Alexey Goncharov

A thin-walled product made of AZ31 magnesium alloy was successfully fabricated using wire-feed electron-beam additive manufacturing. The microstructure of the initial wire, used as a precursor, comprises a α-Mg(Al, Zn) solid solution and a minor amount of the Al₈Mn₅ intermetallic phase. The microstructure of the as-printed AZ31 alloy exhibits a three-phase structure: α-Mg(Al, Zn), Al₈Mn₅, and β-Mg₁₇Al₁₂. It was proposed that the secondary β-phase was formed via a primary solidification process upon the cooling of the welded layers. The texture effect was evident in the direction, corresponding to the printing direction, while other crystallographic orientations demonstrated near-equal pole densities as the XRD lines. The yield strength for the as-printed alloy was found to be 86 MPa; the tensile strength reached 240 MPa; and the relative elongation was 21.5%. For the first time, the corrosion resistance of an EBAM-fabricated AZ31 alloy was studied. It was revealed that the corrosion current density in the referenced as-cast and as-printed alloys was below 2·10⁻⁴ A/cm².

The article considers the development of a setup for studying the thermo-EMF of metallic materials from industrially produced alloys for various purposes.

The relevance of creating specialized computer programs that convert a virtual 3D model of an object into machine code (G-code) for controlling the process of 3D printing products from wire raw materials is substantiated. It is shown that for wire-based additive technologies, a fundamentally important requirement is to ensure the continuity of the surfacing trajectory within one section. A method for determining a continuous surfacing trajectory is proposed, the implementation of which requires two stages: performing a numerical analysis of a two-dimensional region with boundary conditions describing this section; and running a heuristic algorithm for the movement of the surfacing head, in which the direction of movement is selected based on the results of the analysis. The procedure for setting boundary conditions and an algorithm for numerically solving the boundary value problem of determining the field of the “height” function for each section are described. The principles of operation of the heuristic algorithm for selecting the direction of head movement based on the calculated height field and continuous determination of the proximity of adjacent layers and section boundaries are disclosed. An analysis of the algorithm operation is carried out using a section with holes as an example, and the potential of using numerical methods to calculate the change in the temperature field during the surfacing process is shown.

A computer model has been developed to investigate the processes of heat and mass transfer under the influence of concentrated energy sources on materials with specified thermophysical characteristics, including temperature-dependent ones. The model is based on the application of the volume of fluid (VOF) method and finite-difference approximation of the Navier–Stokes differential equations formulated for a viscous incompressible medium. The “predictor-corrector” method has been used for the coordinated determination of the pressure field which corresponds to the continuity condition and the velocity field. The modeling technique of the free liquid surface and boundary conditions has been described. The method of calculating surface tension forces and vapor recoil pressure has been presented. The algorithm structure is given, the individual modules of which are currently implemented in the Microsoft Visual Studio environment. The model can be applied for studying the metal transfer during the deposition processes, including the processes with electron beam spatial oscillation. The model was validated by comparing the results of computational experiments and images obtained by a high-speed camera.

Investigation of relation between parameters of weld penetration shape and energy efficiency of electron beam welding process was performed in the paper. Analysis of welds cross sections of 316 L(N) steel weld joints obtained by the electron beam welding in the wide range of welding regimes is carried out. It is shown that the dependences of the thermal efficiency on the penetration area at different welding speeds are linear. According to the results, the thermal efficiency coefficient may exceed the ultimate theoretical value for linear heat source. Beam sweep does not affect essentially on the rate of thermal efficiency coefficient, since sweep application leads to an insignificant change in the area of the boundary of the weld pool with the base metal, and therefore, the amount of energy removed through this boundary also changes insignificantly and the penetration area remains almost constant.

The results of studies of magnetic and thermoelectric properties of pearlite, martensitic and austenitic steels are given. The magnetization curves for the materials under study, as well as dependences of absolute thermoelectric power on the material temperature are obtained. The data of magnetic induction changing at the control points above the welded samples during EBW are achieved. The simulation of the magnetic field distribution during electron beam welding of dissimilar steels under the conditions of the thermopower currents generation is carried out. The shape of the electron beam being deflected in the magnetic field of thermoelectric currents is calculated. The calculated values are compared to the experimental results.

The paper is devoted to identifying features of structural non-homogeneities formation in dissimilar welded joints of carbon steel 20 to corrosion-resistant austenitic 12Kh18N10T steel, obtained by tungsten inert gas welding (TIG), as well as studying of their influence on the mechanical characteristics of welded joints under static and cyclic loading. Differences in the formation of a diffusion carbide interlayer in weld metal alloyed with nickel and manganese are established. When austenite is alloyed with nickel, bulk carbon diffusion occurs, while in manganese austenite boundary diffusion becomes the main mechanism for carbon diffusion, which occurs mainly along grain and sub-grain boundaries of austenite. As a result of mechanical tests, it was established that under static tension welded joint works under conditions of strengthening by a soft (ferritic) layer due to the restraint of transverse deformations by more solid (carbide) layer. The limits of soft interlayer dimensions, under which the softening of welded joint does not occur, are established that will allow to proceed to the extreme temperature-time parameters of heat treatment and operation of welded joint.