Materials science

Prediction of the strength properties of bars from alloy VT6 with globular-lamellar structure

Yu.B. Egorova, S.V. Skvortsova, L.V. Davidenko, O.N. Gvozdeva, S.B. Belova

It has been established that at the same strength level, the relative elongation and reduction of area of rolled bars of the VT6 alloy with a globular-lamellar structure, occupy an intermediate position between the properties of specimens with globular and lamellar structures. Experimental data are presented on the combined effect of the chemical composition and parameters of the globular-lamellar structure on the mechanical properties of rolled bars from the VT6 alloy. Relationships for predicting the ultimate strength depending on the structural equivalents for aluminum, molybdenum, parameters of the globular-lamellar structure and Rockwell hardness are statistically substantiated.

Keywords: titanium alloy VT6, rolled bars, chemical composition, structure, mechanical properties, statistical studies.

Influence of the structure and superelastic properties of titanium nickelide on the choice of the volume fraction of the reinforcing filler in the «Polyethylene – NiTi» composite

D.E. Gusev, D.V. Burdin

The influence of the chemical composition and structure on the characteristics of the superelastic behavior of the NiTi-alloys wire, which is used as reinforcing filler in a composite material with a polyethylene matrix, is shown. A method for evaluating the performance of wire reinforcing elements made of titanium nickelide during their deformation by bending is proposed. A method is proposed for calculating the optimal volume fraction of the filler, which ensures high superelastic properties of the composite.

Keywords: NiTi alloy, composite, polyethylene, superelastic.

Influence of thermobaric, concentration and kinetic parameters of hydrogen-rich annealing during thermal hydrogen treatment on the phase composition and structure of a titanium alloy with a high aluminum content

A.A. Lidzhiev, A.V. Ovchinnikov, E.O. Agarkova, A.M. Mamonov, A.V. Neiman, Yu.N. Kusakina

The influence of the parameters of hydrogen-rich annealing by the Sieverts method during thermal hydrogen treatment of the Ti-8.7Al-2.0Mo-1.5Zr alloy on its structure and phase composition has been studied. It has been established that an increase in the initial pressure of hydrogen gas over the alloy from 100 to 130 kPa at a temperature of 850°C leads to the formation of structures that are inhomogeneous in cross section with a predominance of a lamellar α-phase in the surface layer and a small-globular recrystallized α-phase in the core. It is shown that the presence and completeness of the eutectoid decomposition of the hydrogen-containing β-phase upon cooling depend on the concentration of introduced hydrogen and the cooling rate on the temperature of hydrogen-rich annealing.

Keywords: titanium alloy, hydrogen, hydrogen pressure, structure, eutectoid transformation.

Manufacturing technologies

Special aspects of ship screw propellers manufacturing from titanium alloys

M.N. Saubanov, L.G. Krouglov

The patent research and literary studies about the technology and development of chill tooling for the large castings manufacture by the chill casting method has been carried out. The optimal design of the chill tooling has been developed; the thermal balance is calculated taking into account the heat exchange between the casting and the mold. An expanding pouring gate system is used to ensure smooth flow of the melt into the operating section of the mold cavity and directional solidification of the casting. The developed design and technology provides increased durability, an increase in the service life of the chill, reduces its warping, improves the quality of castings of screw propeller blades and reduces the cost of titanium castings.

Keywords: metal chill casting tooling, ship screw propellers blades, thermal balance, calorimetric temperature of the system, vacuum melting furnace, chill connector, arc melting of titanium alloy.

Processing technologies

Improving the quality of stamped forgings of the VT20 titanium alloy disc type

P.A. Golovkin

By comparing the results of metallographic analysis of the forgings material and mathematical modelling of the process of their forming, a method of improving the quality of stamped forgings of disc type made of titanium alloy VT20. By reducing the heating temperature and changing the shape of the billets, as well as refining the working profile of the die, the non-uniformity of deformation processes was reduced and a more homogeneous structure of their material was obtained.

Keywords: disc-type part, hot forging, titanium alloy, deformation, temperature, structure, mathematical modelling.

Application. Quality. Market

Obtaining gradient oxide anode films on titanium alloys by immersion with increased voltage

A.E. Avramenko, A.E. Dryukova

The article discusses the application of an oxide gradient film to titanium alloys by the immersion method, in which the product is gradually removed from the electrolyte with a parallel increase in the voltage value. The method allows you to obtain gradients with color transitions caused by an increase in voltage. This method, if there are more than two transitions in the gradient, forms a defective area (sometimes a color omission or its translucency), for which a mathematical dependence has been established. It consists in the relationship between the voltage difference between the final and initial values of the gradient anodizing voltage (U -Tip - U-Tip) and the stress region of the defective color (U-D2 -U-D1) and is expressed by a coefficient k equal to [1;1,3]. The method can be used to create a gradient with a color skip, as well as a gradient without a skip, which allows you to get smooth transitions and bright colors at voltages from 51V.

Keywords: titanium, gradient films, anodizing, color skipping, immersion method.

Modern aspects of the use of titanium alloys as materials for the manufacture of armor elements (review)

Y.N. Kusakina, L.V. Fedorova, A.P. Neiman

The paper considers the actual possibilities of using titanium alloys as materials for creating structures and armor elements. Tendencies have been noted for the creation of new alloys, for example, VST 2 (VST-2B), with a cost lower than the existing serial alloys VT23, VT6 and OT4-1, traditionally used in the aircraft industry and other industries. The possibilities of creating new compositions of alloys for armor barriers, for example, VT-Bn, are also shown. The ongoing studies of serial titanium alloys, for example, VT6 and VT23, are noted in order to create gradient structures by thermal hydrogen treatment that ensure the survivability of armor barriers. In addition, titanium alloys have found application in the composition of composite armor barriers, an example is a heterogeneous monolithic ceramic-metal composite material based on pseudo-β titanium alloy VST 2 with a plasma-treated surface. Also described are the use of alloy OT4 for the creation of discretely reinforced armor elements and a multilayer material of the "Sandwich" type based on (a+b)-titanium alloy VT6 and pseudo-β titanium alloy VT35.

Keywords: titanium alloys, armor structures and elements, armor materials, sparingly alloyed titanium alloy, ceramic-metal composite material.