scholarly journals Structure of Alloys for (Sm,Zr)(Co,Cu,Fe)z Permanent Magnets: III. Matrix and Phases of the High-Coercivity State

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7762
Author(s):  
Andrey G. Dormidontov ◽  
Natalia B. Kolchugina ◽  
Nikolay A. Dormidontov ◽  
Mark V. Zheleznyi ◽  
Anna S. Bakulina ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Domain Structure ◽  
Structural Component ◽  
Permanent Magnets ◽  
Phase State ◽  
Volume Fraction ◽  
Heat Treatments ◽  
High Coercivity ◽  
Structural Components ◽  
The Matrix

Observations of the surface domain structure (Kerr-effect), optical metallography, scanning electron microscopy (SEM-SE), and electron microprobe analysis (EPMA-SEM), measurements of major and minor magnetic hysteretic loops were used to study pseudo-single-crystal samples of (Sm,Zr)(Co,Cu,Fe)z alloys subjected to heat treatments to the high-coercivity state, which are used in fabricating sintered permanent magnets. Correlations between the chemical composition, hysteretic properties, structural components, domain structure, and phase state were determined for the concentration ranges that ensure wide variations of 4f-/4d-/3d-element ratio in the studied samples. The phase state formed by collinear and coherent phase components determines the high coercive force and ultimate magnetic hysteresis loops of the pseudo-single crystals. It was found that the 1:5 phase with the hexagonal structure (P6/mmm) is the matrix of the alloys for (Sm,Zr)(Co,Cu,Fe)z permanent magnets; the matrix undergoes phase transformations in the course of all heat treatments for the high-coercivity state. The heterogeneity observed with optical magnifications, namely, the observation of main structural components A and B, is due to the alternation, within the common matrix, of regions with modulated quasi-spherical precipitates and regions with hexagonal bipyramids (cellular phase) although, traditionally, many investigators consider the cellular phase as the matrix. It is shown that the relationship of volume fractions of structural components A and B that account for more than 0.9 volume fraction of the total, which is due to the integral chemical composition of the alloys, determines the main hysteretic performances of the samples. The Zr-rich phases, such as 5:19, 2:7, and 6:23, and a structural component with the variable stoichiometry (Sm(Co,Cu,Fe)3.5–5) that is almost free of Zr and contains up to 33 at% Cu, were found only within structural component A in quantities sufficient for EPMA analysis.

scholarly journals Structure of Alloys for (Sm,Zr)(Co,Cu,Fe)Z Permanent Magnets: First Level of Heterogeneity

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3893 ◽  
Author(s):  
Andrey G. Dormidontov ◽  
Natalia B. Kolchugina ◽  
Nikolay A. Dormidontov ◽  
Yury V. Milov
Keyword(s):  
Phase Composition ◽  
Quantitative Analysis ◽  
Chemical Composition ◽  
Permanent Magnets ◽  
Composition Range ◽  
Structural Phase ◽  
High Coercivity ◽  
Structural Components ◽  
Structural Formation ◽  
Hysteretic Properties

An original vision for the structural formation of (Sm,Zr)(Co,Cu,Fe)Z alloys, the compositions of which show promise for manufacturing high-coercivity permanent magnets, is reported. Foundations arising from the quantitative analysis of alloy microstructures as the first, coarse, level of heterogeneity are considered. The structure of the alloys, in optical resolutions, is shown to be characterized by three structural phase components, which are denoted as A, B, and C and based on the 1:5, 2:17, and 2:7 phases, respectively. As the chemical composition of alloys changes monotonically, the quantitative relationships of the components A, B, and C vary over wide ranges. In this case, the hysteretic properties of the (Sm,Zr)(Co,Cu,Fe)Z alloys in the high-coercivity state are strictly controlled by the volume fractions of the A and B structural components. Based on quantitative relationships of the A, B, and C structural components for the (R,Zr)(Co,Cu,Fe)Z alloys with R = Gd or Sm, sketches of quasi-ternary sections of the (Co,Cu,Fe)-R-Zr phase diagrams at temperatures of 1160–1190 °C and isopleths for the 2:17–2:7 phase composition range of the (Co,Cu,Fe)–Sm–Zr system were constructed.

scholarly journals Structure of Alloys for (Sm,Zr)(Co,Cu,Fe)z Permanent Magnets: II. Composition, Magnetization Reversal, and Magnetic Hardening of Main Structural Components

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5426
Author(s):  
Andrey G. Dormidontov ◽  
Natalia B. Kolchugina ◽  
Nikolay A. Dormidontov ◽  
Yury V. Milov ◽  
Alexander S. Andreenko
Keyword(s):  
Phase Transformations ◽  
Domain Structure ◽  
Magnetization Reversal ◽  
Permanent Magnets ◽  
Hysteresis Loops ◽  
Total Sample ◽  
High Coercivity ◽  
Metallographic Analysis ◽  
Structural Components ◽  
Slow Cooling

Experimental series of alloys for (Sm,Zr)(Co,Cu,Fe)Z permanent magnets are presented in the concentration ranges that provide wide variations of (4f)/(4d)/(3d) ratios of comprising elements. Optical metallographic analysis, observation of the surface domain structure upon magnetization reversal (Kerr effect), electron microprobe analysis, and measuring the major hysteresis loops of samples at different stages of heat treatment are used to study processes related to the development of the highly coercive state of these samples. It was found that the volume fractions of two main structural components A and B, which comprise 90% of the total sample volume, rigorously control the coercivity at all stages of thermal aging. At the same time, structural components A and B themselves in samples being in the high-coercivity state differ qualitatively and quantitatively in the chemical composition, domain structure and its development in external magnetic fields and, therefore, are characterized by different morphologies of the phases comprising the structural components. Two stages of phase transformations in the sample structure are observed. During isothermal annealing, the cellular structure develops within the B component, whereas, during stepwise (slow) cooling or quenching from the isothermal aging temperature to 400 °C, a phase structure evolves within both the cell boundaries in B and the structural component A. The degree of completion of the phase transformations within micro- and nano-volumes of the components determines the ultimate hysteretic characteristics of the material.

scholarly journals Structural Investigations of Solidification and Heat Treatments Influence on High Alloyed Cast Irons Grades with Nb-V-Ti Additions

2009 ◽  
Vol 289-292 ◽  
pp. 77-86 ◽  
Author(s):  
Jacqueline Lecomte-Beckers ◽  
Jérôme Tchoufang Tchuindjang
Keyword(s):  
Phase Transformations ◽  
Volume Fraction ◽  
Raw Materials ◽  
Solidification Process ◽  
Heat Treatments ◽  
Hot Strip Mill ◽  
Cast Irons ◽  
Structural Investigations ◽  
Alloyed Cast ◽  
The Matrix

Two High Alloyed Cast Irons (HACI) were studied, both belonging to the Fe-C-Cr-Si-X system where X represented a strong carbide forming element. One of these alloys was obtained after adding Nb, V and Ti to the chemical composition of the other alloy. Raw materials originated from spun cast rolls for hot strip mill were submitted to different heat treatments routes, in order to study the influence of alloying elements on the microstructure. Both HACI grades contained a mixture of martensite and retained austenite matrix in the as-cast conditions and after quenching. Differential Thermal Analysis was carried out on the heat treated samples in order to determine the phase transformations occurring during re-melting and subsequent solidification sequence. Diffusionless transformations leading to various types of martensite were found in the matrix. Bulky NbC carbides precipitating at the beginning of the solidification process strongly influence the nature and the rate of the subsequent diffusional phase transformations, particularly for HACI grade with Nb, V and Ti additions. Quantitative metallography was done to determine graphite, NbC carbides, cementite and matrix volume fraction in HACI studied grades.

scholarly journals Cluster-Assembled Iron-Platinum Nanocomposite Permanent Magnets

2006 ◽  
Vol 962 ◽  
Author(s):  
Xiangxin Rui ◽  
Zhiguang Sun ◽  
Yingfan Xu ◽  
David J. Sellmyer ◽  
Jeffrey E. Shield
Keyword(s):  
Exchange Coupling ◽  
Permanent Magnets ◽  
Volume Fraction ◽  
High Energy ◽  
Heat Treatments ◽  
Processing Route ◽  
Soft Magnetic ◽  
Soft Phase ◽  
Energy Product ◽  
Post Deposition

ABSTRACTExchange-spring nanocomposite permanent magnets have received a great deal of attention for their potential for improved the energy products. Predicted results, however, has been elusive. Optimal properties rely on a uniformly fine nanostructure. Particularly, the soft magnetic phase must be below approximately 10 nm to ensure complete exchange coupling. Inert gas condensation (IGC) is an ideal processing route to produce sub-10 nm clusters method. Two distinct nanostructures have been produced. In the first, Fe clusters were embedded in an FePt matrix by alternate deposition from two sources. Fe cluster content ranged from 0 to 30 volume percent. Post-deposition multi-step heat treatments converted the FePt from the A1 to L10 structure. An energy product of approximately 21 MGOe was achieved. Properties deteriorated rapidly at cluster concentrations above 14 volume due to uncoupled soft magnetic regions (from cluster-cluster contacts) and cooperative reversal. The second nanostructure, designed to overcome those disadvantages, involved intra-cluster structuring. Here, Fe-rich Fe-Pt clusters separated by C or SiO2 were fabricated. Phase separation into Fe3Pt and FePt and ordering was induced during post-deposition multi-step heat treatments. By confining the soft and hard phases to individual clusters, full exchange coupling was accomplished and cooperative reversal between clusters was effectively eliminated. An energy product of more than 25 MGOe was achieved, and the volume fraction of the soft phase was increased to greater than 0.5 while maintaining a coercivity of 6.5 kOe. The results provide new insight into developing high energy product nanostructured permanent magnets.

Characterization and statistical modeling of the precipitation kinetics in the commercial aluminum alloy AA5182

2011 ◽  
Vol 1369 ◽  
Author(s):  
Zhenshan Liu ◽  
Volker Mohles ◽  
Olaf Engler ◽  
Günter Gottstein
Keyword(s):  
Volume Fraction ◽  
Experimental Information ◽  
Heat Treatments ◽  
Matrix Composition ◽  
Heating Process ◽  
Precipitation Kinetics ◽  
Unknown Parameters ◽  
Solute Content ◽  
Eds Analysis ◽  
The Matrix

ABSTRACTPrecipitation kinetics in the wrought alloy AA5182 during homogenization was investigated by various experimental methods. The constituents generated during casting were identified with energy dispersive X-ray spectroscopy (EDS) analysis. Their volume fraction was measured with optical microscopy. The size evolution of dispersoids during the heat treatment was studied in TEM. The EDS analysis shows that the dispersoids were mainly Al6Mn and α-Al(MnFe)Si. The dispersoids number was counted from a large number of electron back scatter images to yield good statistics. Electrical resistivity measurements were performed to study precipitation indirectly via the solute content. With the above experimental information, the thermodynamics based precipitation model ClaNG was calibrated for the alloy AA5182. Unknown parameters like interface energies of precipitates were adjusted accordingly. ClaNG is capable of describing the simultaneous nucleation, growth and coarsening of all important precipitates in multi-component systems for arbitrary heat treatments. After the unknown parameters were determined, the model was able to predict the volume and size distribution of dispersoids and the matrix composition for varied heat treatments. The predictions were used to design and optimize the heating process with respect to the microstructure of the homogenized ingot.

Effect of Heat Treatment on the Microstructure of Cu-Cr-Zr Alloy

2017 ◽  
Vol 727 ◽  
pp. 166-170 ◽  
Author(s):  
Li Jun Peng ◽  
Hao Feng Xie ◽  
Gao Lei Xu ◽  
Guo Jie Huang ◽  
Zhen Yang
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Volume Fraction ◽  
Homogenization Temperature ◽  
Eutectic Structure ◽  
Optical Microscope ◽  
Heat Treatments ◽  
Transmission Electron ◽  
The Matrix ◽  
Zr Alloy

Effect of Heat treatments on microstructure in a Cu-0.71Cr-0.12Zr alloy (in wt.%) have been investigated. The microstructures are analyzed by optical microscope, scanning electron microscope, transmission electron microscope and high-resolution transmission electron microscope after each step of heat treatments. The results show that the as-cast microstructure of Cu-Cr-Zr alloy is Cu matrix, Cr dendrite and eutectic structure which is composed of Cu and Cu5Zr phase with a fine lamellar structure. By increasing the homogenization temperature or prolonging the holding time, the eutectic structure is dissolved into the matrix gradually and the volume fraction of the Cr phases is obviously reduced. The precipitation of Cr phase prevents from Zr-rich phases dissolving in the matrix. And the proper homogenizing process is 900°C×12 h. When the alloy aged at 450°C for 24 h, the crystallography of Cr precipitates and the orientation relationship between Cr precipitates and Cu matrix is bcc structure and KS-OR, respectively. The disk-shaped precipitate is identified as Cu5Zr phase and their habit plane is parallel to {111}Cu plane.

scholarly journals Manufacturing with Application of Gpi Method and Selected Properties of Al Matrix Composites Reinforced Unidirectionally and Three-Directionally with Carbon Fibres/ Wytwarzanie Metodą Infiltracji Gazowej I Wybrane Własności Kompozytów Na Osnowie Aluminium, Umocnionych Jedno I Trójkierunkowo Włóknami Węglowymi

2014 ◽  
Vol 59 (4) ◽  
pp. 1539-1546
Author(s):  
M. Wojtaszek ◽  
A. Czulak
Keyword(s):  
Chemical Composition ◽  
Volume Fraction ◽  
Protective Layer ◽  
Carbon Fibres ◽  
Destructive Testing ◽  
Infiltration Process ◽  
Pressure Infiltration ◽  
Microstructure Observation ◽  
The Matrix ◽  
Al Matrix Composites

Abstract The discussion of the possibility of application of the GPI (gas pressure infiltration) process to the manufacturing of composites based on selected aluminium alloys reinforced with carbon fibres coated with nickel protective layer, as well as the determination of selected properties of materials obtained using this technique, is presented in the article. The composites reinforced unidirectionally (UD) were produced, the suitable volume fraction of fibres was determined and the proper forming parameters were established. Basing on the obtained results, with application of the same components, the composites reinforced three-directionally (3D) were subjected to infiltration. The preforms were designed and prepared using plaiting and joining methods. The GPI process parameters were verified for the assumed fibre arrangement. Thermal expansion of matrix alloys and composites obtained with application of most favourable parameters was determined and the influence of fibre arrangement and chemical composition of the matrix on the obtained results was analysed. The comparative abrasion tests with application of different velocities were performed for the selected alloy and the composite reinforced unidirectionally. In order to evaluate the changes taking place in the matrix during infiltration, the analysis of chemical composition of composites was performed for materials reinforced unidirectionally, as an example. The correctness of distribution of fibres in the composite matrix was also evaluated by means of microstructure observation as well as non-destructive testing with application of computed tomography technique. The results obtained during the investigations provide information concerning suitability and limitations of the GPI method to the manufacturing of light structural parts from the proposed components.

Influence of Heat Treatments on Microstructures in an Fe-Co-V Alloy

1974 ◽  
Vol 32 ◽  
pp. 512-513
Author(s):  
S. Mahajan ◽  
M. R. Pinnel ◽  
J. E. Bennett
Keyword(s):  
Single Phase ◽  
Alloy Composition ◽  
Supersaturated Solid Solution ◽  
Cell Formation ◽  
Heat Treatments ◽  
Air Cooling ◽  
Iced Brine ◽  
Transmission Electron ◽  
The Matrix ◽  
Bcc Structure

The microstructural changes in an Fe-Co-V alloy (composition by wt.%: 2.97 V, 48.70 Co, 47.34 Fe and balance impurities, such as C, P and Ni) resulting from different heat treatments have been evaluated by optical metallography and transmission electron microscopy. Results indicate that, on air cooling or quenching into iced-brine from the high temperature single phase ϒ (fcc) field, vanadium can be retained in a supersaturated solid solution (α2) which has bcc structure. For the range of cooling rates employed, a portion of the material appears to undergo the γ-α2 transformation massively and the remainder martensitically. Figure 1 shows dislocation topology in a region that may have transformed martensitically. Dislocations are homogeneously distributed throughout the matrix, and there is no evidence for cell formation. The majority of the dislocations project along the projections of <111> vectors onto the (111) plane, implying that they are predominantly of screw character.

Formation of Persistent Slip Band in Fatigued Copper Single Crystals

1982 ◽  
Vol 40 ◽  
pp. 470-471
Author(s):  
N. Y. Jin
Keyword(s):  
Volume Fraction ◽  
Fatigue Cracks ◽  
Wall Structure ◽  
Matrix Structure ◽  
Dislocation Dipole ◽  
Slip Bands ◽  
Persistent Slip Bands ◽  
The Matrix ◽  
Hard Shell ◽  
Copper Single Crystals

Localised plastic deformation in Persistent Slip Bands(PSBs) is a characteristic feature of fatigue in many materials. The dislocation structure in the PSBs contains regularly spaced dislocation dipole walls occupying a volume fraction of around 10%. The remainder of the specimen, the inactive "matrix", contains dislocation veins at a volume fraction of 50% or more. Walls and veins are both separated by regions in which the dislocation density is lower by some orders of magnitude. Since the PSBs offer favorable sites for the initiation of fatigue cracks, the formation of the PSB wall structure is of great interest. Winter has proposed that PSBs form as the result of a transformation of the matrix structure to a regular wall structure, and that the instability occurs among the broad dipoles near the center of a vein rather than in the hard shell surounding the vein as argued by Kulmann-Wilsdorf.

Preparation of Electron Transparent Metal-Matrix Composites

1968 ◽  
Vol 26 ◽  
pp. 334-335 ◽  
Author(s):  
M. R. Pinnel ◽  
A. Lawley
Keyword(s):  
Stainless Steel ◽  
Load Transfer ◽  
Volume Fraction ◽  
Steel Wire ◽  
Initial Step ◽  
Interfacial Region ◽  
Matrix Composites ◽  
Specific Test ◽  
The Matrix ◽  
The One

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.

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