Mechanical Alloying Method Research Articles

Laser Powder Bed Fusion Applied to a New Biodegradable Mg-Zn-Zr-Ca Alloy.

The aim of the present paper is to apply the laser powder bed fusion process to a new biodegradable Mg-Zn-Zr-Ca alloy powder prepared via a mechanical alloying method from powder pure components. This additive manufacturing method is expected to allow for the obtaining of high biomechanical and biochemical performance. Various processing parameters for laser powder bed fusion are tested, with a special focus on laser energy density—E [J/mm3]—which is calculated for all experiment variants, and which represents an important processing parameter, dependent upon all the rest. The goal of all the trials is to find the most efficient schema for the production of small biodegradable parts for the medical domain, meaning the selection of optimal processing parameters. An important observation is that the most robust and homogeneous samples without cracks are obtained for lower values of the E, around 100 J/mm3. Thus, the most performant samples are analyzed by scanning electron microscopy, X-ray diffraction and by compression mechanical test.

Microstructural and Mechanical Properties of AA7075 Al Alloys Produced via Mechanical Alloying Process

In this study, it is aimed to produce AA7075 materials by mechanical alloying and sintering methods. Besides, the main purpose of this study is to investigate the effect of different ball milling times on the powder and sintered samples. The milled powders and sintered samples were thoroughly investigated by different characterization techniques. Initially, AA7075 alloy powders were milled by planetary high-energy ball milling device with different milling times. While the initial particle size of commercial grade AA7075 powders were calculated 46 µm, the average particle size of the 8 hours milled powders measured as 22 μm. The effect of different milling times (i.e., 0.5, 1, 2, 4 and 8 hours) on the morphological properties of AA7075 milled powders were investigated by scanning electron microscopy (SEM) and particle size analyses. In addition, X-ray powder diffractometry (XRD) was performed to observe the differences in the crystallographic properties of the milled powders. After the powder preparation and characterization stages, in order to determine the effect of the different phases of milling process on the mechanical properties of the produced AA 7075 samples, these milled powders were consolidated via cold press followed by sintering process. According to experimental outcomes, it was observed that when the milling time reached the final stage (8 hours), the relative density of bulk AA7075 decreased by 7%, in contrast the hardness increased by 130% as compared to pure AA7075 sample fabricated by same producing history.

High‐temperature corrosion of mechanically alloyed Cr–AlSi12 composite coatings on Ti–6Al–4V alloy substrate

AbstractIn the present work, the Cr–AlSi12 composite coatings were successfully synthesized on the Ti–6Al–4V alloy substrate by using the mechanical alloying method. The effects of raw Cr particle size, milling duration, and annealing treatment on the preparation of the coatings were investigated. The as‐prepared coatings consisted of the inner coating layer with coarse Cr particles and the outer coating layer with refined and highly homogenized structure. The annealing treatment could promote element diffusion and alloying; it was favorable to the densification and oxidation resistance of the coatings. There is a highly densified alloyed layer in the outer coating. The annealed coating showed excellent friction and wear resistance. After the oxidation process, the annealed coating showed the best high‐temperature oxidation resistance. The oxidized annealed coating exhibited four layers, which included the thin Al2O3 oxide film, the homogenized alloyed layer, the composite layer consisted of Al2O3 and coarse Cr particles surrounded by alloyed layer, and the Al3Ti diffusion layer. This was favorable to the improvement of high‐temperature oxidation resistance. The oxidation process of the annealed coating was elaborated.

Fabrication and Characterization of Mullite Reinforced CeO2 Added ZrO2 Ceramics

In this study, mullite (3Al2O3.2SiO2) and 10 mol % ceria added zirconia (10 mol % CeO2 - 90 mol % ZrO2) ceramic powders were synthesized by conventional ceramic production processing route. The mixtures were prepared by mechanical alloying method in acetone environment with zirconia ball mill. Mullite and ceria added zirconia ceramic powders were synthesized in air at 1600 oC for 3 h and 1300 oC for 2 h, respectively. Then, the ceramic phases formed were made ready to form ceramic - ceramic composites by crushing, grinding and sieving processes. Then 0 and 10% by weight mullite added ceria doped zirconia mixtures were prepared by powder metallurgy method. The prepared mixtures were wet milled with zirconia ball mill for 24 h and sieved. After drying, the powders were compacted by uniaxial pressing at 200 MPa. The green compacts were sintered at 1500-1600 oC for 1-5 h in air conditions using a heating rate of 5 oC min-1 in a high temperature furnace. Then, microstructure (SEM), phase analysis (XRD), mechanical (hardness, 3-point bending and wear) and physical properties (% shrinkage, water absorption, porosity and density) tests were performed on the ceramic composites. In this study, whether there is a phase change in the ZrO2 - CeO2 mixture at high sintering temperatures and the effect of mullite additive on the properties of this mixture was investigated.

Modernization of Electrode Composite Material Based on Copper Powder for Electrical Discharge Machining of High-Strength Alloys

As a result of implemented modernization of known electrode composite material based on Cu-3% wt BN copper powder successfully used for electrical discharge machining of high-strength alloys, composite material (Cu - 3% wt BN) – 0.5 % wt Al – 0.25 % wt in the form of high-density long thin-wall plates for operations of electrical discharge cutting and piercing of hard-to-machine materials was obtained. The new material was obtained with the use of the method of reactionary mechanical alloying of initial powder components in the attritor. Tool electrodes made of the new material during electrical discharge piercing of rectangular holes in titanium alloy sheets ensure a 1.6 times higher machining rate comparing to tool electrodes made of the Cu-3% wt BN prototype material. After replacement of rolled copper in tool electrodes with the new composite material the machining rate will increase 4.1 times. The tool electrodes made of this material have significantly lower electrical discharge wear comparing to the wear of tool electrodes made of the prototype material and rolled copper.

Optimization of Dispersion-Strengthened Material Based on Copper Powder for Valve Guides of Internal Combustion Engines

The given study is dedicated to optimization of dispersion-strengthened material based on copper powder of the Cu-Al-C-O system used for valve guides of internal combustion engines. The developed material containing 3 % wt aluminum, 0.6 % wt carbon and not more than 0.02 % wt oxygen has the recrystallization temperature of 1000оС and exhibits higher tribotechnical properties comparing to the prototype. In particular, the wear out intensity of the developed material is 2.5 times lower. The material production technology is based on the method of reactionary mechanical alloying in the attritor and powder and granular metallurgy technologies.

Wear behaviors at different temperatures of ZrO2 reinforced A356 matrix composites produced by mechanical alloying method

PurposeThe purpose of this study, the tribological behaviors at different temperatures of aluminium matrix composites (AMCs) with different amounts of ZrO2 added were investigated.Design/methodology/approachAluminium graphite (A356/2 wt% graphite (solid lubricant)) composite powders prepared by adding four different amounts (3 wt%, 6 wt%, 9 wt% and 12 wt%) of Zirconia (ZrO2) to the matrix were mechanically alloyed for 4 h. Wear tests were conducted at five different temperatures (20 °C, 100 °C, 180 °C, 260 °C and 340 °C) and for three different sliding distances (53 m, 72 m and 94 m) on the pin-on-disc type wear tester.FindingsResults of the study showed that the highest hardness and density value were measured for 12% ZrO2 added AMC material. Wear test results showed that weight loss increases with increasing temperature; weight loss decreases at all temperatures with the increasing amount of reinforcement in the matrix.Originality/valueIn this paper, the tribological properties of aluminium matrix composites produced by the mechanical alloying method by adding different amounts of ZrO2 were determined by simulating the tribological properties at different loads and temperatures.

Microstructure and morphology related electrical characterization and dielectric relaxation studies of nanocrystalline Sb2Te3 synthesized by mechanical alloying

This article explores a rapid and facile mechanical alloying method for synthesizing nanocrystalline Sb2Te3 at room temperatures with the least number of ingredients under an inert atmosphere. XRD, FESEM, and TEM have characterized the structure and microstructure. The rhombohedral Sb2Te3 phase formation without any impurity has been ascertained after 3 h of milling. A minimal size-dependent band gap is revealed from the FTIR spectra. The ionic conductivities measured in the temperature range 300–473 K increases with rising temperature, confirming the semi-metallic character of samples. The impedance spectra analysis reveals the electrical relaxation process and temperature-dependent transport properties. The non–Debye type behavior is confirmed from the Cole-Cole plot. The frequency-dependent ac conductivity obeys the universal Jonscher power law, and a small polaron transaction is used to explain the temperature dependence of the frequency exponent. A reduced value of dielectric loss factor at higher frequencies makes the material applicable in higher frequencies.

Nanostructure formation and thermal stability of nanophase materials prepared by mechanical means

Abstract Mechanical attrition, mechanical alloying and other methods of extreme plastic deformation (high pressure torsion, equal channel angular pressing) have been developed as versatile alternatives to other physical and chemical processing routes in preparing nanophase materials. Here several examples are discussed including the deformation-induced nanophase formation in powder particles, in thin-foil sandwich structures and at the surface of alloys exposed to friction-induced wear, leading to the formation of nanocrystals and, in some cases, amorphous nanostructures. This opens exciting perspectives in preparing nanostructured materials with a number of different interface types in terms of structure (crystalline/crystalline, crystalline/amorphous) as well as atomic bond (metal/metal, metal/semiconductor, metal/ ceramic etc.). It is expected that the study of nanostructure formation by mechanical means in the future not only opens new processing routes for a variety of advanced nanophase materials but also improves the understanding of technologically relevant deformation processes on a nanoscopic level.

Effect of Additive Elements (x = Cr, Mn, Zn, Sn) on the Phase Evolution and Thermodynamic Complexity of AlCuSiFe-x High Entropy Alloys Fabricated via Powder Metallurgy

In this study, equimolar AlCuSiFe-x (x = Cr, Mn, Zn, Sn) HEAs were fabricated by mechanical alloying (MA) and spark plasma sintering methods (SPS). The MA was performed for 45 h followed by densification of powder compacts at 650 °C. The results revealed the formation of dual face-centered cubic (FCC) and body-centered cubic (BCC) structures in AlCuSiFe-x (x = Zn, Sn) while a single BCC solid solution was noticed in AlCuSiFe-x (x = Cr, Mn). After SPS treatment, AlCuSiFeSn alloy contained FCC with CuxSny while AlCuSiFe–Zn changed to FCC + BCC structure. Similarly, AlCuSiFeCr and AlCuSiFeMn showed the formation of BCC + FCC with additional σ- and µ-phases in the HEA matrix. The calculated thermodynamic parameters of HEAs also supported the formation of different solid-solution phases in each of the above HEAs. It was found that HEAs with the additive elements Sn and Zn tend to have major FCC phases, while those with Cr and Mn give rise to major BCC with brittle σ- and µ-phase, which further improves their mechanical strength. Graphic Abstract

Enhanced wearing resistance of carbide reinforced FeCoNiCrMn high entropy alloy prepared by mechanical alloying and spark plasma sintering

Aiming to improve the wearing resistance of high entropy alloys (HEAs), this work prepared carbide reinforced FeCoNiCrMn HEA composites using mechanical alloying (MA) and spark plasma sintering (SPS) methods. The multiple carbides were introduced into the HEAs in two ways using in situ hydrocarbon additives in the MA process (HECin) and ex situ carbide additives (HECex) as carbon resources, respectively. The HECin consisted of HEA solid solution and embedded carbides of M23C6 and M7C3, leading to yield strength (YS) 1756 MPa and maximum compressive strain (MCS) 10.28%, ~14.5% stronger than the reported HEAs prepared via MA and SPS processing. The HECex introduced additional 5 wt% TaC and TiC, leading to YS 1760 MPa and MCS 7.85%. Compared with the HECin, the HECex increased hardness by ~40% (from 7.44 GPa to 9.47 GPa), but decreased friction coefficients by ~18% (from 0.32 to 0.26). The microstructure analysis of worn surface show that the HECin had adhesive wearing and slight oxidation wearing while the HECex had mainly oxidation wearing with slight adhesive wearing and fatigue wearing. This work demonstrated that the carbide reinforced HEA has superior wearing resistance properties compared with the pristine HEA and can be adopted as an effective hard coating materials.

The effect of the amount of Y2O3 doped to the MA6000 alloy produced by mechanical alloying method on wear behavior

This paper investigated the wear performances of Y2O3 doped MA6000 (Ni-Cr-Al) alloy produced by mechanical alloying (MA). Produced, all powders were pre-formed by cold pressing and sintered in a vacuum environment. Sintered MA6000- X% Y2O3 superalloys were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) analysis, density, and hardness measurements. Wear tests of Y2O3 added MA6000 alloys were carried out in a block-on-ring type wear device. In the wear tests, the sliding speed of 1 ms-1 at room temperature (RT) was performed under five different sliding distances (200-1000 m) and three different loads (5 N, 10 N, and 15 N). As a result of the studies, it was determined that the MA-ed MA6000 superalloy powders were homogeneous and flake shape. With the increase amount of Y2O3, hardness of these superalloys increased from 267 to 431 Hv, but the density slightly decreased. Different intermetallic/carbur phases such as Ni3Al and MoC were observed in all compositions. Wear tests show that weight loss and wear rate decreased, and friction coefficient (?) increased with the increasing amount of Y2O3 additive. Besides, it was determined that as the applied load increased in the wear test, the weight loss increased, but the wear rate and friction coefficient (?) decreased.

Influence of structure phase transition on the thermoelectric properties of Cu2Se1-x Te x liquid-like compounds.

Copper chalcogenide Cu2(Se,Te) compounds are well known as typical p-type thermoelectric materials with a figure of merit (ZT) that can be optimized by the ratio of Se : Te. Here, by using the mechanical alloying and solid-state reaction methods, Te was substituted into Se sites within Cu2Se as the formula Cu2Se1−xTex (x = 0.1, 0.2, 0.25, and 0.3). The observed changes in structural phase, grain morphologies, and grain size were recorded by XRD and FE-SEM imaging with the appearance of the secondary phase of Cu2Te, with a Te content of x = 0.25. The layered structure morphology was observed more clearly at the high Te content. The electrical conductivity was greatly increased with enriched Te content while the maximum Seebeck coefficient was obtained in the Cu2Se0.75Te0.25 sample. Accordingly, a power factor value of up to 9.84 μW cm−1 K−2 at 773 K was achieved. The appearance of a Cu2Te phase with a Te content of 0.25 created a structural phase transition which results in a ZT value of 1.35 at 773 K in the Cu2Se0.75Te0.25 sample.

Microstructure, optical and electrical characterizations of Bi-incorporated Sb2Te3 thermoelectric compound synthesized by mechanical alloying: A comparative study with undoped Sb2Te3

Bismuth incorporated antimony telluride has been synthesized within 3 h via the facile mechanical alloying method at room temperature. The rhombohedral crystal structure, microstructure (i.e, crystallite size, lattice strain etc.), and morphology of the sample have been revealed from Rietveld's refined XRD patterns and FESEM images. FTIR study confirms that the sample is a narrow bandgap semiconductor. The detailed study of impedance spectra, ac conductivity reveals the frequency and temperature-activated non-Debye type relaxation process of this semiconducting sample. The lower dielectric loss value at high frequencies shows the better applicability of the material in the high-frequency zone of optoelectronics. All the properties are compared with the previously reported undoped 3 h milled Sb2Te3 sample.

Theoretical and technological aspects of production mechani‑cally alloyed powders for the production of coatings and products by additive methods

The established regularities of the formation of powders based on iron and nickel, obtained by the method of mechanical alloying and intended for the deposition of thermal spraying coatings, as well as the manufacture of products by layer‑by‑layer synthesis. The structure, phase composition and properties of materials are investigated. Powders consist of particles with a size of 20–70 microns, differ in the submicrocrystalline type structures, and nonequilibrium phase composition. Thermal spray coatings made of them have a set of properties that significantly exceed the properties of coatings made of commercially available materials. The diameter of the grains of the material obtained by the SLМ method from the synthesized powder is 1.5–2.0 times smaller than that produced from the powder of 316L steel, and the heat resistance is higher.

The microstructure, mechanical-thermal properties and softening resistance of Y4Al2O9 dispersion-strengthened Cu alloy

Oxide dispersion-strengthened copper (ODS-Cu) alloys with yttrium oxide nanoparticles are promising heat sink materials in fusion reactor due to their high strength, thermal conductivity and thermodynamic stability. The particle size and number density of oxide nanoparticles can be improved via addition of microalloying element. In this study, the atomized Cu-Y alloy, Al and Cu2O were used as the Y source, the microalloying element and the oxidant material, respectively, to fabricate ODS-Cu alloy by mechanical alloying method. After spark plasma sintering and annealing, a ODS-Cu alloy with a microstructure containing Y4Al2O9 nanoparticles homogeneously distributed in Cu(Al) solid solution matrix was successfully fabricated. It is found that a crystallographic orientation relationship of (31¯2)Y4Al2O9∥(11¯1)Cu(Al) was formed between Y4Al2O9 nanoparticles and Cu(Al) matrix and the lattice mismatch was 0.337%. The small lattice mismatch reduced the nucleation barrier for Y4Al2O9 nanoparticles so a mean particle size of 4.8 nm and a number density of 2.16×1024 m−3 were obtained in the alloy. Consequently, the microhardness was enhanced via Hall-Petch strengthening, dislocation strengthening and dispersion strengthening. The softening temperature of ODS-Cu alloy was improved to higher than 1000 °C due to the thermodynamic stability and the pinning effect of Y4Al2O9 nanoparticles. In addition, the thermal conductivity of Cu-1Y-9Al-0.3Cu2O alloy is close to other copper alloys as the volume fraction of Y4Al2O9 nanoparticles is limited. Cu-1Y-9Al-0.3Cu2O alloy provides a good overall performance, which may be used as heat sink materials under severe conditions.

Thermoelectric Ag2Se: Imperfection, Homogeneity, and Reproducibility.

Ag2Se is a narrow band gap n-type semiconductor with high carrier mobility and low lattice thermal conductivity. It has high thermoelectric performance near room temperature. However, there is a noticeable data discrepancy for thermoelectric performance in the reported literature studies, which greatly hinders the rational understanding and potential application of this material. In this work, we comprehensively studied the homogeneity, reproducibility, and thermal stability of bulk Ag2Se prepared by melting and mechanical alloying methods followed by spark plasma sintering. By virtue of the atom probe topology technique, we revealed nanosized Ag- or Se-rich precipitates and micropores with Se-aggregated interfaces that have not been detected previously. The samples prepared by melting and spark plasma sintering exhibit the best homogeneity and repeatability in thermoelectric properties despite abundant nanoprecipitates. Moreover, the thermoelectric performance of Ag2Se is greatly improved by introducing a slight amount of excess selenium. The average zT can steadily reach 0.8-0.9 in the range of 300-380 K, which is among the highest values reported for Ag2Se-based materials. This work will rationalize the evaluation of the thermoelectric performance of Ag2Se.

Microstructural and mechanical properties of NiCoCrAlSi high entropy alloy fabricated by mechanical alloying and spark plasma sintering

In this study, the microstructural and mechanical properties of NiCoCrAlSi high entropy alloy (HEA) fabricated by mechanical alloying and spark plasma sintering (SPS) method was studied. Initially, the starting powders with the composition of Ni28Co26Cr26Al10Si10 were subjected to mechanical milling at different times of 5, 10, 15, 20 and 40 h. The 40 h milled powder was then sintered by SPS method at 1170 °C. The microstructural characterization, phase analysis and mechanical properties of this sample were evaluated by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Rietveld analysis and tensile test. XRD results showed that by increasing the milling time the size of crystallites reduced and lattice strain increased. In addition, formation of FCC1 (F1) phase at final stages of mechanical alloying was observed. However, the peak of some of the remaining elements was still observed after 40 h of milling. After sintering, formation of FCC2 (F2) phase alongside F1 was observed. According to quantitative analysis, F1 phase with fraction of 89.3 wt% and F2 phase with fraction of 10.7 wt% is formed after SPS process. For this sample, a tensile strength of 1365 ± 141 MPa was obtained.

Synthesis and Characterization of Ba0.6Sr0.4Fe12O19/LaMnO3 Composites as Microwave Absorbers

The synthesis and characterization of Ba0.6Sr0.4Fe12O19/LaMnO3 composite material has been successfully carried out by mechanical alloying method using high energy milling. Crystal structure and surface morphology were characterized using x-ray diffraction and scanning electron microscopy. While the value of magnetization and the ability to absorb microwaves, vibrating sample magnetization and vector network analyzing were used, respectively. With variations in weight, does not change the crystal structure. The Ba0.6Sr0.4Fe12O19phase has a hexagonal structure and the LaMnO3 phase has an orthorhombic structure. Surface morphology has a heterogeneous size in the range of 200-450 nm with the form of platelets. The composite material Ba0.6Sr0.4Fe12O19/LaMnO3 is a hard-soft magnetic material with a magnetic saturation of Ms ~ 46.83 emu/g, Mr ~ 28.8 emu/g, and a coercive field of Hc ~ 3.88 kOe. The minimum reflection loss value is – 13.0 dB at 11.2 GHz frequency and 1.52 GHz bandwidth.

Investigation on magnetic properties of mechanically alloyed τ-MnAlC with Fe addition

The influence of Fe addition on thermal stability, crystallography, and magnetic properties of τ-Mn51Al47C2 was investigated. Alloys with composition Mn51-xFexAl47C2 (x = 0, 0.5, 1, 2, and 4) were synthesized by mechanical alloying method. High purity of τ-Mn(Fe)AlC up to 98% could be obtained after 10 h of milling, then annealed at 1050 °C for 1 h, and followed by an aging process at appropriate temperatures from 515 to 540 °C for 50 min. It was found that the thermal stability of both ε and τ phases was enhanced by the addition of Fe up to 4 at.% into MnAlC alloy through a shifting of ε-to-τ transformation temperature to high temperature region and a reduction in c/a ratio of Fe doped τ-MnAlC compared to iron free τ-MnAlC. While the magnetization and Curie temperature of Fe doped τ-MnAlC showed a reduction compared to iron free τ-Mn51Al47C2, coercivity seems not to be significantly affected. Ab initio calculation showed a lower magnetic moment of Fe (μFe = 1.77 μB) compared to Mn (μMn_average = 2.36 μB) in τ-Mn(Fe)AlC when Fe substituted Mn position at 1a site.