Alloy Powders Research Articles

Microstructure Evolution and Formation of Dual-Phase AlCoCrFeNiSi0.5 High-Entropy Alloy Powders by Mechanical Alloying

Microstructure Evolution and Formation of Dual-Phase AlCoCrFeNiSi0.5 High-Entropy Alloy Powders by Mechanical Alloying

Influence of Chemical and Phase Composition of Ni–P-Based Alloy Powders on the Corrosion Behavior in Various Environments

Influence of Chemical and Phase Composition of Ni–P-Based Alloy Powders on the Corrosion Behavior in Various Environments

Electrochemical determination of dopamine by poly (methyl orange) shape memory alloy modified carbon paste electrode

We have successfully prepared 50Ni-30Ti-20Hf shape memory alloy powders using a high-energy planetary ball mill for 20 h by wet milling. The fabricated shape memory alloy powders were characterized by X-ray diffraction (XRD), and scanning electron microscope (SEM) to investigate the phases present and the morphology of the powders respectively. The use of 50Ni-30Ti-20Hf (nitinol) shape memory alloy powders as electro-catalytic materials is a unique and new idea. We are the first researchers to use nitinol powders as dopamine (DA) electrochemical sensors. For better electrochemical oxidation and higher current response of DA, we have electro-polymerized the surface of nitinol-modified carbon paste electrode (MCPE) with methyl orange (MO). Using poly(MO)-NiTiHf-MCPE, we have determined the DA using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) respectively. The calculated active surface area for BCPE, NiTiHf-MCPE, and the poly(MO)-NiTiHf-MCPE were found to be 0.044, 0.089, and 0.098 cm2 respectively. The electro-polymerized nitinol MCPE not only increased the surface area but also increased the electron transfer kinetics. Our results confirmed the participation of 2 electrons and 2 protons in the electrochemical redox reaction.

Preparation of high-energy Al-Li alloy powders with enhanced compatibility and combustion performance by dense fluorosilane polymer composite coating

The superior combustion heat, lower ignition temperature, and enhanced combustion efficiency of aluminum–lithium (Al-Li) alloy powders have garnered significant research attention in relation to Al powders. However, the inadequate compatibility between Al-Li alloy powders (especially when Li > 3 wt%) and propellant components limits its application in the development of composite solid propellants. This study focuses on the surface-coating active Al-4.3Li (wt.%) alloy powder using a composite fluorosilane coupling agent to improve compatibility and combustion performance. A coating layer with a thickness of 30–40 nm was successfully formed on the surface of Al-4.3Li alloy powder through interactions involving Al-F, Al-O-Si, and Li-O-Si bonds, thereby achieving remarkable hydrophobicity. The heat release increased by 7.5 %, while the ignition delay time of the alloy powder decreased by nearly 200 ms, resulting in a significantly enhanced combustion performance in relation to that of the original Al-4.3Li alloy powder. Moreover, the modified Al-4.3Li alloy powder exhibited better compatibility, and no cracks or bubbles were observed in the cross-section of the propellant containing modified Al-4.3Li metal fuel. This study provides an effective approach for utilizing Al-Li alloy powders in solid propellants, which is of great significance for the development of high-energy propulsion systems.

Comparative study on manufacturing of EDM electrodes by laser sintering process

The abstract aims to investigate the comparative performance of Electrical Discharge Machining (EDM) and Selective Laser Sintering (SLS) with unconventional machining processes. Unconventional machining processes have gained significant attention due to their versatility and capability to fabricate intricate components with high precision. This study focuses on assessing the efficacy of EDM and SLS techniques in terms of data removal rate and relative wear volume. Electrical Discharge Machining (EDM) is a thermal erosion process that utilizes electrical discharges to remove material from a workpiece. In contrast, Selective Laser Sintering (SLS) is an additive manufacturing technique that employs a laser to selectively fuse powdered material, layer by layer, to build up a three-dimensional object. Both methods offer unique advantages in terms of precision, speed, and material compatibility. The performance evaluation of these techniques involves analyzing key parameters such as data removal rate, which measures the volume of material removed per unit time, and relative wear volume, which quantifies the wear on the tool or workpiece during the machining process. By comparing these metrics, insights into the efficiency and effectiveness of EDM and SLS can be gained, aiding manufacturers and researchers in selecting the most suitable method for specific applications. Through experimental investigations and data analysis, this study aims to provide valuable insights into the capabilities and limitations of EDM and SLS in unconventional machining processes. The findings will contribute to advancing the understanding of these techniques and optimizing their utilization in various industrial sectors, including aerospace, automotive, and biomedical engineering. The experimental analysis examines the impact of the Direct Metal Laser Sintering (DMLS) process parameter on sintering depth. The optimized parameters for AlSi10Mg alloy powder sintering were obtained using laser power at 162 W, scanning speed at 156 mm s−1, porosity at 20%, laser area size of 0.2 mm, and layer thickness of 1 mm.

Harmonizing microstructures and enhancing mechanical resilience: Novel powder metallurgy approach for Zn–Mg alloys

Zinc alloys are recognised for their excellent biocompatibility and favourable corrosion rates, making them suitable for bioabsorbable implants. However, their mechanical properties necessitate improvement to fulfil the rigorous requirements of biomedical applications. This research focuses on engineering pseudo-harmonic structures within zinc alloys through a comprehensive method combining mechanical alloying, spark plasma sintering, and hot extrusion techniques. This fabrication process results in a composite material characterised by a soft core surrounded by a continuous, three-dimensional, ultrafine-grained hard shell. The experiment involved blending pure zinc with Zn–1Mg alloy powder, leading to the formation of both ductile zinc and fine-grained Zn–1Mg regions. While the Mg2Zn11 intermetallic phase was found to enhance the alloy's mechanical strength, the presence of oxide shells adversely affected the material's properties. The elimination of these shells via hot extrusion markedly improved the alloy's tensile strength, reaching an average value of tensile strength of 333 ± 7 MPa. This study provides significant insights into the material engineering of zinc-based alloys for biodegradable implant applications, demonstrating a viable approach to optimising their mechanical performance.

Powder movement rules of laser powder bed fusion additive manufacturing aluminum alloy based on discrete element method

Laser Powder Bed Fusion (LPBF) is a promising metal additive manufacturing technology based on layer by layer powder spreading, and powder bed uniformity has a great influence on the forming quality. By Discrete Element Method and powder spreading experiment, the interaction and movement between powder were studied during powder spreading, including powder jamming, rebound, splash, eddy, and empty powder area. Additionally, five kinds of powder spreading schemes were explored, and the new process of one-way reciprocating with tri-splint blade was designed to change the motion state of powder spreading from “blade pushing powder” to “blade holding powder.” By increasing the distance between the blade and the working platform form 0 to 20 µm with the distance between the upper surface of the substrate and the working platform 50 µm, defects such as powder splash and empty powder decreased. And the uniform powder bed of aluminum alloy powder was achieved with the new process of one-way reciprocating with tri-splint blade structure.

Enhanced mechanical properties of dispersed carbide-strengthened CrFeNi-based medium entropy alloys prepared via powder metallurgy

In this study, a set of CrFeNi -based medium-entropy alloys (MEAs) with varying carbon contents were prepared by spark plasm sintering (SPS) using atomized alloy powders as raw material. The microstructures of powders and as-sintered alloys were characterized using ECCI and EBSD. The mechanical properties of as-sintered alloys were tested and the strengthening mechanical were discussed. The results showed that the microstructures of the CrFeNi gas atomized powder and sintered alloy were both single FCC phase in an equiaxed state. However, the matrix grains of powder with carbon addition were mostly dendritic, and few eutectic carbides could be observed between matrix grains. Compared with the CrFeNi MEA, the addition of 8 at. % C led to an increase in the yield strength and tensile strength from 395 MPa to 630 MPa–590 MPa and 990 MPa, respectively. Orowan strengthening and grain refinement resulting micro/nano carbides are responsible for the improvement in mechanical properties.

Microstructure and mechanical properties of Co31.5Cr7Fe30Ni31.5 high-entropy alloy powder produced by plasma rotating electrode process and its applications in additive manufacturing

Microstructure and mechanical properties of feedstock powders critically determine the quality of additive manufacturing (AM). The present study employs a plasma rotating electrode process (PREP) to produce non-equiatomic Co31.5Cr7Fe30Ni31.5 high-entropy alloy (HEA) powders and examines variations of their microstructure and mechanical properties with powder particle size in the range of 20–106 μm. It finds that the powders possess smooth surfaces, good sphericity, and equiaxed polycrystal grains under PREP electrode rod arc speed of 32000 r/min and main arc current of 760 A. A stable FCC structure is maintained regardless of the powder particle size. Moreover, the nano-hardness of the powders generally decreases with the increase of powder particle size except for that of 50–75 μm, which is positively correlated with the change of the grain size. The finest grain size is present for powders with particle sizes of 50–75 μm, which possess the highest average nano-hardness and reduced elastic modulus. Bulk alloys fabricated by cold spray (CS) and laser cladding (LC) AM maintain the FCC structure. The CSAM bulk alloy shows early brittle fracture due to the presence of pores and prior particle boundaries resulting from insufficient plastic deformation of the powder particles. The LCAM bulk alloy presents good tensile properties with the ultimate tensile strength (UTS) and elongation to failure being 481.2 MPa and 35.9%, respectively, which can be attributed to the good cohesion and grain characteristics. The present study shall provide the field of AM with useful information in the applications of non-equiatomic PREP HEA powders.

Determining technological parameters for obtaining ta15 titanium alloy blanks with improved mechanical characteristics using the electron-beam 3D printing method

The object of this study is the process of electron beam 3D printing of articles made of TA15 titanium alloy powder. Peculiarities of the structure and properties formation of alloy blanks, obtained by this method have been described. Influence of process parameters (electron beam power and geometric scanning parameters) on the characteristics of the material were considered. Step of displacement of the beam trajectory changed from 0.1 to 0.25 mm with an interval of 0.05 mm. Specific energy of the electron beam varied from 20 to 70 J/mm3 for every trajectory displacement step. The macrostructure was examined visually while the microstructure was studied by optical microscopy. Mechanical properties were determined by uniaxial tension and impact bending tests. It was established that depending on the 3D printing parameters the macrostructure of most samples is dense but with unfavorable parameters non-fusions or shrinkage porosity defects may form. The microstructure of the dendritic type has an α´+β lamellar-acicular morphology, its dispersity and shape of α´–phase areas vary depending on the process parameters. A scanning step of 0.2 mm and a beam energy of 40 J/mm3 allows obtaining a dispersed microstructure in which there are no non-fusions and shrinkage micropores. The value of the Rm is 27 %, and the R0.2 is 24 % higher than that of the alloy obtained by the conventional technology of electron beam melting. The A5 is 3.2 times higher. However, impact toughness of the sample with dendrite unfavorable orientation to the direction of load applying may be lower compared to conventional technology. The results could be used for devising commercial technology of high strength titanium alloys parts produced by 3D printing

Development and Evaluation of an AZ31 Magnesium Alloy and Eggshell Powder Composite for Orthopedic Surgical Implants

This research investigates the development and evaluation of a novel composite material composed of AZ31 magnesium alloy and eggshell powder, designed for use in surgical bone implants. The primary objective is to enhance the mechanical properties and biocompatibility of AZ31 by incorporating eggshell powder, which is known for its hardness and strength. The composite is fabricated using the stir casting technique, where the molten magnesium is mixed with finely ground eggshell powder to achieve uniform dispersion. The resulting samples are subjected to rigorous mechanical testing, including tensile and compressive strength evaluations, as well as hardness measurements. Additionally, the internal structure and particle distribution of the composite are analyzed using scanning electron microscopy and X-ray diffraction, respectively. This study aims to provide a comprehensive understanding of the material properties and structural characteristics of the composite, with a focus on its potential applications in orthopedic load-bearing implants and fixation devices, such as bone plates, joint replacements, screws, rods, dental implants, and cardiac stents. The findings are expected to contribute to the development of improved biomaterials for medical applications, leveraging the unique benefits of both magnesium alloy and eggshell powder.

Fabrication of AA3303 aluminum alloy by powder metallurgy techniques consolidated by sintering

This work analyzes the manufacture of the AA3303 aluminum alloy by powder metallurgy (PM) technique, using the uniaxial cold compaction and solid phase sintering route. The process will start with the AA3303 alloy powder manufactured by high-energy ball milling (HEBM), which will be compacted and then sintered, thus manufacturing a dense solid. This study aims to validate the PM manufacturing technique as an alternative in the production of the alloy studied. The manufactured alloy was characterized using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Vickers hardness (HV) tests. The characterization of the manufactured material showed marked porosity, low densification and an inhomogeneous microstructure, but acceptable hardness values were obtained for the alloy under study.

A novel process for the preparation of high-performance heat-resistant Al-Si-Fe alloy by powder metallurgy method

A novel method combining rotational extrusion with rapid solidification/powder metallurgy was developed to enhance the microstructure and properties of Al-Si-Fe alloys. This study conducted a comprehensive investigation into the phase composition, microstructure, and mechanical properties of the rotationally extruded Al-Si-Fe alloy. Experimental results confirmed the presence of α-Al, β-Si, α-Al8Fe2Si, Al2FeSi, and Al2O3 phases within the alloy. The rotary extrusion technique significantly increased the density and reduced the porosity of the Al-Si-Fe alloy. The rotationally extruded alloy demonstrated considerably higher maximum microhardness and tensile strength (170 HV and 487 MPa, respectively) compared to the alloy produced by single forward extrusion. This study highlights how the superposition of deformation not only modifies the structure but also breaks the initial boundaries of the alloy powder particles, enhancing metallurgical bonding during subsequent sintering.

Improving interfacial magnetoelastic effect and complex permeability of FeSiAl alloy powders for broadband decimeter-wave absorption via Cr doping

This study showcases the interfacial magnetoelastic effect observed in flaky FeSiAl alloy powder absorbents, aimed at enhancing permeability in the decimeter-wave band for better absorption performance through Cr doping via wet ball-milling and subsequent annealing processes. The wet ball milling process facilitates the formation of a lamellar structure by inducing slip along shear stress in DO3 and α-Fe nanocrystals. During annealing, the introduced Cr element partially impedes the transition from the α-Fe phase to the DO3 phase, thereby amplifying the difference in magnetostrictive coefficients between these phases. Consequently, the flaky FeSiAlCr powders exhibit notably increased initial permeability and resonance frequency, particularly around 3 GHz, owing to domain rotation in the DO3 phase. In comparison to previously reported counterparts, the composite derived from these powders demonstrates a significant enhancement in the real part of effective permeability by approximately 66 %, alongside a 17 % reduction in density. Consequently, this composite exhibits a lowered reflection loss of below −5 dB within the frequency range of 0.7–3 GHz, reaching a minimum of −11 dB at 1.57 GHz, specifically with a thickness of 1.6 mm. These findings present an effective strategy for enhancing the magnetic permeability of alloy powders. The resultant microwave absorbing materials hold promising applications in stealth technology and wireless communication electronics.

Material extrusion of high-density SiCp/7075Al composite via a high nitrogen-flowing assisted sintering

Material extrusion additive manufacturing of particle-reinforced metal matrix composite (MMC) attracts attention due to the features of uniformly sintered microstructure, easy-to-handle and low cost. However, 3D Al-MMC suffers from poor sinterability due to the stable alumina layer on alloy powder, and difficulty in removing of binders at low temperature. Here, we propose a high nitrogen-flow sintering approach for the thermal debinding and sintering of as-printed SiC particle-reinforced 7075Al (SiCp/7075Al) MMC, without using cumbersome high-vacuum system or pressure-assisted densification. Microcrystalline wax-based granular feedstock was developed based on contact angle testing experiment, which shows typical shear-thinning behavior and satisfactory printing performance. Roles of printing parameters and nitrogen flow rate in the microstructure, phases and mechanical properties of SiCp/7075Al MMC are investigated. Nitrogen flow rate of 2–2.5 L/min accelerates the breaking of oxide film, with the precipitation of intergranular MgAl2O4, Mg2Si phases, and intragranular Al2Cu phases. 3D SiCp/7075Al MMC with a high relative density of 97% and tensile strength of 308 MPa after heat treatment (HT) was achieved based on optimized printing parameters. The availability of high dense structure, combined with controlled microstructure, low-energy demand and low cost, provides a facile route for the application of 3D Al-MMC by material extrusion.

Enhancing Microstructural Characteristics and Mechanical Properties of Ti-Al-Dy Alloy through Ball Milling and SPS Consolidation

In this study, pure Ti, Al, Dy powders were ball-milled with zirconia balls in argon atmosphere for 3 h at 800 rpm, producing a Ti- 6 wt.% Al- 4 wt.% Dy alloy powder. The alloy powder was consolidated by SPS technique at 1373 K for 15 min under 50 MPa pressure in vacuum. The sintered body had approximately 99% in density and 6 μm in grain size. XRD and TEM revealed the presence of the second phases such as Ti3Al, Al3Dy and Ti4Al20Dy phases, and their sizes were approximately 50 nm. Microhardness was approximately 960 Hv at room temperature, which decreased as temperature increased. However, there remained the micro-hardness significantly higher compared to the commercial Ti-6Al-4V alloy. After hardness test at 1173 K, XRD analysis did not show any difference in peaks, while the grain size and second phases size increased by ~4 μm and ~2 nm, respectively.

Hydrogen Reduction Behavior and Microstructure Characteristics of WO3-NiO-CuO Powder Mixture

The characteristics and hydrogen reduction behavior of W-0.8 wt% Ni-0.4 wt% Cu powder synthesized from WO3-NiOCuO composite powder have been investigated. The metal oxide powder mixtures were prepared using a ball milling process. XRD analysis and HR-TEM revealed that the oxide powders are changed to W and CuNi alloy powders with an average particle size of about 100 nm by hydrogen reduction. To understand the reduction behavior of oxide powders, TG analysis was performed, and the reduction kinetics was evaluated by the amount of peak shift with heating rates. The activation energies for the reduction of WO3-NiO-CuO, estimated by the slope of the Kissinger plot, were measured as 60.6-114.4 kJ/mol depending on reduction steps.

Microstructural and photocatalytic properties of nanostructured near-β Ti-Nb-Zr alloy for total hip prosthesis use

With its unique corrosion resistance, light weight, mechanical strength, and biocompatibility, TNZ is a versatile metal alloy that is used in the aerospace and medical industries. The current study aims to investigate the effect of milling time (2, 12, 24, and 36 h) on the nanostructured ternary alloy Ti-25Nb-25Zr (TNZ) prepared by high energy ball milling, a process involving the use of a high-energy ball mill to mix and grind the alloy powders, on its structural, physical, and photocatalytic characterizations. The alloys' characteristics, such as morphology, structural properties, relative density/porosity, surface roughness, hardness, and Young's modulus, were evaluated using SEM, XRD, surface profilometer, and microdurometer, respectively. The photocatalytic characterization was conducted by measuring their absorbance as a function of time using a spectrophotometer of visible and ultraviolet light in the wavelength range of 250–650 nm. Results showed that the crystallite and mean pore size reduced with increasing milling time, with the smallest values of 25 nm and 34 μm, respectively, after 36 h. This indicates that longer milling times result in a more compact and uniform structure, which could enhance the mechanical properties of the alloy. Structural characterization shows that the amount of the β-Ti phase increased with increasing milling time, resulting in the spherical morphology and texturing of the synthesized alloys. The milled alloys' structural evolution and morphological changes were sensitive to their milling times. Also, the relative density, Young's modulus, and hardness increased, reaching values of 89 %, 105 GPa, and 352 HV, respectively, due to grain size decreasing with increasing milling time. This suggests that longer milling times lead to a denser and harder alloy, which could be beneficial for its use in total hip prostheses. The photocatalytical characterization demonstrated that the degradation of orange II (OII) increased with increasing milling time. The Ti-25Nb-25Zr catalyst gave the best degree of degradation, which meant that the decolorization process could be operated rapidly and at a relatively low cost without UV irradiation.

The effects of adding Si3N4 as a nitrogen source on the properties of Ni-Free Co-28Cr-6Mo-xN alloy powders developed by mechanical alloying

Co-Cr-Mo alloys, which also contain Ni, are often used as materials for implants in orthopedic surgery due to their excellent mechanical properties and resistance to corrosion. However, when these alloys are implanted into the body, they can release nickel ions into the host tissues, which can pose health risks over time. To address this issue, nitrogen can be substituted for nickel. This study involves the synthesis of cobalt-based alloy powders, following the chemical composition specified by ASTM F1537, using different percentages of silicon nitride as a nitrogen source via the mechanical alloying method in an argon atmosphere. The effects of increasing silicon nitride content on the particle morphology, particle size, phase transformations, microstructure, and hardness of the synthesized powders were investigated using XRD, SEM, TEM, and microhardness tests. The results obtained from the X-ray diffraction analysis indicate that the alloying process was conducted effectively. It was observed that the silicon nitride underwent decomposition, and a portion of its nitrogen reacted with chromium to form the chromium nitride phase. Additionally, it was observed that an increase in the silicon nitride content resulted in a decrease in crystallite size and an increase in lattice strain. Adding silicon nitride in varying percentages resulted in crystal sizes within the nanometer range. The SEM results indicated that the size of powder particles decreased with an increase in the content of silicon nitride, and there was a more uniform distribution of particle sizes, with less variation in size. The TEM images showed that all percentages of silicon nitride resulted in a fine-grained polycrystalline phase, where the size of the crystallites decreased with an increase in the amount of silicon nitride. The corresponding SAED patterns supported this observation. Moreover, the hardness of the material increased as the silicon nitride content increased.

Synthesis and characterization of multi-walled carbon nanotube-reinforced Ti–Mg alloy prepared by mechanical alloying and microwave sintering

Titanium-magnesium (Ti–Mg) alloy is a widely accepted bimetallic material suitable for biomedical applications. However, reduced wear and corrosion resistance, low strength and hardness, and stress shielding effect limit their widespread applications. Reinforcing multi-walled carbon nanotubes (MWCNTs) possessing low density, high modulus, and improved mechanical properties overcome the shortcomings of Ti–Mg alloy. In the present work, nanostructured Ti–Mg alloy was synthesized at room temperature and simultaneously reinforced with MWCNTs. The high energetic ball milling process (HEBM) has been successfully utilized to mechanically alloy Ti with Mg at room temperature by decreasing the grain size to the nanoscale and reinforcing the alloy with MWCNTs. The synthesized nanostructured powder size was 25 nm. Characterization results have shown the emergence of new phases like Ti4C4 and Mg2C3 as a result of mechanical alloying (MA). The reinforced alloy powder was consolidated by cold compaction and followed by microwave sintering. The consolidated sample crystallite size attained was 72 nm and then characterized by Nanoindentation, XRD, and SEM. XRD results show intermetallic compounds Mg2C3 and TiC in bulk samples. SADP TEM confirmed the retention of Nano and partial amorphous structures in the consolidated samples. The nanoindentation test revealed the hardness and elastic modulus values 0.93 GPa and 28.12 GPa, respectively, equivalent to CpTi and its associated alloys. The results are prevalent in those alloys used in biomedical applications produced by conventional melting and casting techniques and can be a potential biomaterial.