Selective Electron Beam Melting Research Articles

Effect of Aqueous Electrolyte Composition on Efficiency of Electrochemical Post-Processing of Additive Manufacturing Products from Ti-6Al-4V Alloy Obtained by Selective Electron Beam Melting

The influence of the anionic composition of an aqueous electrolyte on the efficiency of the electrochemical leveling of the initial microgeometry of samples obtained by the selective electron beam melting (SEBM) at the following mode parameters was studied: current density – 20 A/cm2, initial interelectrode gap – 0.3 mm, average speed of electrolyte pumping – 12 m/c. Aqueous solutions of sodium chloride, nitrate, perchlorate and bisalt electrolytes based on them were studied. It was that aqueous solutions of sodium perchlorate have the best microleveling properties among the studied working media, which provides the ability to reduce the parameters Ra and Rz from values of 35 and 180 μm, respectively, to values of 3.2 and 20 μm during electrolysis of 30 s in a direct-flow electrolyzer. It was established that the microgeometry leveling corresponds to the model of the secondary distribution of dissolution rates; two main factors were identified that significantly influenced on the result: polarization of the electrodes and a decrease in the oxidation state of metal ions passing into the solution during electrochemical machining in the vicinity of the depression in relation to the protrusion due to changes in the local conditions of electrolysis. Microetching along grain boundaries in the studied electrolytes was not detected at the accepted parameters of the electrolysis mode.

Microstructural evolution and dynamic recrystallization mechanisms of additively manufactured TiAl alloy with heterogeneous microstructure during hot compression

Microstructural evolution and dynamic recrystallization (DRX) mechanisms of a Ti−48Al−2Cr−2Nb (at.%) alloy prepared by selective electron beam melting (SEBM) during hot deformation at 1150 °C and 0.1 s−1 were investigated by hot compression tests, optical microscope (OM), scanning electron microscope (SEM), electron back-scattered diffraction (EBSD) and transmission electron microscope (TEM). The results show that the initial microstructure of the as-SEBMed alloy exhibits layers of coarse γ grains and fine γ+α2+(α2/γ) lamellar mixture grains alternately along the building direction. During the early stage of hot deformation, deformation twins tend to form within the coarse grains, facilitating subsequent deformation, and a small number of DRX grains appear in the fine-grained regions. With the increase of strain, extensive DRX grains are formed through different DRX mechanisms in both coarse and fine-grained regions, involving discontinuous dynamic recrystallization mechanism (DDRX) in the fine-grained regions and a coexistence of DDRX and continuous dynamic recrystallization (CDRX) in the coarse- grained regions.

Exploring the optimal mechanical properties of triply periodic minimal surface structures for biomedical applications: A Numerical analysis

Currently, cutting-edge Additive Manufacturing techniques, such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM), offer manufacturers a valuable avenue, especially in biomedical devices. These techniques produce intricate porous structures that draw inspiration from nature, boast biocompatibility, and effectively counter the adverse issues tied to solid implants, including stress shielding, cortical hypertrophy, and micromotions. Within the domain of such porous structures, Triply Periodic Minimal Surface (TPMS) configurations, specifically the Gyroid, Diamond, and Primitive designs, exhibit exceptional performance due to their bioinspired forms and remarkable mechanical and fatigue properties, outshining other porous counterparts. Consequently, they emerge as strong contenders for biomedical implants. However, assessing the mechanical properties and manufacturability of TPMS structures within the appropriate ranges of pore size, unit cell size, and porosity tailored for biomedical applications remains paramount. This study aims to scrutinize the mechanical behavior of Gyroid, Diamond, and Primitive structures in solid and sheet network iterations within the morphological parameter ranges suitable for tasks like cell seeding, vascularization, and osseointegration. A comparison with the mechanical characteristics of host bones is also undertaken. The methodology revolves around Finite Element Method (FEM) analysis. The six structures are originally modeled with unit cell sizes of 1, 1.5, 2, and 2.5 mm, and porosity levels ranging from 50% to 85%. Subsequently, mechanical properties, such as elasticity modulus and yield strength, are quantified through numerical analysis. The results underscore that implementing TPMS designs enables unit cell sizes between 1 and 2.5 mm, facilitating pore sizes within the suitable range of approximately 300–1500 μm for biomedical implants. Elasticity modulus spans from 1.5 to 33.8 GPa, while yield strength ranges around 20–304.5 MPa across the 50%–85% porosity spectrum. Generally, altering the unit cell size exhibits minimal impact on mechanical properties within the range above; however, it's noteworthy that smaller porosities correspond to heightened defects in additively manufactured structures. Thus, for an acceptable pore size range of 500–1000 μm and a minimum wall thickness of 150 μm, a prudent choice would involve adopting a 2.5 mm unit cell size.

Defects, microstructure and associated mechanical properties of Inconel 718 fabricated by selective electron beam melting

Comprehensive characterizations and evaluations were conducted on the relationship between process parameters and density in the Inconel 718 (IN718) alloy fabricated by selective electron beam melting (SEBM). Additionally, the microstructure and anisotropy of tensile properties were evaluated in both the as-built state and after solution treatment and aging (STA). During different stages of energy density, the primary contributors to the porosity rate transitioned from the lack of fusion (LF) pores to the inclusion of spherical and shrinkage pores, resulting in a maximum relative density of 98.95 %. The as-built parts displayed notable parallel texture to the building direction, and a significant tensile anisotropy supported by the Taylor factor. The matrix of these parts consisted of δ, γ', γ″, and carbonitrides, with a considerable presence of δ precipitation leading to a reduction in γ″ content and lower strength. After heat treatment, the δ dissolved, and γ″ precipitated extensively, while the carbonitrides and texture were retained. However, unique tensile results contradicting the predictions made by computational modeling were observed, we propose a new insight attributed to the presence of shrinkage pores along the build direction and use finite element analysis to support this view.

Process optimization and tribological behavior of Ti-48Al-2Cr-2Nb prepared by selective electron beam melting

Selective electron beam melting (SEBM) technology was utilized to fabricate TiAl alloys which possess low density and excellent high-temperature performance, to achieve lightweight design of automotive engines. The forming process of Ti-48Al-2Cr-2Nb was systematically optimized, and found that the microstructure of TiAl formed by SEBM consisted of a layer of alternating γ-band structure and duplex-like structure. As the energy density increases, grain coarsening, proportion increasing of high angle grain boundaries, and anisotropy strengthening occur successively. The forming quality of TiAl reaches its peak at an energy density of 22.5 J/mm3, at which point its mechanical properties and wear resistance also perform the best. Subsequently, in-depth friction experiments at high and room temperatures were conducted, and it was found that at room temperature, as the load increased, the friction coefficient of the samples decreased and the wear rate increased. In addition, the friction coefficient decreases from 0.54 to 0.44, while the wear rate increases from 19.90×10−5 mm3/(N·m) to 25.97×10−5 mm3/(N·m). At this point, abrasive and adhesive wear were the main wear mechanism. Under high temperature conditions, the wear mechanism of the substrate is mainly abrasive wear, adhesive wear, and oxidative wear. And the friction coefficient decreases from 0.69 to 0.49. At lower temperatures, the detached debris was filled and solidified on the wear marks under the action of the friction ring, forming a hardened layer called “enamel”, which can alleviate the negative effects of wear. Under the influence of extreme high temperature environment, the unworn surface forms a light blue oxide film due to rapid oxidation, known as the “burning blue” phenomenon. Along with the high-temperature oxidation phenomenon confirmed by EDS, the oxide layer is more prone to peeling off and forming debris. In addition, melting softening occurs inside the annular wear scar, which increases the amount of deformation under external force, ultimately leading to a significant increase in wear.

Application of 3D-printed individualized porous tantalum buttress in shelf acetabuloplasty for developmental dysplasia of the hip

Shelf acetabuloplasty is a viable treatment for developmental dysplasia of the hip (DDH), yet autologous bone grafts have faced challenges such as morphological mismatch, imprecise placement, and long-term graft resorption. The rapid advancement of three-dimensional (3D) printing technology in orthopedics has enabled the acquisition of digital image correlation method (DICM) data from patient pelvic to bilateral femoral proximal regions through computed tomography (CT) scans. This data is then utilized by software to create 3D models and design individualized metal implants. Using tantalum-based TA1 type I spherical powder as the raw material, a porous tantalum buttress with a pore size of 600 microns and a porosity of 75% was fabricated employing the selective electron beam melting (SEBM) technology. Our Center has applied this 3D-printed individualized porous tantalum buttress in shelf acetabuloplasty for 21 DDH patients (25 hips), including 6 males and 15 females, with a mean age of (21.38±7.39) years. The follow-up period ranged from 12 to 47 months, averaging (22.64±10.86) months. At the final follow-up, patient-reported outcomes (PROs) were used to assess patient’s subjective feelings. Significant improvements were observed in the Non-Arthritic Hip Score (NAHS), modified Harris Hip Score (mHHS), Hip Outcome Score-Sports Subscale (HOS-SSS), International Hip Outcome Tool-12 (iHOT-12), and Visual Analog Scale (VAS) compared with preoperative levels (P<0.01). Radiographic assessments showed that postoperative lateral center edge (LCE) angle, Tonnis angle, acetabular angle (Sharp’s angle), and femoral head coverage all trended towards normal, with statistically significant differences (P<0.01). There was no implant displacement or bone resorption in any case, and no progression in Tonnis grading for hip osteoarthritis (OA) was noted postoperatively, with an 84% patient satisfaction rate. The early follow-up results of 3D-printed individualized porous tantalum buttress in shelf acetabuloplasty are satisfactory, indicating a reliable application prospect for the treatment of DDH patients.

Numerical Study of Temperature Field and Melt Pool Properties during Electron Beam Selective Melting Process with Single Line and Multiple Line Scanning

Numerical Study of Temperature Field and Melt Pool Properties during Electron Beam Selective Melting Process with Single Line and Multiple Line Scanning

Effect of surface topography on the fatigue behavior of additively manufactured Ti6Al4V and CoCr alloys

Powder bed fusion (PBF), including selective laser melting and electron beam melting, fabricates complex, porous, osseointegrative implants for widespread clinical use. Fatigue testing is imperative for predicting long-term strength and durability of rough and surface porous implants while bone remodels around and grows into the implant. This study analyzes different materials (Ti6Al4V and Co28Cr6Mo) with varying topographies including as-printed surface roughness and the addition of a surface porous layer common to implants. The results are compared to wrought and PBF controls that are polished and machined. Moreover, different PBF techniques for titanium result in different as-printed surface roughness (∼0.07–17 μm) and microstructure. The fatigue data demonstrates that the surface finish impact was stronger in Ti6Al4V versus CoCr and SLM Ti6Al4V HIP + surface porous gyroid samples didn't perform worse than the roughest solid sample without surface porosity (EBM Ti6Al4V). With the same mechanical surface finishes, the SLM and wrought Ti6Al4V samples display similar fatigue resistance (800 and 850 MPa respectively), while EBM samples remain inferior (350 MPa). This study provides a foundation to compare fatigue resistance across materials and surface topographies through different fabrication techniques to optimize the lifespan of orthopedic implants while incorporating rough as printed surfaces and added surface porosity, both of which are essential for osseointegration.

Microstructure and mechanical behaviors of electron beam melted Ta10W alloy

TaW refractory alloys with excellent high-temperature mechanical behaviors up to 2000 ℃ have been intensively researched recently. Such performances herald great potential in industrial applications. In this study, we manufactured a Ta10W refractory alloy using selective electron beam melting with elemental TaW powder. The as-received microstructure shows high chemical homogeneity, and the obtained hardness values are 295±3 HV and 293±3 HV for XOY and XOZ planes, respectively. The yield strength of the compression tests can reach 664±8 MPa. The yield strength, ultimate tensile strength, and strain after fracturing of samples normal to the build direction of the as-deposited Ta10W refractory alloy are 750±5 MPa, 764±4 MPa, and 6.05±2.34, respectively. This study comprehensively investigated the microstructure and mechanical behaviors of the additively manufactured Ta10W refractory alloy, which can provide considerable insight into additive manufacturing of high-melting point refractory alloys.

Porosity of Additive Manufacturing Products Obtained by Selective Electron Beam Melting

The paper presents some investigation results of the material porosity of the samples made using the techno-logy of selective electron beam melting from the Ti-6Al-4V alloy powder. The influence of hatching mode parameters on the porosity of samples was carried out using optical microscopy and X-ray computed tomography. A qualitative and quantitative assessments of the shape and size of pores have been made, and technological factors contributing to their appearance have been identified. It has been established that discontinuities of large sizes are formed mainly in the area of overlapping contouring and hatching zones at a distance of 0.2÷2 mm from the sample surface. Selective selection of pores in the surface layer was not detected. It was found that in the range of linear electron beam energy densities of 180÷300 J/m, the minimum porosity is achieved within that range.

Assessment of Mechanical Behavior in H13 Tool Steel Synthesized through Electron Beam Melting and Selective Laser Melting Techniques

Assessment of Mechanical Behavior in H13 Tool Steel Synthesized through Electron Beam Melting and Selective Laser Melting Techniques

Hot deformation behavior of a layered heterogeneous microstructure TiAl alloy prepared by selective electron beam melting

TiAl-based alloys are known for their exceptional high-temperature properties but suffer from low hot workability. The emergence of additive manufacturing (AM) technology significantly decreases the workability requirement, while the microstructure heterogeneities in AMed TiAl are troublesome. This paper explores the hot deformation behavior and microstructure evolution of a layered heterogeneous microstructure TiAl alloy prepared by selective electron beam melting. The Arrhenius constitutive model with strain compensation was established, and hot processing maps were constructed. The microstructure showed that at the initial stage of deformation, a large number of dislocation slips occur preferentially in the soft coarse-grained layers. With the increase of strain, dislocation accumulation in heterogeneous interfaces, and dynamic recrystallization (DRX) occurs. Eventually, the coarse-grained region is constantly occupied by fine DRX grains. A high density of deformation twins at high strain rates further promotes the formation of tiny DRX grains. When the hot compression temperature reaches 1200 °C, the initial alternative fine-grained and coarse-grained hetero-structure transforms into duplex (DP) and near-lamellar (NL) microstructure, and microstructure heterogeneity is eliminated. The results enhance understanding of the hot deformation behavior of heterogeneous microstructure TiAl alloys.

Electrochemical processing of parts from Ti—6Al—4V alloy by additive manufacturing

The process of alignment of the initial microgeometry of samples obtained by the method of selective electron beam melting (EBM) by electrochemical etching in aqueous solutions of NaCl under current density 20, 30 and 40 A/cm2 was studied. The possibility of reducing the parameters Ra and Rz from the values of 35 and 180 µm, respectively, to the values of 7.2 and 33 µm during the electrolysis time of 40 s under galvanostatic conditions with the removal of the allowance of 210 µm is shown. Keywords:selective electron beam melting, surface roughness, high speed electrochemical dissolution katusha0112@yandex.ru, morgunov56@mail.ru, sbp47@mail.ru, iliaslusar42@yandex.ru, smsergei1@yandex.ru

Mechanical and Electrochemical Properties Comparison of Additively Manufactured Ti-6Al-4V Alloys by Electron Beam Melting and Selective Laser Melting

This work involves additively manufactured Ti-6Al-4V alloys, which are widely used in automobile, biomedical, and aircraft components for a comparison of the microstructure–properties relationship between electron beam melted (EBM) and selective laser melted (SLM) alloys after hot isostatic pressing treatment. We carried out microstructural, mechanical, and electrochemical measurements on both alloys. They showed comparable α and β phase contents with slightly higher lattice parameters in the EBM sample compared to the SLM. The EBM sample showed higher yield strength and uniform elongation due to the activation of multistage defects-driven strengthening and strain hardening mechanisms. Cracking during the tensile test nucleated mainly at the α phase near high-mechanical mismatch α/β interfaces. This mechanism was consistent with the reported generation of hetero-deformation-induced strengthening and strain hardening. Both alloys showed similar electrochemical behavior, but the SLM sample was more susceptible to corrosion than the EBM alloy.

Effect of Heat Treatment on the Structure and Properties of Titanium Aluminide Alloy Ti–Al–V–Nb–Cr–Gd Produced by Selective Electron Beam Melting

Effect of Heat Treatment on the Structure and Properties of Titanium Aluminide Alloy Ti–Al–V–Nb–Cr–Gd Produced by Selective Electron Beam Melting

Creep behavior and creep-oxidation interaction of selective electron beam melted Ti–48Al–2Cr–2Nb alloy at different temperatures

In this work, creep behavior and creep-oxidation interaction behavior of Ti–48Al–2Cr–2Nb alloy fabricated by selective electron beam melting at different temperatures were investigated in detail. This alloy exhibits a near-γ microstructure composed of coarse/fine mixed equiaxed grains. Creep test results show that creep behavior of this alloy is sensitive to temperature. This is mainly manifested in that creep life reduces significantly by 84.8 % as temperature increases from 800 °C to 850 °C. During creep, discontinuous dynamic recrystallization characterized by grain nucleation and growth and continuous dynamic recrystallization characterized by strain gradient and orientation accumulation occur simultaneously. The formation of mechanical twins plays an important role in stimulating dynamic recrystallization. Meanwhile, creep deformation and fracture mechanisms of this alloy at different temperatures were also discussed. On the other hand, oxidation test results reveal that the applied tensile stress has a positive effect on the oxidation behavior of this alloy: the growth of TiO2 oxide is inhibited and the oxidation rate is slowed down. However, under creep-oxidation interaction, the intergranular cracking of the oxide film occurs along with the necking of the alloy matrix during creep.

Anomalous strain rate dependence of ultra-low temperature strength and ductility of an electron beam additively manufactured near alpha titanium alloy

The strain rate (ε˙) dependence of ultra-low temperature strength and ductility was investigated systematically on a cryogenic near alpha titanium alloy Ti-3Al-3Mo-3Zr-0.2Y additively manufactured by electron beam selective melting (EBSM). As ε˙ increases under quasi-static tension at 77 and 20 K, ductility monotonically decreases when yield strength (YS) keeps ascending. As ε˙ increases from 5.6 × 10–4 s−1 once by one order of magnitude, elongation-to-fracture declines from 20.0 % to 16.5 % and 15.7 % at 20 K. However, unlike the regular monotone increase at 298 and 77 K, ultimate tensile strength (UTS) at 20 K rises to 1460 MPa first then drops to 1320 MPa. This study further examined how strain rate affects slipping, twinning and strain hardening behavior. The monotone increase in YS is primarily attributed to the increased CRSS for slips and the enhanced tendency of pyramidal 〈a〉 and 〈c + a〉 slipping and <101¯0 > 34° twinning at 20 K. On the other hand, the monotone decrease of ductility is essentially ascribed to the intensified deformation localization characterized by micro shear bands, multiple necking and single necking. More importantly, the mechanisms of abnormal UTS variation and disappearance of serration flow at 20 K are discussed in terms of strain hardening levels, degree of shear deformation localization and the interaction of slips and twins. This study provides deep insights into strain rate effect on cryogenic mechanical behavior of EBSM-built titanium alloy.

PERSPECTIVES AND DEVELOPMENT TRENDS FOR APPLICATION OF ADDITIVE TECHNOLOGIES IN MODERN DENTISTRY IN THE LIGHT OF INDUSTRY 4.0

Additive manufacturing technologies (AMTs) offer a new approach for cost-effective production of goods and services and are therefore quite rightly included as part of the Fourth Industrial Revolution, Industry 4.0. Last years great attention is paid to the AMTs as technologies of the future development in many countries all over the world including the European Union. Depending on the availability of a good base of installed 3D printers and intellectual potential, the countries are divided into two groups: 1) leaders in the field of 3D printing technology and 2) countries with large bases of equipment, but lack of trained and qualified labor force. The aim of the present paper is to analyze the perspectives and development trends for application of additive technologies in modern dental medicine in the light of Industry 4.0. The constant development of AMTs will accelerate their implementation in various fields and in particular in medicine/dentistry. The 3D printing technologies are first applied in dentistry, due to the possibility for fabrication of individual dental constructions. Currently, almost all worldrenowned companies for production of dental materials and machines develop additive technologies and manufacture the corresponding equipment. According to the forecasts, the 3D printing is expected to be widely used in dental clinics and laboratories in the next 5-10 years. The additive technologies most often applied in dentistry include stereolithography, fused deposition modeling, selective electron beam melting, selective laser melting/sintering and ink-jet printing. The great variety of materials used in these processes allow constructions with different purposes to be made for all areas of dental medicine - surgery, oral implantology, conservative dentistry, orthodontics and prosthetic dentistry.

Study of structure and properties of titanium alloy manufactured by selective electron beam melting using "thin walls" mode

The results of research on the powder from the titanium alloy Ti—6Al—4V, used for selective electron beam melting, are presented. The study reveals the structure and mechanical properties of standard thin samples made from the titanium alloy Ti—6Al—4V using the developed ‘thin walls’ mode. It has been established that the alloy structure obtained through the "thin walls" mode exhibits a Widmansttten structure with low dispersion of α-phase plates. The manufactured samples demonstrate higher strength compared to samples produced using traditional technology.

Mechanical properties characterization of Ti-6Al-4 V grade 5 (recycled) additively manufactured by selective electron beam melting (EB-PBF)

Additive manufacturing, a rapidly expanding technology, enables the production of intricate parts through the successive layering of materials. However, there remains a dearth of research on the viability of incorporating recycled powder into this process, with the potential to decrease expenses and enhance sustainability. This study's objective is to investigate the ramifications of employing recycled Titanium Ti-6Al-4 V alloy powder, for up to ten cycles, without the addition of virgin powder, in the context of additive manufacturing. The findings reveal that the mechanical properties of the material experience an approximate 40 % degradation in comparison to virgin powder. In ultrasonic very high-cycle fatigue tests (VHCF), the failure stress in the Z direction for additive manufacturing EB-PBF equals or surpasses 245 MPa. This research makes a significant contribution to the sustainable advancement of additive manufacturing, as it demonstrates the potential for recycling Titanium Ti-6Al-4 V grade 5 powder for the production of new items. This not only reduces costs but also serves the environment by circumventing unnecessary material disposal. Consequently, the outcomes of this investigation underscore the promising prospects of additive manufacturing with recycled powder, ushering in fresh opportunities for the industry, especially with regards to sustainability and environmental responsibility.