High-energy Mechanical Alloying Research Articles

Temperature-dependent structural and magnetic properties of mechanically alloyed Ni80Co17Mo3powder mixture

Nanostructured materials containing nickel improve the effectiveness of several applications. This study examines the preparation and characterization of nanostructured Ni80Co17Mo3 alloy powders using high-energy mechanical alloying and subsequent annealing. A 72h milling process used pure elemental powders to synthesise nanocrystalline FCC-NiCo(Mo) solid solution. The milled powders were then subjected to annealing at different temperatures:300°C, 500°C, and 750°C. X-ray diffraction, scanning electron microscopy coupled with energy-dispersive spectroscopy, and vibrating sample magnetometry indicated significant changes in the powdered alloy properties. The particles growth occurred as the annealing temperature increased, while the microstrain decreased significantly; 14.30±0.07nm up to 56.30±0.28nm and 0.680±0.003% up to 0.180±0.001%, at 25°C and 750°C respectively. SEM analysis revealed differences in particle size and shape as milling progressed. Surprisingly, the milled powdered alloy displayed improved magnetic properties, manifesting significant magnetic susceptibility and enhanced saturation magnetisation, remanent magnetisation, and coercivity within the temperature range of 300°C to 750°C. These findings indicate the development of a consistent and structured state, accompanied by significant crystal growth due to the annealing temperature. This study highlights the great importance of high-energy mechanical milling and subsequent annealing to tune / tailor the characteristics and subsequently investigate the potential utilization of nanostructured Ni-based alloys.

Mechanical alloying of AlCoCrFe and AlCoCrFeNi: Design and experimental evaluation of medium- and high-entropy alloy particles for cold spraying

The manufacturability of equiatomic high-entropy alloy (HEA) particles with single- and dual-phase crystal structures using the high-energy mechanical alloying (HE-MA) method was explored in this study. Following a material design-of-experiment (DoE) curriculum, particles were synthesized in a planetary mill. Milling times varied while operating under two distinct HE-MA manufacturing regimes: the conventional approach (simultaneous milling of constituent elements) and the sequential method (progressive milling with the introduction of elements in a specific order). Within the conventional regime, equiatomic AlCoCrFe and AlCoCrFeNi blends were milled, focusing on the influence of incorporating nickel (Ni) as a transient element into the base composition. This led to an equivalent particle size distribution ranging from 5 to 100 μm. Notably, the presence of Ni resulted in an increased fraction of the face-centered cubic (FCC) phase, coupled with a simultaneous reduction in grain and crystallite sizes, thereby enhancing the overall material strength. This knowledge was applied to the design and synthesis of a target equiatomic FeNiCoCrAl HEA system. In this context, individual elements were added to the starting/milled Fe + Ni alloy at four-hour intervals, in line with the sequential milling regimen. The results showed an interesting evolution: the conventionally milled AlCoCrFeNi particles exhibited a dual-phase body-centered cubic (BCC) and FCC structure, with a composition of 55% BCC and 45% FCC phase fractions, while the sequentially milled FeNiCoCrAl particles demonstrated a single-phase BCC structure after 24 h of milling.

Structural, microstructural, and magnetic properties of nanocrystalline-amorphous Fe–Co–Ta–B alloy processed by high-energy mechanical alloying

A nanocrystalline Fe(Co) phase dispersed within an amorphous matrix was achieved after milling of Fe31Co31B30Ta8 powder mixtures up to 200 h by using a high-energy ball mill. The transformations occurring in the powders during milling were studied with the use of X-ray diffraction and scanning electron microscopy techniques. The transformation of the phase depends upon the milling time. With the increase of milling time, various nanostructured phases such as Fe(Co), Co2Ta, Co(Ta,B), fcc-Co, Fe-type borides, and amorphous phase were identified. Magnetic properties were also investigated and correlated with microstructural changes. By increasing milling time, irregular variation of saturation magnetization is identified in relation to the change in the composition of the system. Also, the gradual decrease in grain size to a few nanometers resulted in an increase in coercivity while increasing the milling time up to 200 h. The existence of non-magnetic Ta and B atoms in the neighboring Fe and Co atoms and the increase in the volume fraction of the amorphous phase are retained as the major factors of this hard magnetic behavior of the present system.

Investigation and production of non-cytotoxic TixNbxSn (x = 5,10,15,20) alloys by high-energy mechanical milling with antibacterial activity

In this research, TixNbxSn (x = 5, 10, 15, 20 wt%) alloys were produced by high-energy mechanical alloying, and their potential applications as biomaterial were investigated through the microstructural characterizations (via XRD, SEM, and EDS analyses), mechanical tests (via hardness and elastic modulus tests), and biological studies (via antibacterial and cytotoxic tests). The alloying studies were carried out at room temperature in a high-energy ball milling for 8 h followed by a consolidation using a uniaxial pressing and 2 h pressureless sintering at 1150 °C. The XRD and EDS analyses showed that α-Ti, β-Ti, and TiC phases were present in the microstructure after sintering at high-temperature. Hardness tests revealed a wide range of values between 384 and 723 HV depending on the alloy compositions. That is, the volume fraction of TiC phase formed during processing and the ratio of α-Ti/β-Ti phases appear to control the hardness of the alloys. The elastic modulus was determined ranging from 70 to 103 GPa as a function of compositions with Ti15Nb15Sn alloy having the closest elastic modulus to the bone. The biological investigations revealed that TiNbSn alloys exhibited antibacterial properties against Staphylococcus aureus (S. aureus) and were not cytotoxic to healthy cells, regardless of their compositions. Furthermore, the findings indicated that when the cells were subjected to various dilutions of alloy extracts, there was a noticeable enhancement in both cell proliferation and viability. These findings have the potential to pave the way for novel approaches in the creation of TiNbSn alloys as biomaterials.

Effect of in-situ formed oxide and carbide phases on microstructure and corrosion behavior of Zr/Y doped CoCrFeNi high entropy alloys prepared by mechanical alloying and spark plasma sintering

The present work has examined the microstructural evolution, thermal stability, hardness, and corrosion behavior of Zr/Y doped CoCrFeNi HEAs prepared through high-energy mechanical alloying followed by spark plasma sintering (SPS) at 1100 °C. The achieved microstructures were investigated by XRD and TEM techniques. The results showed that investigated HEAs consist of an fcc solid solution of CoCrFeNi matrix with in-situ formed Cr–C carbides and Cr/Zr/Y based oxide phases. The SPS processing of CoCrFeNi yielded grain growth to 370 ± 60 nm, while 240 ± 160 nm grain size with bimodal grain size distribution and 165 ± 38 nm grain size were achieved with Zr and Y additions, respectively. The effects of microstructural changes on the hardness and corrosion behaviors of HEAs were also investigated. Compared with 372 ± 15 HV hardness of CoCrFeNi HEA, 445 ± 26 HV and 563 ± 58 HV hardness values were determined with Zr and Y doped HEAs, respectively. The increase in hardness is mainly ascribed to the precipitation strengthening of carbide and oxide phases as well as smaller grain sizes. The corrosion analysis showed that, although the achieved smaller grain sizes and the presence of different oxide types when dopped with Y and Zr impaired the corrosion resistance, the investigated HEAs have reasonable resistance to corrosion when compared to SS304 stainless steel.

Bonding mechanism and microstructural evolution in mechanically-alloyed nanodiamond-reinforced Al6061 composite particle deposits in cold spray

This study aimed at synthesizing a novel Al6061-ND metal matrix composite (MMC) particle feedstock via high-energy mechanical alloying (HE-MA) method for potential lightweighting applications. A material/milling design-of-experiment (DOE) was carried out to optimize the design parameters, including composite batch design, milling time, and ball diameter. It was found that the 5-mm diameter ball with 10:1 ball-to-powder ratio (BPR) could achieve the desired 5–100 μm particle size distribution (PSD) target with up to an 80 % yield within 2–4 h milling. Specifically, the addition of 1 wt% nanodiamond (ND), as opposed to 5 wt% or 10 wt%, in the MMC composite merited in its ability to produce superior PSD of the desired range. Despite milling being conducted in a controlled environment, oxide content was traced in the milled product indicating the need for a material-specific heat-treatment strategy incorporation. X-ray diffraction (XRD) analysis of both particles and deposits containing Al6061-1wt.%ND MMC revealed that (1) the synthesized Al6061 matrix contained nano crystallites in the order of 10–20 nm range; and (2) are linked to the pinning effect of the embedded ND in the matrix, respectively. High-resolution transmission electron microscopy (HRTEM) confirmed the formation of atomic-scale metallurgical bonding at the deposit-substrate interface, with conclusive evidence of the presence of ND in the Al matrix. Overall, the Al6061-1wt.%ND MMC, with optimized HE-MA synthesis method, was found to be a suitable candidate as feedstock for cold spray additive manufacturing of lightweight components.

Micro-hydroxyapatite reinforced Ti-based composite with tailored characteristics to minimize stress-shielding impact in bio-implant applications

Biomaterials having higher strength and increased bioactivity are widely researched topics in the area of scaffold and implant fabrication. Metal-based biomaterials are favorably suitable for load-bearing implants due to their outstanding mechanical and structural properties. The issue with pure metallic material used for bio-implant is the mismatch between the mechanical properties of the human body parts and the implant. The mismatch in modulus and hardness values causes damage to muscles and other body parts due to the phenomena of ‘stress-shielding’. As per the rule of mixture, combining a biocompatible ceramic with metals will not only lower the overall mechanical strength, but will also enhance the composite's bioactivity. In the present work, a Metal-Ceramic composite of Ti and μ-HAp is processed through high-energy mechanical alloying. The μ-HAp powders (in a weight fraction of 1%, 2%, and 3%) were alloyed with Pure Ti powder sintered using microwave hybrid heating (MHH). The homogeneously alloyed materials were inspected for chemical and elemental characteristics using XRD, SEM-EDX, and FTIR analyses. Nano-mechanical and micro-hardness properties were inspected for the fabricated Ti- μ-HAp composites and it shows a decreasing trend. Elastic modulus declined from 130.8 GPa to 50.11 GPa for 3 wt% μ-HAp compared to pure-Ti sample. The mechanical behaviour of developed composites confirms that it can minimize the stress-shielding impact due to comparatively lesser strength and hardness than pure metallic samples.

Wear behavior of in-situ oxide dispersion strengthened Fe-8Ni alloy with Zr additions

In this study, in-situ oxide dispersion strengthened (ODS) Fe91Ni8Zr1 and Fe88Ni8Zr4 alloys were produced by combination of high energy mechanical alloying (HEMA) and high temperature equal channel angular extrusion (HT-ECAE). The wear behaviors of the consolidated samples were investigated under different loads from 1 N to 4 N by reciprocating wear tests at room temperature. The Scanning electron microscopy (SEM) was used to examine the wear tracks to analyze the wear characteristics as a function of applied loads. The relative comparison of the wear results showed that under the lower loads of 1 N and 2 N, Fe88Ni8Zr4 alloy has lower wear rate than Fe91Ni8Zr1 alloy whereas under the higher loads of 3 N and 4 N, it is vice versa. Additionally, the friction coefficient of Fe91Ni8Zr1 alloy was found to be lower than that of Fe88Ni8Zr4 alloy under all the applied loads. The results were comparatively discussed with respect to microstructural features of 1 at% Zr and 4 at% Zr containing ODS alloys produced by HEMA followed by ECAE. The obtained results of ODS alloys with different grain size, precipitate size, and number density of the precipitates, may disclose a new sight for using such alloys in wear applications just as cutting tools, turbine blades, and discs.

Removal of Reactive Black 5 Azo Dye from Aqueous Solutions by a Combination of Reduction and Natural Adsorbents Processes

In this study, a combined process of reduction and adsorption for the degradation of azo dye with nanocrystalline Fe80Si10B10 powder as a reducing agent is analyzed. A mechanical alloying technique produced the powdered alloys needed for the redox process. The synthesized nanocrystalline structure favors the efficiency of the reduction step of Reactive Black 5 (RB5) azo dye. According to the UV-Vis analysis, the reductive process alone allowed for nearly complete color removal after 3 min of reaction. In this regard, the nanocrystallized FeSiB powder has excellent application potential in the first step of the reduction processes for degrading azo dye solutions. Indeed, the nanocrystalline FeSiB powder outperforms commercial Fe powders in terms of degradation efficiency because of the formation of multiple micro-batteries between the α-Fe solid solution and the Fe3Si nanocrystalline phases, favoring the loss of electrons from iron and exhibiting different corrosion resistance. In the second step, the adsorption process, the efficient removal of intermediate undesired compounds from the reduction processes, principally aromatic amines, is analyzed. Different adsorbents, including wood, graphene oxide, activated carbon, and pine particles, were used. The results suggest that graphene oxide and activate carbon performed the best for secondary product adsorption following RB5 degradation. The current study could serve as a guide for environmental applications, such as industrial wastewater treatment, using metallic powders produced by high-energy mechanical alloying.

Nanostructured Ni(Zn)–Al2O3 cermet particle synthesis in high-energy mechanical alloying method (CG-3:IL07)

Ceramic-metallics (cermets) have emerged as an important class of composite material combining favorable properties of their constitutive phases. In this work, nanostructured cermet Ni(Zn)–Al2O3 composition was synthesized using the high-energy mechanical alloying (HE-MA) method to be deployed as a cold spray deposition powder feedstock. Pre-milled Ni(Zn) alloy particles were mechanically mixed followed by milling in a SPEX™ 8000 M High Energy Ball Mill at a fixed 1050 rpm. The material design-of-experiment (DoE) involved two design compositions (30 wt% and 50 wt% α-alumina) with two substitutional alloy compositions, Ni(5 wt%Zn) and Ni(10 wt%Zn), along with milling time as a process variable. Microstructural characterization confirmed the embedment of nanoscale Al2O3 grain in micron-scale Ni(Zn) alloy particles. Additionally, EBSD analysis of Ni(Zn) alloy particles revealed that Ni(5 wt%Zn) experienced more uniform plastic deformation, work hardening and subsequent fracturing when compared to Ni(10 wt% Zn) alloy particles. The particle size measurement was carried out by laser diffraction showed that the cermet particles milled for 4 h had the desired size range for the objective of cold spraying. Also, the embedment of alumina into the Ni(Zn) alloy matrix and thereby, homogenization of cermet particles enhanced with the increase in milling time.

Mechanochemical Synthesis of Sustainable Ternary and Quaternary Nanostructured Cu2SnS3, Cu2ZnSnS4, and Cu2ZnSnSe4 Chalcogenides for Thermoelectric Applications

Copper-based chalcogenides have emerged as promising thermoelectric materials due to their high thermoelectric performance, tunable transport properties, earth abundance and low toxicity. We have presented an overview of experimental results and first-principal calculations investigating the thermoelectric properties of various polymorphs of Cu2SnS3 (CTS), Cu2ZnSnS4 (CZTS), and Cu2ZnSnSe4 (CZTSe) synthesized by high-energy reactive mechanical alloying (ball milling). Of particular interest are the disordered polymorphs of these materials, which exhibit phonon-glass-electron-crystal behavior-a decoupling of electron and phonon transport properties. The interplay of cationic disorder and nanostructuring leads to ultra-low thermal conductivities while enhancing electronic transport. These beneficial transport properties are the consequence of a plethora of features, including trap states, anharmonicity, rattling, and conductive surface states, both topologically trivial and non-trivial. Based on experimental results and computational methods, this report aims to elucidate the details of the electronic and lattice transport properties, thereby confirming that the higher thermoelectric (TE) performance of disordered polymorphs is essentially due to their complex crystallographic structures. In addition, we have presented synchrotron X-ray diffraction (SR-XRD) measurements and ab initio molecular dynamics (AIMD) simulations of the root-mean-square displacement (RMSD) in these materials, confirming anharmonicity and bond inhomogeneity for disordered polymorphs.

Phase Formation of Iron-Based Superconductors during Mechanical Alloying

We successfully synthesized bulk Ba0.6Na0.4Fe2As2 and Sr0.5Na0.5Fe2As2 compounds by high-energy mechanical alloying (MA) technique. The MA process results in homogeneous amorphous phases of BaFe2As2 and SrFe2As2. It was found that the optimum time for high-energy milling in all cases is about 1.5-2 h, and the maximum amount of amorphous phase could be obtained when energy of 50-100 MJ/kg was absorbed by the powder. After a short-term heat treatment, we obtained nearly optimum sodium-doped Ba1-xNaxFe2As2 and Sr1-xNaxFe2As2 superconducting bulk samples. Therefore, MA is a potential scalable method to produce bulk superconducting material for industrial needs.

Thermoelectric performance in disordered Cu2ZnSnSe4 nanostructures driven by ultra-low thermal conductivity

High-energy reactive mechanical alloying (ball milling) was used to synthesize tetragonal and cubic polymorphs of Cu2ZnSnSe4. The ordered tetragonal (I-4) polymorph undergoes a phase transition above 400 K into a Cu-Zn disordered tetragonal (I-42 m) polymorph, while the cubic (F-43 m) polymorph with full cation disorder is stabilized at room temperature. Both polymorphs show ultra-low thermal conductivities, 0.42 W m−1 K−1 at 722 K and 0.21 W m−1 K−1 at 523 K for the disordered tetragonal and cubic phases respectively. The cubic polymorph has a higher zT in the low-temperature range, peaking at 0.26 (523 K), while the disordered tetragonal has a maximum zT of 0.46 at 712 K. The latter is the highest reported zT for stoichiometric Cu2ZnSnSe4, comparable to the best-performing doped materials in the literature. A combination of experimental results and ab-initio calculations point to a coupling between structural disorder and microstructure as the mechanism behind the reported performance.

Effect of milling energy on phase transformation of Ti-Ni powders during mechanical alloying

ABSTRACT The effect of milling energy on the phase evolution of mechanically alloyed Ti–Ni powders is reported. Alloys were produced by low-energy and high-energy mechanical alloying (LEMA and HEMA, respectively). Powders milled for different times were characterised by X-ray diffraction and scanning electron microscopy. The phase transformations of powders milled by LEMA and HEMA before amorphisation are presented. During LEMA, TiNi, TiNi3, Ti3Ni4, and Ti2Ni were formed at 50 and 100 h. At these times, the results were consistent with the Ti–Ni equilibrium phase diagram. Up to 7.27 wt% of TiNi with a crystallite size of 32.63 ± 0.01 nm appeared at 50–75 h. During HEMA, iron contamination inhibited the formation of the TiNi phase at short milling times, and up to 47.9% of Fe0.2Ni4.8Ti5 was generated. These results indicate that amorphisation and heat treatment are not the only methods of promoting phase transformation in Ti–Ni alloys.

Mechanisms of electrochemical magnesium (de)alloying of Mg-Sn and Mg-Pb polymorphs

Different polymorphs of Mg-Sn and Mg-Pb intermetallic compounds were prepared by high-energy mechanical alloying and then investigated as active material in magnesium batteries. Beside thermodynamically stable Mg2Sn and Mg2Pb crystallizing in the anti-fluorite structure, other polymorphs Mg∼2Sn and Mg∼2Pb were prepared by increasing the ball-milling time. The first dealloying process is almost complete only for the cubic polymorphs, then similar capacities are observed during the subsequent alloying and dealloying sequences. Thanks to operando X-ray diffraction, the electrochemical mechanism is revealed and shows that the cubic polymorphs Mg2Sn and Mg2Pb tend to preferentially form during the alloying whatever the pristine intermetallic. Weak traces of Mg∼2Sn and Mg∼2Pb are observed during the alloying, suggesting that these polymorphs act as a by-product and/or an intermediate phases of the electrochemical process. Finally, the compatibility of cubic Mg2Sn and Mg2Pb with Mg(TFSI)2-based electrolyte is confirmed in full cell vs. a positive electrode based on the Chevrel phase Mo6S8, although limited performance is achieved. This fundamental work provides new insights in the behavior of alloy-type negative electrodes for magnesium-ion batteries.

An investigation of abnormal grain growth in Zr doped CoCrFeNi HEAs through in-situ formed oxide phases

Abnormal grain growth (AGG) in nanocrystalline (CoCrFeNi)100-xZrx (x = 1 and 4 at. %) HEAs, prepared through high energy mechanical alloying, was comprehensively investigated upon annealing. Transmission electron microscopy (TEM), including high angle annular dark field imaging (HAADF) and energy dispersive spectroscopy (EDS) mapping, focused ion beam microscopy (FIB), and X-ray diffraction experiments (XRD) were utilized to investigate the microstructures as a function of added Zr content and temperature exposures. The results showed that nanocrystalline grains of the as-milled HEAs did not increase significantly upon annealing up to 700 °C as the nanocrystalline grain sizes were retained. However, grain growth was observed in (CoCrFeNi)99Zr1 after annealing at 900 °C, which turned into AGG after annealing at a higher temperature of 1100 °C, disrupting the equiaxed grain structures observed at 900 °C. Although the increased amount of Zr doping reduced the average grain size in (CoCrFeNi)96Zr4, bimodal grain structure existed in the microstructure composed of a matrix with 255 nm grain size and abnormally grown grains up to 3 μm. The observed AGG was attributed to the pinning effect of in-situ formed secondary oxide phases. The microstructural evolution as a function of Zr doping and annealing temperatures was also correlated with the microhardness test results. The AGG and bimodal grain structure reported for the Zr doped CoCrFeNi HEA may open a new avenue to produce HEAs with the enhanced strength-ductility combination due to the incorporation of larger grains and in-situ formed oxide phases in a fine-grained matrix.

Elimination of Composition Segregation in 33Al-45Cu-22Fe (at.%) Powder by Two-Stage High-Energy Mechanical Alloying.

In the present work, complex powder alloys containing spinel as a minor phase were produced by mechanical alloying in a high-energy planetary ball mill from a 33Al–45Cu–22Fe (at.%) powder blend. These alloys show characteristics suitable for the synthesis of promising catalysts. The alloying was conducted in two stages: at the first stage, a Cu+Fe powder mixture was ball-milled for 90 min; at the second stage, Al was added, and the milling process was continued for another 24 min. The main products of mechanical alloying formed at each stage were studied using X-ray diffraction phase analysis, Mössbauer spectroscopy, transmission electron microscopy, and energy-dispersive spectroscopy. At the end of the first stage, crystalline iron was not found. The main product of the first stage was a metastable Cu(Fe) solid solution with a face-centered cubic structure. At the second stage, the Cu(Fe) solid solution transformed to Cu(Al), several Fe-containing amorphous phases, and a spinel phase. The products of the two-stage process were different from those of the single-stage mechanical alloying of the ternary elemental powder mixture; the formation of undesirable intermediate phases was avoided, which ensured excellent composition uniformity. A sequence of solid-state reactions occurring during mechanical alloying was proposed. Mesopores and a spinel phase were the features of the two-stage milled material (both are desirable for the target catalyst).

Microstructure and Mechanical Properties of Spark Plasma Sintered Mg-Zn-Ca-Pr Alloy

Alloys based on magnesium are of considerable scientific interest as they have very attractive mechanical and biological properties that could be used to manufacture biodegradable materials for medical applications. Mechanical alloying is a very suitable process to obtain alloys that are normally hard to produce as it allows for solid-state diffusion via highly energetic milling, producing fine powders. Powders obtained by this method can be sintered into nearly net-shape products, moreover, their phase and chemical composition can be specifically tailored. This work aims to investigate the effect of milling time on the density, microstructure, phase composition, and mechanical properties of Mg-Zn-Ca-Pr powders processed by high energy mechanical alloying (HEMA) and consolidated by spark plasma sintering (SPS). Thus, the results of XRD phase analysis, particle size distribution (granulometry), density, mechanical properties, SEM investigation of mechanically alloyed and sintered Mg-Zn-Ca-Pr alloy are presented in this manuscript. The obtained results illustrate how mechanical alloying can be used to produce amorphous and crystalline materials, which can be sintered and demonstrates how the milling time impacts their microstructure, phase composition, and resulting mechanical properties.

Static and dynamic components of Debye-Waller coefficients in the novel cubic polymorph of low-temperature disordered Cu2ZnSnS4.

Cu2ZnSnS4 (CZTS) is an attractive material for sustainable photovoltaics and thermoelectrics, and several properties originate from its marked polymorphism. High-energy mechanical alloying is found to lead to a disordered phase that possesses a sphalerite-like cubic structure. This is investigated in detail with the aid of laboratory and synchrotron radiation X-ray diffraction, Raman spectroscopy, electron microscopy and ab initio molecular dynamics. The disordered cubic polymorph is preserved below 663 K. With thermal treatments above 663 K, the tetragonal kesterite phase forms, used here as a reference for structural and microstructural features. Particular attention is paid to the stacking arrangement: a significant fraction of twin faults was found in the disordered cubic samples, which then progressively annealed with domain growth and with the transition to the ordered tetragonal phase. This study also focuses on Debye-Waller coefficients, which were found to be considerably larger for the disordered cubic than the tetragonal sample. Indeed, disorder leads to an ∼1 Å2 upward shift through the temperature range 100-700 K, a feature confirmed by ab initio calculations, which points to a particularly high contribution from disordered Sn cations. This supports the general understanding that structural disorder introduces a temperature-independent static contribution to the atomic mean-square displacement. Debye-Waller coefficients are found to be a good measure of this disorder, known to have a critical effect on transport properties.

Structure and properties of powder alloys Fe–(45-15)%Ni–(10-5)%Cu, obtained via mechanical alloying

The article investigates the structure and properties of Fe–(45-15)%Ni–(10-5)%Cu powder alloys. The production method included low- and high-energy (mechanical alloying, МА) treatment of Fe, Ni, and Cu powders in a planetary ball mills followed by hot-pressing of mixes at 950 °С. After MA, the mixtures consist of composite granules with a lamellar structure and particle size of 10–100 μm. After low-energy treatment, three phases were detected by XRD in hot-pressed samples: α-Fe-based solid solution BCC-(Fe, Ni, Cu), Ni-based solid solution FCC-(Ni, Fe, Cu), and FCC-FeO. The appearance of FeO is caused by the partial oxidation of iron during mixing and hot pressing. The total oxide content does not exceed 1.3 wt%. For Fe-X% Ni-5% Cu alloys the ultimate bending strength depends on the nickel content (X, %) linearly according to the equation σben = −19⋅X + 1995 [MPa], where 15 % ≤ X ≤45 %. Alloys obtained by MA have a homogeneous structure and depending on the composition can be either two- or three-phase. As a result of MA the hardness of the alloys increased by 20–21 HRB, and the ultimate bending strength increases by 300–540 MPa. The alloy with the composition 80%Fe-15%Ni-5%Cu has the maximum bending strength σben = 2135 ± 60 MPa. The wear of MA alloys is (4.1–4.4)⋅10−5 mm3 /(N⋅m) which is more than two times lower than the wear of alloys obtained by low-energy treatment. This work was carried out with financial support from the Russian Science Foundation (Project No. 17-79-20384).