This paper examines the effect of scanning strategy (unidirectional scan, island scan and a scan with a 60о turn of the laser beam between layers) during selective laser melting and heat treatment on the crystallographic texture and mechanical properties of VZh159 alloy specimens. Application of different scanning strategies leads to two types of crystallographic texture formed in specimens: the axial component <100> gets reinforced in the unidirectional strategy, while it is the texture component {100}<001> in the other cases. After printing, the specimens were subjected to different regimes of heat treatment. They included quenching from 1,100 oC; quenching from 1,100 oC and ageing at 800 and 700 oC; quenching from 1,100 oC and ageing at 900, 800, 700 and 650 oC. When heat treatment (ageing) tests are conducted at room temperature, it leads to increased yield point and strength as a result of secondary phase precipitation at grain boundary and in grain core, while plasticity drops. During high temperature tests, no strength gain was found after heat treatment. In all heat treatment regimes, the authors observed anisotropy of mechanical properties in the specimens caused by the crystallographic texture that remains after heat treatment. The maximum strength and yield point were detected at 45о load application to growth direction during printing. At the same time, the anisotropy of yield point does not change during high temperature mechanical testing (at 850 oC) and has no dependence on the amount of additional precipitates. It suggests that crystallographic texture plays a defining role for anisotropy of properties.The research was conducted under financial support of Russian Federation presented by the RF Ministry of Science and Higher Education (Agreement No. 075-15-2021-1352).

Open-cell titanium lattice structures produced by selective laser melting (SLM) are attractive for creation of patient-specific implants with high level of bone ingrowth. In this work, irregular SLM lattice structures made of titanium (cp-Ti) with an average beam thickness of 300 μm and an average porous size of 600 μm were investigated. Optimal processing conditions of SLM for obtaining irregular open-cell cp-Ti lattice structures with mechanical and porous geometry close to human cancellous bone were developed. It was observed that the main parameter of SLM affected on beam thickness is volumetric energy density. Influence of orientation of cubic samples on the construction platform (on the plane, on the edge or on the corner) on properties of lattice structures was investigated. The corner orientation was found to be optimal. It was shown that chemical etching is effective post-treatment method for obtaining required beam thickness and removing the attached powder particles. Optimal chemical etching conditions are the following: etching solution contains 30 mL HNO3 + 45 mL HF + 120 mL water, etching time is 10 s. The elastic modulus and the elastic limit of etched lattice samples are 1.4–1.9 GPa and 44–51 MPa, respectively, which correlates with characteristics of human cancellous bone. Compression of samples during mechanical tests occurred without beams destruction. Corrosion characteristics of obtained etched and non-etched lattice structures in Hank's Balanced Salt Solution (HBSS) have been improved compared with cp-Ti bulk samples. The biological and medical tests of the obtained samples will be carrying out to determine biocompatibility, influence on the growth of bone tissue, permeability, etc.

The use of selective laser melting (SLM) leads to the formation of a complex material structure with high residual elastic stresses. The work investigates the distribution of macrostresses in SLM samples using five different scanning strategies. The stresses were measured by X-ray method and by recording the change in the shape of the specimens as a result of their separation from the platform using digital correlation image method. The combined use of the two methods provides more reliable results for SLM samples. It is shown that depending on the scanning strategy, the nature and magnitude of macrostresses change which are distributed more isotropically and have a smaller value when using scanning strategies with different directions of the laser beam movement.

This article discusses adjustment of processing modes of selective laser melting of powdered 03Kh16N15M3 steel allowing fabrication of lattice structures with steady parameters. On the basis of statistical analysis of sizes of cells, ribs, and nodes in cross section parallel to the growth direction of lattice structures of two sizes of ribs and voids (400 × 1000 and 300 × 600 μm), the process variables providing fabrication of items with the most stable sizes along the height of the structure have been determined. The sizes of the main elements of the lattice structure have been determined using a scanning electron microscope; the crystallographic texture and material structure have been determined using X-ray structural analysis. It has been determined that increase in laser power leads to increase in distortions in crystalline structure and decrease in the lattice constant of the material of lattice structures. The highest distortions of the structure have been detected in ribs of lattice structures as well as in items with smaller sizes of ribs and voids. The material of the considered lattice structures is characterized by axial texture, for which crystallographic axes <100> are oriented parallel to the growth direction. The degree of manifestation of the axial texture component depends on the laser power used for growing of lattice structures. The samples obtained by minimum radiation power are characterized by a scattered axial texture, which is dictated by an increase in the number of chaotically oriented grains with a simultaneous decrease in the bulk of strictly oriented columnar crystals, located mainly in the vicinity of the axis of the ribs of the lattice structure. The texture sharpness in lattice samples with voids of small size is higher than that in samples with voids of large size.

Research into the plastic deformation process in the lattice structure produced by selective laser melting (SLM) of powder from 316L austenitic stainless steel was carried out by compression tests along the build direction and perpendicular to it. The resulting stress–strain curve parameters showed anisotropic behaviour of such a structure. Differences in the crystallographic texture of both the bulk and lattice samples were also discovered, so the direct use of the mechanical properties of the bulk materials for calculation of lattice structure deformation behaviour would be incorrect. To overcome this limitation, the crystal plasticity finite element model based on the DAMASK framework was used, and the mechanical properties of the lattice structure material were calculated with respect to the crystallographic texture differences. In turn, the data obtained for the bulk material was used to model the plastic deformation of the lattice structure and these results are in good agreement with the experimental data. Therefore, it is possible to use the bulk material data for forecasting the lattice structure deformation. The resultant model allows for the prediction of the deformation behaviour of the lattice ribs.

The steel 316L plates formed by selective laser melting of a powder are found to have a sharp texture, which is close to the {001} $$\left\langle {100} \right\rangle $$ cube texture, and the texture intensity and the deflection of texture from external plate directions change across the plate width differently in plates of different thicknesses. The mechanical properties determined by nanoindentation are also nonuniform over the plate width. The nonuniformity of texture and microhardness is assumed to be related to the changes in the plate growth conditions in printing, such as the heating and cooling rates, the direction of laser beam action, the heat removal direction in plates of different thicknesses, and the shape of the molten pool. The crystallographic texture is shown to be a sensitive indicator of all plate growth processes; therefore, it can be used to optimize the parameters that determine the properties of the plates.

This research looked at specimens made of austenitic steel 316L by Selective Laser Melting (SLM) and designed for tensile testing in different directions (in relation to the growth direction during printing). A significant anisotropy of mechanical properties was found as a result of mechanical testing: anisotropy of the yield strength is 1.13; tensile strength - 1.10; elongation - 1.84. X-ray analysis of the texture helped understand how the crystallographic texture of the specimens changed under elongation in different directions. On the basis of strain-induced re-orientation of grains it was established that the active deformation mechanism included crystallographic slip of type {111}<110>. Depending on the orientation of stress to the internal crystallographic axes, different texture components form as a result of elongation leading to the observed anisotropy of mechanical properties. To understand how changes in the crystallographic texture influence the mechanical properties of SLM products, a model has been developed for simulating anisotropy of mechanical properties on the basis of texture analysis data using DAMASK software. The input data include grain orientation, active deformat ion mechanism and parameters of the phenomenological law describing hardening of slip systems. A good correlation was found between the simulation data and the results of elongation obtained for experimental specimens printed at different orientation to the growth direction, in terms of both the yield strength anisotropy and I he strain-induced changes in the crystallographic texture. Thus, knowing the difference in the crystallographic texture. The results of mechanical testing of standard shape specimens can be used to define the properties of specimens of a different shape.

Selective laser melting (SLM) is an additive manufacturing technique, which allows varying the relative porosity at the micro and macro levels. In this study, the microstructure, including the porous structure, of cp-Ti Grade 1 ELI produced by SLM and the effect of the scanning parameters on mechanical properties are studied. The mechanical properties are analyzed in terms of ISO 5832-2 for metal implants for surgery. The cp-Ti samples processed by SLM are characterized by increased strength due to the low porosity condition and the acicular martensitic structure. The ductility data scattering is explained by the stratified distribution of porosity in the metal after SLM.

In this work we consider obtaining high-density powder samples from austenitic stainless steel 316L, on the first national experimental layered build-up equipment by the method of selective laser melting (SLM) Melt Master3D - 550. The equipment description is given. Morphometric properties of the original powdered material is studied. Continuous unit vectors (tracks) and high-density samples with the relative density of 97% are obtained during the experiments. The laser radiation energy contribution is estimated to compare the conditions for obtaining samples with different technological parameters. In course of the study of the sample properties the dependence of density on the specific energy is revealed. Moreover, the influence of technological parameters on the microstructure and microhardness of the samples is established. The obtained data are compared with the results of other studies on similar foreign facilities.

The new approach in developed plasma methods consists in that dispersion-hardening additives (TiC, TiB2 in particular) are not mechanically added to powder mixture as additional component, as in conventional methods, but are instead synthesized during high voltage electric discharges (HVED) in disperse system "hydrocarbon liquid - powder"; preservation of ultrafine structure is ensured due to use of spark plasma sintering (SPS) as a consolidation method. HVED in disperse system "hydrocarbon liquid - powder" due to impact of plasma discharge channel, electromagnetic fields, shock waves mechanical impact, hydro flows and volume microcavitation leads to synthesis of nanocarbon, metal powders dispersion and synthesis of micro- (from 10(-6) to 10(-7) m) and nanosized (from 10(-7) to 10(-9) m) composite powders of hardening phases. SPS is the passage of pulsed current (superposition of direct and alternating current) through powder with the simultaneous mechanical compressing. The formation of plasma is initiated in gaseous phase that fills gaps between particles. SPS allows targeted control of grain growth rate and thus allows obtainment of multifunctional composite materials dispersion hardened by nanoparticles. Processes of HVED synthesis of micro- and nanosized powders of new compositions from elemental metal powders and their mixtures with the subsequent application of high-speed SPS of obtained powders create conditions for increase of strength (by 10 - 20 %), hardness and wear-resistance (by 30 - 60 %) of obtained materials.

The method of bend testing annular specimens produced by pulsed high-voltage resistance welding of a packet of thin annular sheets made of 49K2FA alloy is described. The ring is loaded with a compressive force applied to the plane of the ring. The results of tests of four annular specimens with the simultaneous application of the method of digital correlation of the images for recording the displacement field and visualizing the strain fields in the loaded object are presented. The test results indicate that the specimens separate into individual elements prior to failure with the loss of stability in the stage of elastoplastic loading. The possibilities of reaching a relatively high level of strength and resistance to delamination in the elastic loading stage are indicated. The problem of bending of the ring is solved by the finite element method using the ANSYS program. It is shown that the experimental results and numerical analysis data are in good agreement.

This research analyses the influence of the parameters of high-voltage electric pulse welding on microstructure of weld seams and mechanical parameters of samples. Special tooling was developed for the process of high-voltage electric pulse welding, allowing welding of ring samples. The method of determination of mechanical characteristics of toroidal samples was developed. An influence is established of parameters of high-voltage electric pulse welding, such as current density and applied pressure, on microstructure of a weld seam and density of a weld joint. The study of magnetic parameters of samples is conducted.

In this paper, the patterns forming a gradient structure with high-electro-consolidation (HEPC) carbonyl iron were identified. Map compactibility carbonyl iron powder was built. According to the table density plot the density of the samples on the parameters of sintering at constant pressure and discharge voltage. Experimental data on the density distribution across the sample were obtained.

Refractory oxide dispersion strengthened 13Cr-2Mo steel powder was successfully consolidated to near theoretical density using high voltage electric discharge compaction. Cylindrical samples with relative density from 90% to 97% and dimensions of 10 mm in diameter and 10–15 mm in height were obtained. Consolidation conditions such as pressure and voltage were varied in some ranges to determine the optimal compaction regime. Three different concentrations of yttria were used to identify its effect on the properties of the samples. It is shown that the utilized ultra-rapid consolidation process in combination with high transmitted energy allows obtaining high density compacts, retaining the initial structure with minimal grain growth. The experimental results indicate some heterogeneity of the structure which may occur in the external layers of the tested samples due to various thermal and electromagnetic in-processing effects. The choice of the optimal parameters of the consolidation enables obtaining samples of acceptable quality.

The densification of electrically conductive powders by high voltage consolidation is studied. High voltage consolidation method (HVC) includes the simultaneous exposure of a powder sample to mechanical pressure (50–500 MPa) and to a short (less than 300 ms) high voltage (above 1 kV) electric discharge with the pulse current amplitude of a few hundred kA/cm2. The densification kinetics of industrial iron powder is analyzed by ultra-rapid video-recording. The integral temperature of the sample has a maximum value at the beginning of the densification process. The compaction process lasts less than 16 ms for all the values of the parameters studied. The shortness of the densification process in comparison with the cooling of the sample provides a constant temperature throughout the entire compaction process. Based on the analysis of the obtained experimental results a mathematical model of high rate wave mode compaction of a powder material under conditions of HVC is formulated. The constitutive equation of the mechanical behavior of the consolidated material accounts for the plastic flow of powder particles and for the collapse of the inter-particle pores. The numerical simulation results reveal optimal values of the dimensionless parameters controlling the HVC process.

Oxide dispersion strengthened 13Cr-2Mo steel powder was successfully consolidated using high voltage discharge compaction to near theoretical density. Such rapid process in combination with high transmitted energy allows obtaining high density of the compacts, saving initial structure with minimal grain growth. Heterogeneity of the structure may occur in the boundary layers of the sample due to thermal and electromagnetic effects but the choice of optimal parameters of consolidation allows obtaining samples of acceptable quality.