This work deals with the characterization of structure, magnetic and mechanical properties of (FeNiCo)100-x(AlSi)x (x = 0, 5, 10, 15, 25) multicomponent alloys prepared by casting. The results of ...X-ray diffraction measurements, scanning electron microscopy observations and hardness and magnetic properties investigations are presented. The studies show that cast (FeNiCo)100-x(AlSi)x alloys reveal dendritic morphology and their phase composition depends on (Al + Si) content. For x ≤ 10 a face-centered cubic phase is observed, while the increase of Al and Si content results in a body-centered cubic phase formation. It leads to a fivefold increase of hardness from 88 HV to 526 HV. The investigated alloys have high magnetic induction reaching 170 emu/g, while their coercivity value is even up to 2.9 kA/m for x = 15, and strongly depends on chemical and phase composition.
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•TiB2/TiC – Ni composites have been successfully fabricated by PPS.•The composites revealed the density above 99% and high hardness of 2400HV.•Due to double-step sintering process ...sintering temperature was as low as 1100 °C.•Undesirable phases like Ni3B or graphite has been avoided.
TiB2/TiC – Ni composites were synthesized starting from the powders of Ti, B4C and Ni, using Pulse Plasma Sintering (PPS) method. Typically used one-step (1100 °C–10 min.) and novel double-step sintering processes (900 °C–10 min. +1100 °C–5 min.) were applied and compared. XRD studies showed that the composite obtained by double-step sintering consisted of TiB2, TiC and Ni phases. For one-step processing additionally undesired Ni3B and graphite were detected. SEM observations revealed dark-grey grains of TiB2, light-grey grains of TiC (both around 25 µm in size) and Ni areas surrounded by TiC. The composites synthesized in one- and double-step processes revealed the hardness and relative density of 2335 HV5 (±110) and 97.8% and 2470 HV5 (±70) and 99.8%, respectively. Novel double-step sintering process allowed to avoid undesired phases (graphite, Ni3B) and only TiB2, TiC and Ni were present in the structure. Additionally it was possible to decrease the temperature of the process comparing to other fabrication methods.
W-Y2O3 composites obtained by mechanical alloying and sintering Antolak-Dudka, A.; Oleszak, D.; Zielinski, R. ...
Advanced powder technology : the international journal of the Society of Powder Technology, Japan,
February 2021, 2021-02-00, Letnik:
32, Številka:
2
Journal Article
Recenzirano
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•W-Y2O3 composites were manufactured by mechanical alloying and powder sintering.•The content of the Y2O3 strengthening phase was 5 and 10 wt%•During milling, a W-based solid solution ...was formed.•After sintering, new phases appeared in addition to the W-based solid solution.•The sinters’ microhardness increases with the increasing content of Y2O3.
The aim of this work was to manufacture tungsten composites from different initial powder mixtures by mechanical alloying followed by sintering. Two initial powder mixtures, W + 5 wt% of Y2O3 and W + 10 wt% of Y2O3, and pure W for comparison were mechanically alloyed for 50 h in a Fritsch Pulverisette P5 planetary ball mill under an argon atmosphere. The final products were consolidated by pulse plasma sintering at 1640 °C under a pressure of 20 MPa. The powders and consolidated pellets were examined by the XRD method. The obtained results show that during milling, the tungsten based solid solution formed. After consolidation, the XRD examination revealed that in addition to the tungsten-based solid solution and yttria, new carbide phases (Fe3C, WC, W2C and Fe3W3C) appeared. The graphite present in the carbides originated from the die used in the sintering process. SEM observations of the surfaces of the sinters revealed that the microstructure is not homogeneous and consists of areas rich in one or two elements, such as W, C, Fe or the Y2O3 phase. The microhardness of the pellets increases with the increasing content of the Y2O3 strengthening phase, whereas the values of the relative density decrease.
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•Al-based composites were fabricated by High Pressure High Temperature method.•Crystallization of amorphous phase was avoided even at high sintering temperature.•Partial decomposition ...of Al-based solid solution was observed.•Significant increase of hardness was observed, if compared with crystalline matrix.
Commercial crystalline AA4048 powders and mechanically alloyed amorphous Al60Nb40 (at.%) powders were used for fabrication of crystalline-amorphous composites containing 10, 20 and 30 vol% of amorphous phase. High pressure high temperature technique was used for powders compaction. The applied pressure was 7.7 GPa and temperature was in the range 600–1000 °C. The powders and bulk samples were characterized by structural investigations (X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, X-ray fluorescence spectroscopy), hardness and microhardness tests and measurements of density. The obtained sinters revealed relative density above 98.7%. The amorphous component was observed as agglomerates or as single particles surrounding the grains of crystalline AA4048 phase. The crystallization of amorphous phase was not observed. Simultaneously, up to 2.5 wt% of Fe was detected as impurity from milling media. Significant increase of hardness was observed, from 226 to 288HB, resulting from the presence of amorphous component which prevent from cracks propagation during deformation.
•Nanocomposite alloys were formed by annealing of the rapidly quenched alloys.•Magnetically hard L10 (Fe,Co)Pt and soft (Fe,Co)2B or (Fe,Co)B were formed.•Mössbauer spectra revealed Co substitution ...for Fe in L10 FePt, FeB and Fe2B phases.•Annealed alloys exhibit hard magnetic properties which depend on phase compositions.•Co addition was found to decrease the magnetization and the energy product.
The influence of Co content on the structural and hard magnetic properties of two sets of nanocrystalline Fe52−xCoxPt28B20 (x=0–26) and Fe60−yCoyPt25B15 (y=0–40) alloys was studied. The alloys were prepared as ribbons by the rapid quenching technique. The nanocomposite structure in the alloys was obtained by annealing at 840–880K for 30min. Structural characterization of the samples was performed using the Mössbauer spectroscopy and X-ray diffraction. Magnetic properties of the samples were studied by the measurements of the hysteresis loops and of the magnetization at increasing temperatures. An amorphous phase prevailed in the as-quenched Fe52−xCoxPt28B20 alloys while a disordered solid solution of fcc-(Fe,Co)Pt was a dominating phase in the Fe60−yCoyPt25B15 ribbons. Differential scanning calorimetry measurements revealed one or two exothermic peaks at temperatures up to 993K, depending on the composition of the alloys. Thermal treatment of the samples led to the formation of the magnetically hard ordered L10 tetragonal (Fe,Co)Pt nanocrystallites and magnetically softer phases of (Fe,Co)B (for Fe52−xCoxPt28B20) or (Fe,Co)2B (for Fe60−yCoyPt25B15). Detailed Mössbauer spectroscopy studies revealed that cobalt substituted for iron in both the L10 phase and in iron borides. The nanocomposite Fe60−yCoyPt25B15 alloys exhibited significantly larger magnetic remanence and maximum energy products but a smaller coercivity than those observed for the Fe52−xCoxPt28B20 alloys. Co addition caused a reduction of the magnetization and the energy product in both series of the alloys. The largest magnetic remanence of 0.87T and the highest energy product (BH)max=80kJ/m3 were obtained for the Co-free Fe52Pt28B20 alloy while the largest coercivity (HC>950kA/m) was observed for the Fe50Co10Pt25B15 and Fe30Co30Pt25B15 alloys. Differences in the hard magnetic properties of the nanocomposite alloys were related to different phase compositions influencing the strength of inter-phase exchange coupling interactions.
The results of research on preparations of alloy Ni-B/B composite coatings produced by chemical reduction method on a carbon steel substrate are collected in this paper. The alloy Ni-B coatings were ...also investigated for comparative purposes. The produced coatings were subjected to a heat treatment process. The boron powder with the particles size below 1 µm was used as the dispersion phase. The structure of the coatings was examined by X-ray diffraction method. Boron powder particles as well as surface morphology and topography were characterized by scanning electron microscopy. The roughness test, microhardness and corrosion resistance by potentiodynamic method and surface wettability tests were carried out. Analysis of the chemical composition by the EDS method showed that the boron powder particles were evenly embedded in the entire volume of the coating. Ni-B/B composite coatings are characterized by higher hardness than alloy Ni-B coatings. As a result of heat treatment, the Ni3B phase crystallized, which increased the hardness of the coating material. The incorporation of boron powder particles and heat treatment reduce the corrosion resistance of coatings. All produced coatings exhibited hydrophobic properties.
Deep cryogenic treatment (DCT) is gaining popularity as a treatment used to modify structures obtained during heat or thermo-chemical treatment. The article presents the influence of DCT, carried out ...during heat treatment before and after gas nitriding processes, on the formation of gas nitrided layers on X153CrMoV12 steel. It was found that the use of DCT between quenching and tempering performed prior to gas nitriding processes, increases the hardness, thickness and wear resistance of the nitrided layers. At the same time, if we apply cryogenic treatment during post-heat treatment of nitrided layers, we also get very high wear resistance and increased thickness of nitrided layers, in comparison with conventional gas nitriding of X153CrMoV12 steel. In this case, DCT significantly increases also the hardness of the core by the transformation of retained austenite and the precipitation of fine carbides of alloying elements.
In this study, synthesis of titanium diboride from elemental powders of Ti and B by electric discharge assisted mechanical milling technique was investigated. This recently developed technique has ...the following advantages: rapid reaction rate, controlled reaction, direct reaction between Ti and B without adding another element into the system and cost effectiveness. TiB2 samples were prepared using an in-house built reactor with an ac high voltage transformer, generating impulses within kV/mA range. The structures of reaction products were characterized by X-ray diffractometry, and powder morphologies by SEM. X-ray diffraction studies showed that the milling product was TiB2 with small fraction of TiB.
The aim of these studies was to obtain single phase cubic modification of Li7La3Zr2O12 by mechanical milling and annealing of La(OH)3, Li2CO3 and ZrO2 powder mixture. Fritsch P5 planetary ball mill, ...Rigaku MiniFlex II X-ray diffractometer, Setaram TG-DSC 1500 analyser and FEI Titan 80-300 transmission electron microscope were used for sample preparation and investigations. The applied milling and annealing parameters allowed to obtain the significant contribution of c-Li7La3Zr2O12 in the sample structure, reaching 90%. Thermal measurements revealed more complex reactions requiring further studies.
X-ray diffraction and Moessbauer spectroscopy were applied as complementary methods to investigate the structure and hyperfine interactions in the Bi9Ti3Fe5O27 compound. Samples were synthesized by ...the solid-state sintering method at various temperatures as well as by mechanical alloying. An X-ray diffraction analysis proved that the sintered compounds formed single phases at a temperature above 993K, while the mechanosynthesized material needed additional thermal treatment to complete the single phase formation. Moessbauer studies confirmed the diffraction measurements. Compounds, both those prepared by a solid-state route and fired at 993K and those mechanically alloyed contained residual hematite, however, those sintered at elevated temperatures and mechanically alloyed and subsequently annealed at 1173K were single-phased materials. Room-temperature Moessbauer spectra of the Bi9Ti3Fe5O27 compound revealed their paramagnetic properties suggesting that the Neel temperature of this ceramic was lower than room temperature.
