 700 to 875 °C, water-quenched and subjected to tensile testing. A cup and cone shape failure and dimple microstructure of the fracture surface indicates the ductile behavior of the alloy. Dimple dimensions correlated with the β-grain size of the alloy in quenched condition. The fracture area (namely, the size; the cup and cone shape) depends on the volume fraction of the primary α-phase in the quenched sample. However, the fracture surface changes considerably when the strain-induced β-α''-transformation takes place during tensile testing, resulting in the increase of alloy ductility. © 2017 Author(s).Russian Foundation for Basic Research, RFBR: 15-08-08299 АCouncil on grants of the President of the Russian Federation: MK-6311.2016.8The work was supported by the grant of the President of Russian Federation, No. MK-6311.2016.8, and RFBR grant No. 15-08-08299 А

The Influence of Molybdenum Equivalent on the Anisotropy of Thermal Expansion of Titanium Martensite Lattice

The structure of the martensite formed by quenching in titanium alloys, as well as the connection between the rhombic lattice α - martensite and anisotropy of thermal expansion was investigated. Τhe methods of the X-ray and thermal XRD phase analyzes have been used to study the relationship between martensite crystal lattice, the coefficient of thermal expansion (CTE) and molybdenum and aluminum equivalent.     Keywords: titanium alloys, martensite, CTE, XRD-analysi

Effect of the method for producing Cu-Cr3C2 bulk composites on the structure and properties

Copper-chromium carbide composites containing a carbide phase of 20-30 vol% were obtained with the use of solid- and liquid-phase mechanosyntheses, followed by magnetic pulse compaction (MPC) and spark plasma sintering. The morphology, structural-phase composition, density, hardness and electrical conductivity of the composites were investigated. The structure of composites obtained by MPC represents regions of copper matrix hardened by superfine carbide precipitates surrounded by a layer of chromium carbide. In the composites obtained by spark plasma sintering, the copper matrix hardened by superfine carbide precipitates was divided into areas surrounded by a copper-chromium layer. A composite obtained by the MPC of the powders synthesized using solid-phase mechanosynthesis (MS) (copper, chromium and graphite) had the highest values ofVickers microhardness (4.6GPa) and Rockwell hardness (HRA 69). The best value of electrical conductivity (36% IACS) was achieved using liquid-phase MS (copper, chromium and xylene) and spark plasma sintering. Liquid-phase MS is the only way to synthesize the powder with a small amount of the carbide phase and without contamination. © 2017 Indian Academy of Sciences.Government Council on Grants, Russian FederationFederal Agency for Scientific Organizations: 0428-2014-0002, 0389-2014-0002This work was supported by the Government of the Russian Federation (Federal Agency for Scientific Organizations) under the themes of the state task, no. 0389-2014-0002 and no. 0428-2014-0002 and by the Program of UD RAS, Project reg. no. AAAA-A17-117040610324-3

Parameters Evolution of Orthorhombic Martensite Lattice in VT16 Titanium Alloy During Heating

The material of the study was (α + β) -titanium alloy VT16. Samples were quenched from different temperatures and then they were heated in situ on X-ray diffractometer. It has been established that the period “b” of the orthorhombic martensite lattice showed negative values of the coefficient of thermal expansion during heating.     Keywords: titanium alloys, XRD-analysis, orthorhombic martensite, coefficient of thermal expansion

Effect of Thermomechanical Treatment Parameters on Structure, Phase Composition and Mechanical Properties of Ti-3Al-5Mo-4.5V Titanium Alloy

The structure, phase composition and mechanical properties of (α+β) - titanium alloy solution treated at 850 C, cold-rolled at the reduction ratio in the range of 0... 45%, followed by ageing at 450, 500, 550 C for 0.5, 1.5, 3 hours was studied using XRD, microindentation and tensile testing. The influence of strain level at cold rolling and time-temperature parameters of ageing on the formation of structure and phase composition of solution treated and water quenched Ti-3Al-5Mo-4.5V alloy was investigated and discussed in terms of tensile properties and microhardness. The parameters of low temperature thermomechanical treatment (LTMT) of the (α+β) - alloy were proposed to obtain a high-strength state. © Published under licence by IOP Publishing Ltd.This study was financially supported by the State Assignment, grant number 0836-2020-0020. The research equipment was purchased with the support from Act 211 of the Government of the Russian Federation, contract No. 02.A03.21.0006

Special features of the structure and phase composition of a Ti-23Al-26Nb/Al layered material obtained by plasma-spark sintering

Special features of formation of the structure of a layered intermetallic material based on titanium aluminide obtained by the method of plasma-spark sintering of foils are studied. The dependence of the structure on the temperature-and-time treatment parameters is determined. © 2013 Springer Science+Business Media New York

Способ термомеханической обработки прутков из двухфазных титановых сплавов для получения низких значений термического коэффициента линейного расширения в направлении оси прутка

Изобретение относится к области металлургии, а именно к способам термомеханической обработки прутков из двухфазных титановых сплавов. Способ термомеханической обработки прутков из двухфазных титановых сплавов с молибденовым эквивалентом от 3,3 до 22% включает закалку прутка и его холодную деформацию. Перед закалкой пруток подвергают горячей деформации при температуре в диапазоне от 500°C до Тпп-20°C с обеспечением аксиальной текстуры ?-фазы с полюсной плотностью не менее трех. Закалку прутка осуществляют с температур в диапазоне от 720°C до Тпп с последующей холодной деформацией вдоль оси прутка при температуре не выше 300°C и с относительным удлинением от 1 до 30%, где Тпп - температура полиморфного превращения сплава. Сплав характеризуется низким термическим коэффициентом линейного расширения при высоких значениях прочности и удовлетворительной пластичности. 1 ил., 2 табл., 1 пр

INFLUENCE OF HEAT TREATMENT REGIME ON STRUCTURE, PHASE COMPOSITION AND HARDNESS OF ALLOY Ti–21Al–23Nb–1V

The intermetallic alloy Ti–21Al–23Nb–1V after this heat treatment mode was investigated: heating 1060 oC, holding 20 minutes, cooling with furnace to 800 °C, holding 2 hours, heating 900 oC, holding 1 and quenching in water. It was found α2‑phase separation occurs along the boundaries when cooled to a temperature of 800 °C. Increasing the treatment temperature to 900 °C and holding at this temperature does not increase its quantity.В работе проведено исследование интерметаллидного сплава Ti–21Al–25Nb–1V после термообработки по следующим режимам: нагрев 1060 °C, выдержка 20 минут, охлаждение с печью до 800 °C, выдержка 2 часа, нагрев до 900 °C, выдержка 1 час и закалка в воду. Установлено, что выделение α2‑фазы происходит по границам при охлаждении до температуры 800 °C. Повышение температуры обработки до 900 °C и выдержка при данной температуре не приводит к увеличению ее количества.Работа выполнена в рамках гос.задания Минобрнауки РФ (№ 11.8386.2017/БЧ)