Alloy Powders Research Articles

The influence of the granulometric composition of powders of steels and precision alloys and their melting modes by LPBF ON porosity

The results of the experimental study of powder materials of various brands and classes (stainless steel, precision soft and hard magnetic alloys) are presented, the influence of their parameters (particles, fracture, fluidity, bulk density) on the properties of finite additive samples is evaluated. The impact of melting parameters on the porosity of additive samples has been studied.

Comparative analysis of technological properties and microstructure of titanium powders of different classes of alloys

The results of a study of the technological properties of titanium powders of pseudo-α and pseudo-β alloys are presented. A comparative analysis of the characteristics of powder materials obtained by centrifugal spraying has been carried out. The results of the granulometric composition of the powders were obtained, and the calculation of the spatial packing of particles was applied within the framework of the hard sphere model for various fractional compositions. To compare the microstructure and mechanical properties, test samples from pseudo-α and pseudo-β titanium alloys were obtained using the hot isostatic pressing method according to selected modes.

Preparation and excellent mechanical properties of nanocrystalline GW103K Mg alloy by HDDR technology

Grain size of GW103K Mg alloy powder were markedly refined to about 45 nm from 20 μm by an optimized hydrogenation-disproportionation-desorption-recombination (HDDR) process. By changing temperature, hydrogen pressure and time, the optimum hydrogenation conditions are explored by orthogonal design. Then the complete dehydrogenation process was determined by using single factor control variables. Furtherly, the HDDRed powder was spark plasma sintering (SPS) sintered and hot extruded to prepare GW103K alloy bulk. XRD, OM, scanning electron microscopy (SEM), and transmission electron microscope (TEM) were used to analyze the phase transformation and microstructure evolution, based on which the grain refining mechanism during the HDDR were discussed. The optimum HDDR parameters for preparing nanocrystalline Mg alloy powders are hydriding at 550 °C under 5 MPa hydrogen pressure for 24 h and dehydriding at 550 °C for 8 h in vacuum. The nanocrystalline GW103 alloy presents a notable dimensional stability and the grain size of the alloy bulk is 43 nm after SPS and hot extrusion. As a result, the nanocrystalline GW103K specimens exhibit excellent mechanical properties compared to the coarse-grained counterparts. Especially, the nanocrystalline GW103K alloy has a tensile elongation of 21.1% which is much more than those of the as-cast and as-extrusion alloys.

Optimization of Laser Cladding Process Parameters and Analysis of Organizational Properties of Mixer Liners

Aiming to address the wear and replacement inconvenience of concrete mixer liners, this study utilizes a laser cladding system to clad Fe60 alloy powder on the liner. It investigates the influence of different process parameters on the forming quality of the Fe60 alloy powder cladding layer. The optimal process parameters were obtained by weighted comprehensive evaluation, and single-layer multi-pass cladding experiments were carried out under the optimal process parameters to investigate the effects of a 30%, 40%, and 50% lap rate on the surface flatness and forming quality of the cladding layer. Using a metallographic microscope, a scanning electron microscope analysis of the macro morphology and microstructure of the cladding layer was conducted, a DPT-5 penetration flaw detector was used to observe the cracks on the surface of the multi-channel cladding, a microhardness tester and friction and wear experimental machine were used for the hardness of the cladding layer, and an abrasive wear resistance test was conducted. The results show that under the process parameters of a laser power of 900 W, powder feeding speed of 7 g/min, scanning speed of 600 mm/min, and 50% lap rate, the average microhardness of the fused cladding layer reaches 742 HV, which is 1.8 times higher than that of the liner plate, and the coefficient of friction is 0.57, which improves the liner plate’s wear resistance performance and service life.

Microstructure, hardness and wear resistance of plasma-sprayed and electron beam remelted Ni-Cr-Re coatings on Inconel 625

This paper presents research on the microstructure as well as mechanical properties of electron remelting of air plasma spraying (ASP) layers made of Ni-Cr-Re alloy with varying amounts of rhenium on Inconel 625. Initially, Ni-20 %Cr powder alloys with 10, 20 and 30 % (by weight) rhenium content were prepared and applied to the Inconel by ASP. Then, the air plasma sprayed coatings were remelted by electron beam under different parameters. The remelting by electron beam improved the density and smoothness of the ASP coatings. The remelted coatings were characterized by a dendritic microstructure. Wear tests revealed that the sprayed and electron-remelted coatings had a lower weight loss for higher Re content and that the hardness the remelted coating increased with increasing Re content.

Microstructural Evolution and High‐Temperature Tensile Properties of 15Cr‐Reduced Activation Ferritic Steel Processed by Hot Powder Forging of Mechanically Alloyed Powders

Reduced activation ferritic steels are being explored as possible cladding tube materials for nuclear reactors because of their low activation and excellent irradiation resistance. In the current investigation, reduced activation ferritic steel (Fe–15Cr–2W) is processed by mechanical alloying of elemental powders followed by hot powder forging. Mechanical alloying is carried out in a Simoloyer attritor mill (Zoz GmbH), after which the powders are placed in a mild steel can and forged at 1200 °C in H2 atmosphere. X‐ray diffraction and transmission electron microscopy (TEM) investigation reveal that 10 h of mechanical alloying is required to achieve complete dissolution of Cr and W in the Fe matrix powder. The relative density and hardness distribution of the forged slab is evaluated in longitudinal as well as transverse direction to optimize the powder forging operation. Electron backscatter diffraction analysis showed dynamic recrystallization to take place during the course of hot powder forging. Tensile tests are performed at room temperature as well as at elevated temperatures (600 and 700 °C). The yield strength and ultimate tensile strength at room temperature as well as at elevated temperatures are found to be higher than those reported in literature for reduced activation ferritic steels consolidated by other techniques.

Review of Laser Powder Bed Fusion’s Microstructure and Mechanical Characteristics for Al-Ce Alloys

As a new alloy manufacturing method that can break through the limitations of molds to manufacture fine parts, laser powder bed fusion has recently become a common process for producing aluminum alloys. In the fields of aerospace or automotive, aluminum alloys with both good printability and good mechanical performance in high-temperature conditions are greatly demanded, and the Al-Ce alloy is one of the alloys with significant potential. Therefore, systematic research on the additive manufacturing of Al-Ce alloys is still being explored. Herein, we review the recent progress and current status of laser powder bed fusion-produced Al-Ce alloys, giving our opinions on the development of this alloy system. Element composition, alloy powders, laser powder bed fusion parameters, microstructures, and mechanical properties at room temperature and high temperatures are summarized. The choice of alloying strategies is crucial for a specific mechanical improvement of the Al-Ce alloys. Finally, the details of the Al-Ce alloys manufactured via laser powder bed fusion are presented.

Life cycle assessment of metal powder production: a Bayesian stochastic Kriging model-based autonomous estimation

Metal powder contributes to the environmental burdens of additive manufacturing (AM) substantially. Current life cycle assessments (LCAs) of metal powders present considerable variations of lifecycle environmental inventory due to process divergence, spatial heterogeneity, or temporal fluctuation. Most importantly, the amounts of LCA studies on metal powder are limited and primarily confined to partial material types. To this end, based on the data surveyed from a metal powder supplier, this study conducted an LCA of titanium and nickel alloy produced by electrode-inducted and vacuum-inducted melting gas atomization, respectively. Given that energy consumption dominates the environmental burden of powder production and is influenced by metal materials’ physical properties, we proposed a Bayesian stochastic Kriging model to estimate the energy consumption during the gas atomization process. This model considered the inherent uncertainties of training data and adaptively updated the parameters of interest when new environmental data on gas atomization were available. With the predicted energy use information of specific powder, the corresponding lifecycle environmental impacts can be further autonomously estimated in conjunction with the other surveyed powder production stages. Results indicated the environmental impact of titanium alloy powder is slightly higher than that of nickel alloy powder and their lifecycle carbon emissions are around 20 kg CO2 equivalency. The proposed Bayesian stochastic Kriging model showed more accurate predictions of energy consumption compared with conventional Kriging and stochastic Kriging models. This study enables data imputation of energy consumption during gas atomization given the physical properties and producing technique of powder materials.

Ti-Ta-Cu Biocompatible Alloy System Development via Selective Laser Melting for Prosthetic Applications

This study investigated the development of Ti-Ta-Cu alloys via selective laser melting (SLM) for potential prosthetic applications. Ti-Ta-Cu alloys with 10, 15, and 20 wt.% Ta were fabricated using in situ alloying of elemental powders. We examined the effects of Ta content and SLM processing parameters on microstructure, phase composition, mechanical properties, and corrosion resistance. X-ray diffraction analysis revealed an increase in β-phase content with increasing Ta concentration. Microstructural analysis showed a dendritic structure in Ta-rich areas, with remelting strategies improving chemical homogeneity and Ta dissolution. The Ti-20Ta-5Cu alloy exhibited the best balance of strength and ductility, with an ultimate tensile strength of 1011 MPa and elongation of 5.7%. All compositions demonstrated lower elastic moduli (103–109 GPa) compared to traditional titanium alloys. Microhardness values were highest for Ti-15Ta-5Cu, ranging from 359 to 410 HV0.5 depending on SLM parameters. Corrosion testing in Hank’s solution showed improved pitting resistance for Ti-15Ta-5Cu and Ti-20Ta-5Cu compared to Ti-10Ta-5Cu. The study demonstrates the feasibility of producing Ti-Ta-Cu alloys with tailored properties via SLM, offering potential for customized prosthetic applications with improved biomechanical compatibility and functionality.

Mechanical energy absorption capacity of the porous Ti-6Al-4V alloy under quasi-static and dynamic compression

Porous materials are very efficient in absorbing mechanical energy in different applications. In the present study, porous materials based on the Ti-6(wt.%)Al-4V alloy were manufactured with the use of two different powder metallurgy methods: i) blended elemental powder approach using titanium hydride (TiH2) as well as V-Al master alloy powders and ii) using hydrogenated Ti-6-4 pre-alloyed powder. The powder compacts were sintered with additions of ammonium bicarbonate as a pore-holding removable agent. The emission of hydrogen from hydrogenated powders on vacuum sintering and the resulting shrinkage of powder particles permitted the control of the sintering process and creation of anticipated porous structures. Mechanical characteristics were evaluated under quasi-static and dynamic compressive loading conditions. Dynamic compression tests were performed using the direct impact Hopkinson pressure bar technique. All investigations aimed at characterizing the mechanical energy-absorbing ability of the obtained porous structures. The anticipated strength, plasticity, and energy-absorbing characteristics of porous Ti-6-4 material were evaluated, and the possibilities of their application were also discussed. Based on the obtained results, it was found that porous Ti-6-4 material produced with a blended elemental powder approach showed more promising energy absorption properties in comparison with pre-alloyed powder.

Fabrication of Oxide Dispersion Strengthened Copper Alloy Powders by Atmosphere-Controlled Gas Atomization

Fabrication of Oxide Dispersion Strengthened Copper Alloy Powders by Atmosphere-Controlled Gas Atomization

Transient Liquid Phase Bonding of ZGH451 Superalloy Fabricated by Directed Energy Deposition

ZGH451, a directionally solidified Ni‐based superalloy designed for additive manufacturing, has garnered significant attention in the realm of next‐generation turbine blades. Welding the ZGH451 superalloy is crucial for promoting its practical application. In this study, transient liquid phase (TLP) bonding is applied to weld ZGH451 superalloy produced through directed energy deposition. A Ni‐based interlayer alloy powder is developed and prepared via thermodynamic calculation, with the interlayer subsequently characterized using differential thermal analysis. TLP bonding is conducted at 1200 °C for 4 h. The influence of the preset gap on the joint microstructure and mechanical properties is examined. The microstructure of the TLP bonding joints comprises athermally solidified zones (ASZ), isothermally solidified zones, and diffusion‐affected zones. The ASZ width significantly increases with the growing preset gap. A preset gap not exceeding 100 μm enables complete isothermal solidification of the joints. Particularly, joints with a preset gap ranging from 0 to 30 μm demonstrate optimal reliability, exhibiting a tensile strength of up to 1375 MPa at room temperature, which is 12% higher than the room temperature strength of the base metal (BM), and a tensile strength of 983 MPa at 760 °C, surpassing 86% of the BM's strength at the same temperature.

Development of Cost-Effective Sn-Free Al-Bi-Fe Alloys for Efficient Onboard Hydrogen Production through Al–Water Reaction

Leveraging the liquid-phase immiscibility effect and phase diagram calculations, a sequence of alloy powders with varying Fe content was designed and fabricated utilizing the gas atomization method. Microstructural characterizations, employing SEM, EDS, and XRD analyses, revealed the successful formation of an incomplete shell on the surfaces of Al-Bi-Fe powders, obviating the need for Sn doping. This study systematically investigated the microstructure, hydrolysis performance, and hydrolysis process of these alloys in deionized water. Notably, Al-10Bi-7Fe exhibited the highest hydrogen production, reaching 961.0 NmL/g, while Al-10Bi-10Fe demonstrated the peak conversion rate at 92.99%. The hydrolysis activation energy of each Al-Bi-Fe alloy powder was calculated using the Arrhenius equation, indicating that a reduction in activation energy was achieved through Fe doping.

Synthesis and Characterization of Ti-13Ta-6Sn Foams Produced Using Mechanical Alloying, the Space Holder Method and Plasma-Assisted Sintering

Highly porous titanium foams are great candidates for replacing bone structures with a low elastic modulus owing to their ability to avoid the stress shielding effect. However, the production of highly porous foams (>70 vol.%) with well-distributed, stable, and predictable porous architectures using powder compaction and space holders is challenging. In this study, pure titanium powder and mechanically alloyed Ti-13Ta-6Sn were mixed with 50, 70, and 80 vol.% KCl powders as a space holder, cold-compacted, and sintered in a plasma-assisted sintering reactor to produce highly porous foams. The space holder was completely removed using heat and plasma species collisions prior to sintering. A Ti-13Ta-6Sn alloy powder with α, β, and metastable FCC-γ phases was synthesized. The characteristics of the alloyed powder, mixing step, and the resulting sintered samples were compared to those of CP-Ti. After sintering, the alloy exhibited α and β phases and a reduced elastic modulus. Foams with an elastic modulus in the range of the cortical and trabecular bones were obtained. The results showed the effects of the space holder volume fractions on the volume fraction, size, distribution, interconnectivity, and shape of the pores. The Ti-13Ta-6Sn foams exhibited a uniform open-celled porous architecture, lower elastic modulus, higher yield strength, and higher passivation resistance than CP-Ti. Ti-13Ta-6Sn exhibited a nontoxic effect for the mouse fibroblast cell line.

Enhanced Combustion Properties of Al-Si Eutectic Alloy in Energetic Mixtures

This study investigates the feasibility of using an Al-Si eutectic alloy as a reactive fuel in energetic mixtures. Al-Si eutectic alloy powders were obtained from secondary resources and ground to a particle size of less than 100 μm. We examined these powders’ burning characteristics and thermal properties compared to pure Al powder. Results showed that the burning rate of energetic mixtures containing Al-Si eutectic alloys was 1.5 to 2.0 mm/s higher than those with pure Al. Additionally, the activation energy of pure PTFE was reduced from 81.29 kJ/mol to 61.75 kJ/mol when the Al-Si alloy was added. The formation of oxides, carbides, and fluorides in the combustion products of Al-Si-based mixtures significantly influenced their thermodynamics.

Optimum Oxygen Concentration in Powder Bed Fusion Using Laser Beam for Building of Sc-containing Aluminum Alloy Powder.

Optimum Oxygen Concentration in Powder Bed Fusion Using Laser Beam for Building of Sc-containing Aluminum Alloy Powder.

Microstructures and properties of a novel cemented carbide prepared using a Co–Ni–Cu multiprincipal element alloy as the binder

A Co–Ni–Cu multiprincipal element alloy (MPEA) powder was successfully synthesized through coprecipitation. Results of energy dispersive spectroscopy (EDS) and X-ray fluorescence spectroscopy (XRF) revealed nearly equal atomic ratios for Co, Ni, and Cu in the Co–Ni–Cu MPEA powder. Moreover, X-ray diffraction (XRD) confirmed a single-phase face-centered cubic (fcc) structure in the Co–Ni–Cu MPEA powder. To explore the differences in microstructure and mechanical properties, we compared a novel WC–2Co–2Ni–2Cu cemented carbide, utilizing the Co–Ni–Cu MPEA as a binder, with conventional WC–6Co and WC–3Co–3Ni cemented carbides prepared via liquid phase sintering. This comparison was conducted using scanning electron microscopy, XRD, and mechanical properties testing. Observations revealed that the surfaces of WC grains in WC–2Co–2Ni–2Cu and WC–6Co appeared smooth and flat, while those in WC–3Co–3Ni exhibited roughness with numerous terraces. In addition, the average grain size was 0.96, 1.14, and 1.22 μm in WC–2Co–2Ni–2Cu, WC–6Co, and WC–3Co–3Ni, respectively. Notably, the Co–Ni–Cu MPEA inhibited WC grain growth. WC–2Co–2Ni–2Cu (1388 HV30) exhibited hardness similar to that of WC–6Co (1406 HV30) but the highest fracture toughness (9.04 MPa∙m1/2), while WC–3Co–3Ni (1332 HV30) presented the lowest hardness. Bending strength values were recorded at 2406 MPa for WC–2Co–2Ni–2Cu, 2816 MPa for WC–6Co, and 2645 MPa for WC–3Co–3Ni, with WC–6Co exhibiting the highest bending strength. Considering their microstructures, physical properties, and mechanical properties comprehensively, the novel cemented carbides exhibited only slightly reduced bending strength compared to conventional counterparts. Thus, the Co–Ni–Cu MPEA binder demonstrates promising potential as a replacement for the conventional Co metal binder.

Experimental and simulation studies to optimize the mechanical alloying process of ODS-FeCrAl alloy powder

Oxide dispersion strengthened (ODS) FeCrAl alloy exhibits superior mechanical qualities at high temperatures and resistance to neutron irradiation, making it a highly promising material for accident-tolerant fuel cladding. The preparation of ODS-FeCrAl alloy powder by mechanical alloying can mix Y2O3 and FeCrAl alloy powder uniformly and promote the uniform dispersion of nanoscale oxide particles in the alloy matrix. The preparation of ODS-FeCrAl alloy powder by the mechanical alloying method is greatly influenced by the rotational speed. Therefore, this study uses a combination of experiments and numerical simulation to investigate the effects of different rotational speeds on the microscopic morphology, particle size and force of alloy powder during the ball milling process. The mechanically alloyed powder was subjected to XRD inspection to determine the optimum ball milling time at each rotational speed by means of the maximum lattice distortion, and then the powder micromorphology and particle size were analyzed. Then the forces on the powder and grinding ball during the ball milling process were analyzed by numerical simulation, and it was found that the collision force and normal force played a dominant role in the ball milling process. The combined experimental and simulation results determined that the ODS-FeCrAl alloy powder obtained by ball milling at 300 rpm for 35 h had the largest lattice distortion, fine grain size and uniform particle size, which achieved the best mechanical alloying effect.

Microstructure and magnetic properties of surfactant-assisted ball milling NdFe8Co2Mo2 powders and their nitrides

The NdFe8Co2Mo2 alloy ribbons were prepared by melt-spinning. The powder was prepared through surfactant-assisted ball milling, followed by nitriding to produce the NdFe8Co2Mo2Nx alloy. The alloy ribbons grain size decreases as the copper roller speed increases. At the speed of 30 m/s, a pure 1:12 phase alloy ribbons were produced. The grain size decreases with increasing the ball milling time, but the composition phases almost unchanged of the alloy powder. The grain size refine after nitriding, but the grain volume expands when the nitriding temperature exceeds 500 °C. With increasing ball milling time and nitriding temperature, the remanence (Mr) and coercivity (Hc) of the alloy powder increase first and then decrease. The alloy powder obtained from ball milling for 3 h after nitriding at 475 ℃ for 3 h, resulting in Mr was 44.43 Am2/kg, Hc was 0.434 T, and saturation magnetization (Ms) was 74.89 Am2/kg.

Cu-Al-Ni Nanocrystalline Compacts Obtained by Spark Plasma Sintering of Mechanically Alloyed Powders.

The aim of this work is to obtain Cu-13.5Al-4Ni alloy for use as shape memory alloy by Spark Plasma Sintering (SPS) of mechanically alloyed powder. The study investigates the structural and microstructural changes in terms of crystal parameters, crystallite sizes, and phases evolution during mechanical alloying and spark plasma sintering of Cu-13.5Al-4Ni powders. We obtained alloyed powders with a structure composed of α(Cu), AlNi intermetallic compound and small amounts of elemental Al through the mechanical alloying technique. After spark plasma sintering at 900 °C, the microstructure consists of an AlNi compound distributed at the edge of α(Cu) grains. The crystallite sizes of both, α(Cu) and AlNi are in nanoscale order after 16 h of milling (9 and 6.5 nm respectively). After sintering at 900 °C (in Ar atmosphere, without holding time), the crystallite sizes increase to 46 nm for α(Cu) and to 40 nm for AlNi compound. Also, the Cu-13.5Al-4Ni compacts achieve a final density after sintering at 900 °C of around 80% from the theoretical density.