E. A. Budovskikh

Surface layer of commercially pure VT1-0 titanium after electric-explosion alloying and subsequent treatment by a high-intensity pulsed electron beam

The structure, phase composition, and mechanical, tribological, and corrosional properties of commercially pure VT1-0 titanium are investigated after electric-explosion alloying and subsequent treatment by a high-intensity pulsed electron beam. Treatment conditions that greatly increase the properties of the titanium are identified. The physical factors at work here are considered.

Formation of dislocation-free nanostructures in metals on electroexplosive alloying

820 Dramatic improvements in functional materials are possible by means of nanostructures [1, 2]. Funda mental research into nanostructures over the past twenty years has resulted in significant modification of the traditional dislocational explanation of strength and plasticity [3]. Definite progress has already been made in terms of pure metals [4]. Considerable research is still required for multiphase composites [5].

Combined electron-ion-plasma doping of a titanium surface with yttrium: Analyzing structure and properties

A titanium surface layer is modified with yttrium by combining electroexplosive doping and high-intensity electron-beam irradiation. The element and phase content, defect substructure, and mechanical and tribological characteristics are investigated for the doped layer. Saturating the surface titanium layer with yttrium, oxygen, and carbon atoms is shown to produce a metalloceramic layer reinforced with oxides and titanium and yttrium carbides that results in a multifold increase in microhardness and reduces the friction coefficient and wear rate in the modified layer.

MAX phases in titanium and aluminum alloys

The crystalline structures in the Ti-Al-C and Ti-Si-C systems are analyzed, and experiments are conducted with VT6 titanium alloy and eutectoidal Silumin (Al-12% Si) subjected to electroexplosive alloying and electron-beam treatment. Diffraction analysis reveals the formation of MAX phases (Ti3SiC2 and Ti3AlC) in the modified layer of these alloys.

Carbidization of Titanium Alloys in Electroexplosive Carburization and Additional Heat Treatment

When pulsed multiphase plasma jets formed in the electrical explosion of wire act on the surface of metals and alloys, the resulting structure is characterized by improved performance—for example, higher wear resistance and high-temperature strength [1]. In the carburization of titanium by the explosion of graphite fiber, alloying with the plasma components of the jet is accompanied by alloying with condensed explosionproduct particles, as shown in [2]. Titanium alloys tend to bind with the frictional pair and hence their wear resistance is low. Therefore, electroexplosive alloying may be used for surface hardening of titanium-alloy components that operate in the presence of wear. To improve the wear resistance, reduce adhesion, and reduce the frictional coefficient of titanium alloys, only nitriding has been used on an industrial scale. As yet, there are no practically acceptable methods of carbidization [3]. However, most structure-free carbon (graphite) at the surface of the titanium alloy after electroexplosive carburization may be subjected to additional heat treatment so as to produce hard, wear-resistant, and heatproof titanium-carbide phase at the alloy surface. In the present work, we study the possibility of additional heat treatment of VT1-0 and VT20 alloys. Technically pure VT1-0 alloy has an α structure in the annealed state. VT20 alloy (composition Ti‐Al‐Zr‐ Mo‐V) is an industrial pseudo- α alloy and is widely used for the manufacture of high-temperature components.

Morphological features of the crystallization of surface iron and nickel layers in electroexplosive alloying

The nanostructure of surface layers formed in electroexplosive alloying has recently been demonstrated. The corresponding structure is revealed as a result of layer-by-layer study of zones of electroexplosive alloying—carburization and carboboriding of nickel [1] and iron [2, 3]; boriding [4], copper plating, and cuproboriding [5] of nickel; and copper plating and cuproboriding [6], aluminum plating [7], and alumoboriding [8] of iron—by highly informative diffractional electronmicroscope analysis of thin foil. The results provide the basis for electroexplosive alloying to produce nanocomposite layers on the surface and permit the selection of means of controlling the structure formation of the modified layers. It is found that several layers with different structural and phase states alternate in an orderly fashion over the depth of the electroexplosive-alloying zone. The volume ratio between the layers is different in different types of alloying. The basic layers are characterized by cellular crystallization and a granular structure. Usually, the change in morphology of the crystallization front is described on the basis of the theory of concentrational supercooling [9]. Accordingly, these concepts are used in the present work to analyze the crystallization of practically important systems formed at the surface of iron and nickel by electroexplosive treatment. Plates of technically pure 0.08ZhR iron (thickness 3‐5 mm) and NP1 nickel (thickness 2 mm) are treated at the pressure of the residual atmosphere in a technological chamber (100 Pa). The explosive wires are graphite fiber [1‐3] and nickel [4], aluminum [7, 8], and copper [5, 6] foil of mass 180, 220, 40, and 100 mg, respectively. In boriding nickel and two-component alloying in the explosive region, a weighed portion of amorphous-boron powder (60 mg) is introduced. The effective treatment time is 100 µ s; the absorbed power density at the jet axis is 6.0 GW/m 2 ; the pressure in the impact-compressed layer formed close to the irradiated surface is 14.2 MPa. Foil for electron-microscopic investigation is prepared by electrolytic thinning of plates cut by electrospark erosion parallel to the treated surface. Jet treatment is used for one-sided polishing of the foil. Surface treatment in electroexplosive alloying is by pulsed heterogeneous plasma jets formed in the discharge of a capacitive energy store at a wire, using a coaxial system of current-bearing electrodes. The jets contain a purely plasma high-speed head, with gradual increase in the content of condensed explosion-product particles and powder toward the tail. As a result of thermalization of the plasma on impact at the surface, the metal is heated and, with certain parameter values, melts. The condensed particles in the tail of the jet interact with the melt and form the surface relief. In very intense treatment, as in the present work, the surface relief is also formed on account of radial melt flow under the jet pressure at the surface, from the center to the periphery of the treatment zone. Preliminary optical-microscope study of chemically etched transverse sections shows that central, intermediate, and peripheral regions may be distinguished over the radius of the treatment zone; they differ in the roughness of the external surface and in the depth and degree of alloying. These parameters are greatest in the central region (diameter 20 mm) under the nozzle of the plasma accelerator. On the basis of these results, subsequent structural and phase analysis is based on transmission electron-diffraction microscopy of thin foil in the intermediate region of the alloying zone, at a distance of 10‐15 mm from the center, where its thickness is 20‐25 µ m. The surface of the samples is investigated, as well as layers at different depths. The volume fraction of a particular phase is calculated from the area that it occupies in comparison with the total area of the microphotograph.

Electroexplosive Boron-Aluminum Coating of Iron: Phase Composition and Defect Substructure

One method of surface alloying is to treat metals and alloys with heterogeneous plasma jets consisting of the electric-explosion products of wire. Expanding the scope and applicability of the method, a weighed portion of powder to be transferred to the surface by the plasma jet may be placed in the region where the explosion is to occur. This permits two-component electroexplosive alloying [1, 2]. In the present work, continuing such research, we consider the formation of the phase composition and defect substructure of the surface of pure iron in electroexplosive boron‐aluminum coating. In selecting the type of electroexplosive alloying,