Alloy Deposition Research Articles

A Concentrically Moveable Erosion Zone Magnetron for In Operando Tailoring of Alloy Nanoparticles in a Gas Aggregation Source

AbstractOne particularly interesting approach for the deposition of highly pure nanoparticles (NPs) in a solvent‐ and surfactant‐free process is the gas phase synthesis of nanoparticles using a gas aggregation source (GAS) based on magnetron sputtering. Apart from the possibility of tuning the NP size‐distribution via process parameters, e.g., gas flow, pressure, and aggregation length, multicomponent targets in a GAS enable in operando composition tuning of alloy NPs. However, in the practical application of the GAS, two main challenges have to be addressed: low target utilization and low conversion efficiency. This work describes a magnetron with a concentrically moveable erosion zone (cMEZ magnetron), and showcases its applicability for the deposition of metal (Cu) and metal alloy (CuNi) NPs via GAS. The cMEZ magnetron relies on an in operando reconfigurable outer magnet array, which enables tuning of the position of the erosion zone, impacting target utilization. By weighting the targets and substrates before and after deposition, the conversion efficiency is determined for different operating pressures and magnet configurations. Furthermore, the multicomponent target approach is tested with the cMEZ magnetron, which enabled the in operando composition tuning of the Ni content in CuNi NPs from ≈5 to ≈35 at% only by varying the magnetic field.

Ni-Co alloy supported on CeO2 by SiO2 encapsulation for dry reforming of methane

Dry reforming of methane (DRM) is a highly endothermic reaction that needs harsh condition of high temperature for syngas production, which is challenged by developing catalysts with properties of anti-sintering and low carbon deposition. This work synthesized confined catalysts of (Co-Ni/CeO2)@SiO2 for DRM reaction. The catalysts possessed multifunction including size and alloy effects, metal-support interaction and confinement effect, which contributed to high rates of CH4 and CO2, marginal sintering of NiCo alloy and trace carbon deposition. The (3Ni-3Co/CeO2)@SiO2 catalyst reached rates as high as 4.74 mmol/(gNi·s) and 5.57 mmol/(gNi·s) for CH4 and CO2, respectively, at 1023 K. The rates were keeping stable for at least 36 h on stream. The characterizations of used samples revealed the limited size change of NiCo alloy and the low carbon deposition. The work provides valuable guidance for developing stable catalysts for DRM and other high temperature reactions.

Analysis of Microstructural Transformations Induced by Thermal Aging of Co-Cr-Ni-W-C Alloy Deposits and Their Impact on Corrosion Behavior in a 3.5% NaCl Medium

Analysis of Microstructural Transformations Induced by Thermal Aging of Co-Cr-Ni-W-C Alloy Deposits and Their Impact on Corrosion Behavior in a 3.5% NaCl Medium

Surface modifications to reduce wear in hot extrusion of copper

During hot extrusion of copper, the material tends to stick to the extrusion die due to strong adhesive forces between hot working steel and copper at high temperatures. In this context, surface modifications like nanocomposite coatings deposited by plasma enhanced chemical vapor deposition or boriding of nickel-based alloy 718 (DIN 2.4668) create hard and wear resistant thin solid films that offer high temperature stability. Ti–Si–B–C–N nanocomposite coatings consist of nanocrystalline grains embedded in a thin amorphous matrix. Due to this particular nanostructure, hardness values of up to 39.3 GPa were reached. Boriding of alloy 718 leads to formation of phases consisting of alloying elements like nickel, iron, and chromium and the diffusing element boron. The borides form a boriding zone that offers high hardness. Extrusion of Ø122 mm × 300 mm copper billets preheated to 850 °C was carried out and adhesive wear on tool's surfaces was analyzed. The comparison between hot working steel DIN 1.2367 without surface modification and with Ti–Si–B–C–N coating or borided alloy 718 showed remarkable differences between conventional tools made of hot working steels/alloy 718 and tools with surface modification. A strong decrease particle adhesion was observed.

In-situ induce reinforcement in WAAM of Al-matrix composite using active N2 as shielding gas followed by friction stir processing

Economic and active nitrogen (N2) is used as a shielding gas for the wire-arc additive manufacturing (WAAM) of Al-matrix composite (AMC). Although no crack was found, large flaky nitrides up to 500 μm are generated in the matrix of the Al alloy, leading to a significant deterioration in both plasticity (reduced by 81.4%) and tensile strength (reduced by 17.5%) compared with the deposit protected by argon (Ar), which is to be modified. Then, FSP was performed on the matrix of the Al alloy. The influence of friction stir processing (FSP) on the microstructure and mechanical properties in the stirred zone (SZ) of WAAM 5356 Al alloy deposit, prepared under a N2 environment, was studied. Flaky nitrides were observed in the Al matrix, and were broken due to FSP. The large flaky nitrides with a length of 500 μm were broken into granular nitrides with sizes lower than 2 μm. The grain size in the SZ decreased by 83% after FSP, and the microhardness in the SZ became more uniform, with an average value of 91.9 HV. Owing to the refinement of AlN by FSP, the tensile strength and elongation of the AMC were 349 MPa and 19.9%, much more than that before FSP of 231 MPa and 5.5%, showing an increase of 51.1% and 261.8%, respectively. The plasticity has obvious improvement, which is higher than the common used stir casting AMC.

Microstructure evolution of TC25G/Ti2AlNb structural gradient material fabricated by laser directed energy deposition

Laser directed energy deposition (LDED) is one of the most effective ways to manufacture structural gradient materials. The microstructure changes in transition zone (TZ) and heat-affected zone (HAZ) are often considered to be very important which could affect the mechanical property of the component. In this study, a titanium based gradient material, which is potentially used in high pressure compressor was fabricated by deposition of Ti2AlNb alloy on a forged TC25G alloy substrate. The thickness of the transition zone is around 2000 μm, and the phase transformation from TC25G alloy to Ti2AlNb alloy is followed as: α + β (TC25G alloy) → α + β (Heat affected zone) → α + α2 + B2/β + O (Transition zone) → α2 + B2/β + O (Ti2AlNb alloy). There is no any sudden change of microhardness in the gradient material with the lowest microhardness is found in Ti2AlNb alloy.

Inhibiting sensitivity of microstructure and properties to heat input in DED-arc of 7075 aluminum alloys: The role of TiC-nanoparticles

Achieving high-quality 7075 high-strength aluminum alloy manufactured via directed energy deposition-arc (DED-Arc) remains challenging due to its sensitivity of microstructures and properties to heat inputs. This study examines how TiC nanoparticles can effectively reduce the adverse effects of high heat input from the arc on the surface morphology, microstructure, and properties of 7075 aluminum alloy deposits. The surface morphology, defects, microstructures, and mechanical properties of the deposited alloy parts were characterized. The analysis revealed that reducing the heat input results in smoother surface morphology but has little effect on the number of defects, grain morphology, grain size, and tensile strength. Even under various heat inputs, all deposited samples containing TiC nanoparticles exhibit equiaxed grain structures with an average grain size of approximately 8.98 ± 0.27 μm and possess a tensile strength exceeding 500 MPa with minimal variance. Further studies involving microstructures and computational fluid dynamics suggest that the incorporation of TiC nanoparticles mitigates the impact of thermal dynamic conditions within the molten pool. It was discovered for the first time that there is a significant lattice mismatch of about 18% between the crystal planes of TiC and the Al-matrix in the deposited samples. This mismatch increases the free energy of the growth phase, effectively creating a pinning effect for the growing grains. Consequently, this nanoparticle-induced physical barrier disrupts the conventional control of grain growth dictated by thermodynamic conditions, effectively limiting grain size under various heat inputs by arc. This work demonstrates a promising strategy to reduce the sensitivity of microstructure and properties to heat input during DED processes.

Electrodeposition of Zn[sbnd]Co alloy coatings on carbon steel and their corrosion resistance

The development of ZnCo alloys appeared as alternative for obtaining layers more resistant than the conventional zinc with a minimum increment of cost. The aim of this work is to study the electrodeposition mechanism of the ZnCo alloy on SAE 1020 carbon steel by cyclic voltammetry using two baths with different [Zn2+]/[Co2+] concentration ratios and also to evaluate the corrosion resistance in 0.1 mol L−1 NaCl of electrodeposits obtained potentiostatically using electrochemical techniques as electrochemical impedance spectroscopy, linear polarization resistance and potentiodynamic polarization curves. The voltammograms showed two anodic peaks attributed to dissolution of zinc rich ƞ-phases and cobalt, and a cathodic peak related to ZnCo alloy deposition. The nucleation mechanisms were examined by fitting the experimental data (chronoamperometry) into the Scharifker and Hills nucleation models. Scanning electron microscopy (SEM) showed that the electrodeposits obtained for the [Zn2+]/[Co2+] 9:1 ratio presented a structure in the form of hexagonal platelets in comparison to the electrodeposits with [Zn2+]/[Co2+] 12:1 ratio, which presented cauliflower-shaped structures. On the other hand, the electrochemical techniques proved that the electrodeposits obtained for the [Zn2+]/[Co2+] 9:1 ratio at potential of −1450 mV presented the best anticorrosive properties. Structural and chemical characterization of coatings was accomplished by XRD and XRF.

Crystal plasticity approach for predicting mechanical responses in wire-arc directed energy deposition of NbZr1 refractory alloy

The refractory alloy, such as Niobium-1 wt% Zirconium (NbZr1) alloy, is a promising candidate for diverse applications in extreme environments. This study investigates an integrated experimental and computational methodology that can predict the mechanical properties of wire-arc directed energy deposited (DED) refractory NbZr1 alloy. The effect of large columnar grains with strong texture induced by the wire-DED process has been successfully incorporated into the representative volume element (RVE). Performing crystal plasticity (CP) simulation on RVE of NbZr1, deformation behavior and stress-strain relationship are predicted to explore the process-structure-property (PSP) relationship. The RVE has been created in synthetic microstructure generation software utilizing the grain statistics derived from electron backscatter diffraction (EBSD) analysis, capturing essential microstructural features. A phenomenological constitutive model and appropriate boundary conditions have been applied and solved, using the CP fast Fourier transform method. The CP model has been calibrated and validated utilizing the tensile test data along the build direction and deposition direction, respectively. The error in predicting yield strength and ultimate tensile strength is 0.91% and 0.67%, respectively, for the calibration simulation, whereas these values are 2.51% and 1.81% for the validation simulation. The results suggest strong agreement between the simulation and experimental observation. Even though global deformation behavior remains consistent across multiple RVEs with the same microstructural features, local stress-strain values vary, indicating structural anisotropy, which is also consistent with the digital image correlation (DIC) result. It is proven that this proposed CP method can effectively predict the mechanical responses of components with large grains and strong textures resulting from the wire-arc DED.

Strong compressive γ-TiAl alloy produced by dual-wire-fed electron beam directed energy deposition: Microstructural evolution and strengthening mechanisms

Dual-wire-fed electron beam directed energy deposition (EB-DED) of TiAl alloy is of increasing interest due to its potential to produce high performance components at low cost. However, the strengthening mechanisms involved, in particular the complex relationship between microstructure and mechanical properties, are still unclear. This study uses a combination of experimental fabrication and numerical simulation. The aim is to investigate the microstructural evolution and strengthening mechanisms of a fully columnar γ-TiAl alloy produced by the dual-wire-fed EB-DED technique. The results show that cyclic heating significantly increases the dislocation density in the TiAl alloy. In addition, dislocation networks, twinning intersections and dislocation-twin interactions were observed. Compression test results show that the dual-wire-fed EB-DED prepared γ-TiAl alloy exhibits 26% higher yield strength and fracture toughness, as well as 25% higher work-hardening stress compared to the traditionally processed TiAl alloy of the same composition. The nanoscale twinning and interaction structures are identified as the unique strengthening mechanisms, contributing 194 MPa to yield strength and 1196 MPa to work hardening. This study provides valuable insights into the microstructural characteristics and strengthening mechanisms of TiAl alloy produced using the dual-wire-fed EB-DED.

Influencing mechanisms of melt behavior on metal vapor characteristic and columnar grain formation in wire-arc directed energy deposition of titanium alloy

The metal vapor characteristic and columnar grain formation, influenced by the melt behavior in wire-arc directed energy deposition (WA-DED) of titanium alloy, have great effects on the tungsten electrode contamination and component performance. In this study, a spectroscopic system was adopted to measure the arc temperature and metal vapor distributions, and a multi-physical wire-melt pool model was developed to investigate the wire metal transfer and melt pool convection in WA-DED of titanium alloy. The microstructures of the fabricated components were studied. The influencing mechanisms of melt behavior on the metal vapor characteristic and columnar grain formation, and the tungsten electrode contamination mechanism were revealed. The experimental and numerical results showed that a stable liquid bridge transfer mode was achieved during the WA-DED process. Compared with the one-layer case, the molten metal flow patterns in the multi-layer case were unchanged, but the higher melt temperature caused stronger Ti evaporation; then more Ti vapor entered the arc plasma and absorbed its energy, causing a higher concentration of Ti+ ion in the whole arc region, and thus the arc temperature was decreased. The Ti+ ion can be transported to the negative electrode surface by the cataphoresis, dominating the electrode contamination. Low heat input and high arc force were beneficial to the columnar to equiaxed grain transition.

Development and directed energy deposition of high strength Hf5Mo15Nb35Ta25Ti20 refractory high entropy alloys

In this study, a novel HfMoNbTaTi refractory high entropy alloy was designed by empirical calculations and CALculation of PHAse Diagram (CALPHAD) method by using ThermoCalc software. Directed energy deposition (DED) based additive manufacturing process was used to produce the alloy. After the process parameter determination studies using single-track productions, cuboids were produced. The microstructural investigations showed that while the central region of cuboids has large grains, the outer region has a dendritic structure with some unmolten Mo powders. Although columnar grain formation, which is the general characteristic of directional solidification, was observed at some points, irregularly shaped grains were dominant in the structure. Moreover, there were micron to nano-sized Hf-Ti-O particles inside the grains and especially around the grain boundaries. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses confirmed the formation of disordered body-centered cubic (BCC) Hf5Mo15Nb35Ta25Ti20 alloy with ∼6 vol% of Hf-Ti-O particles. Electron backscatter diffraction (EBSD) analyses indicated that there is a slight texture in the building direction along 〈111〉. In order to determine the stability of these alloys, ex-situ heat treatments coupled with XRD studies were conducted. As opposed to CALPHAD calculations it was not observed any HCP phase formation. Compression test results showed that Hf5Mo15Nb35Ta25Ti20 alloys have high strength (σy = ∼1300 MPa) and high compressive ductility with good strain-hardening ability. Theoretical calculations revealed that the strength of the alloy mainly originated from solid solution strengthening.

Multi-objective optimization of process parameters for laser metal deposition of NiTi shape memory alloy based on neural network and genetic algorithm

Multi-objective optimization of process parameters for laser metal deposition of NiTi shape memory alloy based on neural network and genetic algorithm

Probing dimensional consistency during multi-track multi-layer gas metal arc directed energy deposition of aluminium alloys

Probing dimensional consistency during multi-track multi-layer gas metal arc directed energy deposition of aluminium alloys

Deposition of ultrathick heavy-metal alloys on rotating substrates by high-power impulse magnetron sputtering: Target erosion effects

Sputter deposition of ultrathick (≈20μm) Au–Ta alloy coatings on sphero-cylindrical substrates is key for the fabrication of hohlraums for magnetically assisted inertial confinement fusion. Here, we study the deposition of AuTa4 alloy coatings onto rotating substrates. We use high-power impulse magnetron sputtering (HiPIMS) in a constant peak target voltage mode. Results show that the target erosion state has a strong impact on the dominant crystallographic phase, microstructure, surface morphology, and electrical resistivity of AuTa4 films. This is due to effects of changes in the confining magnetic field with target erosion on the HiPIMS discharge characteristics and the sputter source output. We quantify these effects via plasma diagnostics and discuss the optimization of HiPIMS deposition of ultrathick films for cases when target erosion effects dominate film properties.

Tailoring the nanotwin spacing of Ni-Mo-W alloys via composition and substrate temperature control

Alloy chemistry and deposition conditions can strongly influence the structure and properties of nanostructured materials. However, in Ni-Mo-W alloys, the limited influence of deposition rate on the twin spacing compels the exploration of other routes to tailor the structure and properties. This study was undertaken to investigate the effect of composition and substrate temperature on the nanotwin spacing of sputter-deposited Ni-Mo-W alloys. Increasing the Ni content from 84 at.% to 93 at.% doubled the average twin spacing from 1.8 nm to 3.8 nm, while raising the substrate temperature from room temperature to 200°C for a fixed Ni content of 91 at.% resulted in an increase from 2.9 nm to 5.0 nm. Concurrent weakening of the {111} texture occurred with both increased Ni and temperature. The combined effectiveness of composition and temperature demonstrated here provides a potential process window for tuning the twin spacing while maintaining the strongly textured columnar structure.

In-situ micro-impacting assisted directed energy deposition-arc of aluminum alloy: Formability and microstructure

At present, the in-situ forging devices do not have the ability to flexibly adjust impacting forces over a wide frequency range and cannot be easily integrated, which restricts its application on DED-arc (directed energy deposition-arc) technology for additive manufacturing. A novel method and system of in-situ micro-impacting assisted DED-arc based on a compact high-dynamic linear actuator was proposed, developed and verified in arc deposition of 5B06 aluminum alloy. The terminal impacting head could be sufficiently close to the molten pool to enforce the obtaining of flat surface of the deposited layer. The results show that the in-situ micro-impacting could produce accumulating rapid micro-deformation and thus induce a gradient microstructure. DDRX (discontinuous dynamic recrystallization) and CDRX (continuous dynamic recrystallization) hybrid dynamic recrystallization behavior was observed. The microhardness of impacted samples was increased by 9.5 % and 8.0 % in vertical and horizontal direction, respectively. The process of rapid micro-deformation contributes to the retaining of the in-situ work-hardening effect at high temperatures, which made the proposed in-situ impacting method a preferred option for DED-arc additive manufacturing.

Nanoscale and Tensile-Like Properties by an Instrumented Indentation Test on PBF-LB SS 316L Steel.

The mechanical properties of a defect-free laser melting (PBF-LB) deposit of an AISI 316L steel alloy were assessed by means of an instrumented indentation test (IIT), at both the macro- and nano-scales. The inherent non-equilibrium microstructure of the alloy was chemically homogenous and consisted of equiaxed grains and large-elongated grains (under the optical microscope) with irregular outlines composed of a much finer internal cell structure (under the scanning electron microscope). Berkovich and Vickers indenters were used to assess the indentation properties across individual grains (nano) and over multiple grains (macro), respectively. The nano-indentation over the X-Y plane revealed nearly constant indentation modulus across an individual grain but variable on average within different grains whose value depended on the relative orientation of the individual grain. The macro-indentation test was conducted to analyze the tensile-like properties of the polycrystalline SS 316L alloy over the X-Y and Y-Z planes. The macro-indentation test provided a reliable estimate of the ultimate tensile strength (UTS-like) of the alloy. Other indentation properties gave inconsistent results, and a post factum analysis was, therefore, conducted, by means of a new approach, to account for the presence of residual stresses. The already existing indentation data were supplemented with new repeated indentation tests to conduct a detailed analysis of the relaxation ability of compressive and tensile residual stresses. The developed methodology allows the effect of residual stresses and the reliability of measured macro-indentation properties to be examined as a function of a small group of indentation parameters.

MATHEMATICAL MODELING OF COMPLEX-SHAPED WORKPIECE FORMING FROM ULTRAFINE-GRAINED TI ALLOY AND SUBSEQUENT DEPOSITION OF PROTECTIVE COATINGS BASED ON HIGH-ENTROPY ALLOY

The paper reports on finite element simulation of extrusion of a complex-shaped workpiece made of the ultrafine-grained Ti-6Al-4V alloy and vacuum-arc deposition of a protective coating based on the TiVZrCrAl high-entropy alloy. Temperature fields formed in the workpiece during extrusion are studied. Strain-induced heating and the necessary forming force are determined for the initial temperature-rate conditions. The distribution of strain intensity in the workpiece during extrusion is also analyzed. According to the obtained data, the chosen temperature-rate conditions allow using the ultrafine-grained titanium alloy as the initial workpiece without deteriorating its mechanical characteristics. Computer simulation of the coating deposition on the complex-shaped workpiece provides values of the temperature, chemical composition, and thickness of the high-entropy coating. Thus, the coating thickness is about 6.5-7.5 μm, and the surface heating temperature during the deposition process is within 368-597°C, which allows retaining the ultrafine-grained structure in the alloy.

Development of high strength and lightweight Ti6Al4V5Cr alloy: Microstructure and mechanical characteristics

This article explains development of high strength and lightweight Ti6Al4V5Cr alloy by μ-plasma powder additive manufacturing (μ-PPAM) process for automotive, aerospace, military, dies and moulds, and other similar applications. Microstructure, formation of phases, porosity, microhardness, tensile properties, abrasion resistance, and fracture toughness of multi-layer deposition of Ti6Al4V5Cr alloy are studied and compared with Ti6Al4V alloy. Results reveal that the presence of chromium in Ti6Al4V5Cr alloy refined the grains of its β-Ti and α-Ti phases, increased volume % of β-Ti phase, and promoted formation of its equiaxed grains. It also increased tensile strength, microhardness, abrasion resistance, and fracture toughness of Ti6Al4V5Cr alloy. It enhanced solid solution strengthening and formed higher hardness imparting intermetallic Cr2Ti phase and changed fracture mode to mixed ductile and brittle mode with larger size dimples, cleavage facets, and micropores. But it decreased formation temperature of β-Ti phase and % elongation as compared to Ti6Al4V alloy. Chromium and vanadium content in β-Ti phase of Ti6Al4V5Cr alloy is 7 % and 2.1 % more than its α-Ti phase. This study demonstrates that inclusion of limited amount of chromium content to Ti6Al4V5Cr alloy by μ-PPAM process is very beneficial to enhance microstructure, mechanical properties, crack propagation resistance, and abrasive wear resistance of the Ti6Al4V5Cr alloy. It makes Ti6Al4V5Cr alloy very useful in many commercial applications that require higher strength than Ti6Al4V alloy along with lightweight requirement.