bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Characteristics of Zn-22% Al and Al-3% Mg Alloys Processed to High Strains by ECAP
Authors: Kumar Praveen , Langdon Terence G.
Published: December 2010

A processing route enhancing the strength of a metallic material usually leads to a decrease in the ductility. Therefore, a mechanical processing technique improving the ductility as well as the strength of a structural material is of significant importance. The present study employs equal-channel angular pressing to impart high strains up to ~24 and ~8, via route BC, in Zn-22% Al and Al-3% Mg alloys, respectively. Tensile specimens, machined from the central region of the processed materials, were tested at room temperature between strain rates of 10-3 and 1 s-1. The Zn-22% Al did not show the presence of a critical strain above which high ductility-high strength could be simultaneously achieved at any strain rate. However, Al-3% Mg processed through 8 passes of ECAP showed a transition to a high strength-high ductility region at high strain rates. The occurrence of high strength and high ductility in Al-3% Mg after processing to very high strains is probably due to the transition from the heavily deformed and heterogeneous microstructure present at the lower strains when processing by ECAP to the more homogeneous structures that develop after larger numbers of passes in ECAP. The absence of a transition strain in Zn-22% Al is attributed to its low melting temperature so that even at room temperature (~0.54Tm where Tm is the melting temperature) it shows diffusion-controlled high temperature deformation behavior.
Strengthening and Toughening Effect on Tungsten Subjected to Multiple ECAP
Authors: Yuan Hao , Zhang Yue , Ganeev Artur V. , Wang Jing Tao , Alexandrov Igor V.
Published: December 2010

This paper presents the research results of the grain refining effect on the ductile-to- brittle transition temperature (DBTT) of commercial purity tungsten. The as-received tungsten was subjected to eight passes of equal-channel angular pressing (ECAP) at decreasing temperatures from 1300 to 1150 °C. According to optical and TEM microscopy the average grain size was refined considerably from ~80 μm to ~1 μm. The mechanical tensile tests, carried out at various temperatures for the tungsten samples, showed that DBTT decreased approximately 80 °C as a result of microstructure refinement by ECAP, at the same time the strength also increased 50-100 % by grain refinement. SEM observation of the fractures confirmed the mechanical testing results.
Microstructure and Mechanical Properties of Mg-3Y Binary Alloy Processed by Cyclic Extrusion and Compression
Authors: Liu Xin Tao , Liu Man Ping , Wang Qu Dong , Guo Wei , Yin Dong Di
Published: December 2010

Mg-3wt.%Y alloys were processed by cyclic extrusion and compression (CEC) up to 7 passes at different temperatures from 375 to 450 °C, respectively. The microstructure was effectively refined and the mean grain size was decreased from 800 μm to 3–15 μm. Tensile and compressive tests were performed at room temperature at an initial strain rate of 1.11 × 10-3 s-1. The experimental results show that after 7-pass CEC processing the tensile yield strength and elongation-to-failure of Mg-3Y alloy increased simultaneously. Furthermore, the strength differential effect (SDE) of tension-compression of the alloy was weakened, especially the SDE value was only 3.3% when processed at 400 °C.
Investigation on Three-Dimensional Microstructures and Tensile Properties of Pure Iron during Equal-Channel Angular Pressing
Authors: Yang Gang , Yang Mu Xin , Liu Zheng Dong , Wang Chang , Huang Chong Xiang
Published: December 2010

Commercial pure iron billets having diameter of 60 mm and length of 180 mm were subjected to equal channel angular pressing (ECAP) at 350 °C for 1-4 passes via route BC. Microstructural evolutions on three planes (X, Y, Z planes) were characterized by optical microscopy and transmission electron microscopy (TEM). It was found that after four passes an ultrafine microstructure could be formed on the X plane, but a band structure remained on the Z plane. Accordingly, the mechanical properties exhibited apparent dependence on the orientations. The strength in the X and Y directions was higher than that in the Z direction. The microstructural refinement and mechanical properties were discussed in terms of experimental results.
Effect of Impurities on the Microstructure of HPT Deformed Nickel
Authors: Rathmayr Georg B. , Pippan Reinhard
Published: December 2010

Basic research considering the minimum achievable grain size of severe plastic deformation (SPD) materials is often performed with high purity metals. However, a literature study reveals large discrepancies in the microstructural size of high purity nickel processed by SPD. The focus of this work is the influence of small impurity concentrations on the resulting saturation microstructure. The microstructure of SPD nickel was systematically investigated using different purities ranging from 99.79 wt% up to 99.99 wt%. The materials were deformed by high pressure torsion (HPT) at different temperatures from liquid nitrogen temperature (-196°C) up to 400°C. It was found that carbon concentration is the governing element in achieving the finest microstructures and the highest strength. Therefore, further experiments with well defined carbon doped samples were performed. By changing the carbon content from 0.008 wt% up to 0.06 wt% tensile strength in the saturation regime increases by more than 700 MPa. It will be shown that even small variations (<0.01 wt%) lead to significant changes in ductility and tensile strength values.
Optimization of Tensile Strength and Ductility of Grade 2 Ti, Conditioned by Severe Plastic Deformation
Authors: de A. Mendes Filho A.A. , Sordi Vitor Luiz , Ferrante Maurizio
Published: December 2010

Among the materials employed for orthopedic implants, Ti-6Al-4V is definitely the best choice due to its excellent properties. However, a more intense use is hindered by high cost and the presence of harmful elements, viz. Al and V. A solution can be found in commercially pure Ti, provided its tensile and fatigue properties can be upgraded by some process of Severe Plastic Deformation. In the present work, Grade 2 Ti was submitted to up to four Equal Channel Angular Pressing passes, followed by cold rolling (30 70 and 90% reduction ratio) Hardness and tensile properties were determined, paying attention to the work hardening behavior. Results show that Severe Plastic Deformation gives a 442 MPa increase over the yield strength of annealed Grade 2 Ti (originally 337 MPa), while elongation reached 21%. Best results were obtained with four passes followed by 70% cold rolling reduction. Finally, the microstructural stability was assessed by hardness measurements.
Influence of Strain Reversals during High Pressure Torsion Process on Strengthening in Al-Cu-Mg(-Li) Alloy
Authors: Zhang Jiu Wen , Starink Marco J. , Gao Nong , Zhou Wen Long
Published: December 2010

The strengthening of AlCuMg(Li) alloys subjected to high pressure torsion (HPT) deformation with strain reversals was studied by microhardness (Hv) tests and differential scanning calorimetry (DSC). It was found that the strengthening is lower for both cyclic HPT (c-HPT) and single reversal HPT (sr-HPT) as compared to monotonic HPT (m-HPT). The DSC results demonstrate that |HPT influences S phase precipitation. With increasing strain, the maximum heat flow (height of the S peak) and the heat content of S formation peaks increases. There is a larger S heat content reaction in the periphery of HPT processed disks compared with those in the centre. Strain reversal also has a significant influence on the S precipitation. The strengthening during HPT deformation is discussed in terms of the density of statistically stored and geometrically necessary dislocations.
Finite Element Simulation of Effects of Mould Angle and Friction on ECAP for AZ80 Magnesium Alloy
Authors: Cai Gang Yi , Huang Xiao Ting , Zhang Shi Xing
Published: December 2010

Finite element simulation of the effects of mould angle and friction condition on the equal channel angular pressing (ECAP) for AZ80 magnesium alloy were investigated by using DEFORM-3D program. The results show that the curve of load-displacement was divided into several stages including rapid increasing stage, load fluctuation, rapid increasing stage, steady stage and rapid drop stage. Firstly, when the angle decreased from 150°to 90°, the maximum load increased, and the same as energy consuming. In addition, the average effective strain increased with the decreasing of mould angle after single extrusion, while the degree of effective strain uniformity of the sample decreased and keep greater strain grads between inner and surface part. Secondly, the work load ascended with the increasing of the friction coefficient from 0 to 0.3, and one part of load overcome the friction and the other part is used for deformation of the sample. With the increment of friction coefficient, the average effective strain keeps steady value, while the degree of effective strain uniformity of the sample decreased. As mentioned above, large angle mould and low coefficient of friction should be adopted during ECAP deformation for AZ80 magnesium alloy.
Mechanical Properties of an Al-5.4%Mg-0.5%Mn-0.1%Zr Alloy Subjected to ECAP and Rolling
Authors: Malopheyev Sergey , Kipelova Alla , Nikulin Ilya , Kaibyshev Rustam
Published: December 2010

Superplasticity and microstructural evolution of a commercial Al-5.4%Mg-0.5%Mn-0.1%Zr alloy subjected to severe plastic deformation through equal-channel angular pressing (ECAP) and subsequent rolling was studied in tension at strain rates ranging from 1.4×10-4 to 5.6×10-2 s-1 in the temperature interval 400-550°C. The alloy had an unrecrystallized microstructure with an average crystallite size less than 5 m. The alloy exhibited the yield strength of ~370 MPa, ultimate strength of ~450 MPa and elongation-to-failure of ~15% at ambient temperature. In spite of small crystallite size the alloy shows moderate superplastic properties. The highest elongation-to-failures of ~450% appeared at a temperature of ~500°C and an initial strain rate of ~1.4×10-3 s-1, where the strain rate sensitivity coefficient, m, is of about 0.57. The relationship between superplastic ductilities and microstructure is discussed.
Distribution of Mechanical Properties by Volume in Titanium Billets Processed by Twist Extrusion
Authors: Reshetov Alexey , Korshunov Alexander , Smolyakov A. , Beygelzimer Yan , Varyukhin Viktor , Kaganova Irina , Morozov A.
Published: December 2010

The influence of multipass processing by Twist Extrusion (TE) on distribution of mechanical properties by volume in commercially pure (CP) titanium billets is investigated. Experiments show that the mechanical properties are almost homogeneous in the billet cross-section already after the second pass of TE. This can be explained by mixing effect and saturation of properties as well. Warm TE leads to the formation of high strength properties in combination with high plasticity. Ultimate and yield stresses of the billet processed by two cycles of TE increased, in comparison with initial state, by 30% and 60% respectively. The value of the reduction in area remained at the initial value. This fact is indicating a high technological plasticity of the material, i.e. its ability for further shaping by metal forming methods.
Mechanical Spectroscopy of Ultrafine Grained Copper
Authors: Golovin Igor S. , Estrin Yuri
Published: December 2010

Temperature and amplitude dependent internal friction (TDIF and ADIF) in ultrafine-grained copper (99.95% Cu) processed by 1, 4, or 8 passes of equal channel angular pressing (route BC) and then subjected to annealing was investigated by means of mechanical spectroscopy. A dynamical mechanical analyzer DMA Q800 was used. The tests covered the temperature range from -100 to 550 °C, the strain amplitude range from 10-6 to 10-3, and the frequency range from 0.05 to 100 Hz. Two internal friction peaks were observed. They were explained by structural relaxation due to the recrystallisation process and by thermally activated grain boundary relaxation with a broad distribution of relaxation times. Increased amplitude dependent damping in ultrafine-grained copper is believed to be associated with a dislocation mechanism, rather than a grain boundary mechanism.
Flow Behaviour of Commercial Purity Titanium Subjected to Equal Channel Angular Pressing
Authors: Kumar G.V. Preetham , Uday Chakkingal
Published: December 2010

Commercial purity Ti was subjected to equal channel angular pressing (ECAP) for up to three passes at 400oC using a die with die angle of 120o. Compression testing of the ECAP specimens was carried out to determine the subsequent flow behavior. Two types of compression test specimen orientations, one parallel to the axis of ECAP and the other at 45o to the axis of the ECAP, were prepared from the specimens subjected to ECAP. Anisotropy in flow behaviour (as indicated by values of strength co-efficient, K and strain hardening exponent, n) was observed. The strain hardening rates were also calculated from the experimentally determined flow curves for the specimens tested in compression in the two orientations. The results have been interpreted in terms of the strain path change parameter between the two deformation steps (ECAP and compression). Strain hardening behaviour and microstructure evolution is discussed in terms of strain path change parameter. Specimens compressed in the direction parallel to the ECAP direction had lower strain hardening exponents while exhibiting higher initial flow stresses. The strain hardening rates were lower for specimens compressed at 45o to the ECAP direction compared to specimens compressed parallel to the ECAP direction.
The Dynamic Behavior of Ultra-Fine-Grained Copper Fabricated by Equal Channel Angular Pressing
Authors: Dong Yue Cheng , Alexandrov Igor V. , Wang Jing Tao
Published: December 2010

The high-strain-rate response of ultra-fine-grained (UFG) copper fabricated by equal channel angular pressing (ECAP) has been characterized by Split Hopkinson Pressure Bar (SHPB) test and quasi-static compression test has also been performed for comparison here. In the result of quasi-static tests a maximum yield stress equal to 432 MPa has been reached, at the same time the corresponding value turned out to be 995 MPa after a dynamic loading with the strain rate equal to 1700 s-1. It has been demonstrated that the strain rate sensitivity coefficient (m) has enhanced from 0.026 (coarse-grained copper) to 0.037 (UFG copper). Microstructure has indicated a high dislocation density and deformation twins inside the grains formed after a high-strain-rate deformation, which resulted in a high flow stress. The occurrence of a dynamic recrystallization has also been observed in the UFG copper subjected to high-strain-rate deformation. This has become apparent as an accelerated thermal softening and inherent instability typical for the UFG structure. Absence of adiabatic shear bands pointed out that UFG copper can be subjected to a dynamic impact without any fracture.
Application of High-Pressure Sliding for Grain Refinement of Al and Mg Alloys
Authors: Tazoe Kiyonari , Honda Shuji , Horita Z.
Published: December 2010

An earlier study showed that high-pressure sliding (HPS) is effective for grain refinement of pure Al in a rectangular sheet form using the principle of high-pressure torsion. In this study, the HPS is applied for grain refinement of an Al-3%Mg-0.2%Sc alloy and an AZ61 Mg alloy. HPS was conducted under a pressure of 1 GPa with sliding distances of 10 to 30 mm at room temperature for the Al alloy and at 473 K for the Mg alloy The average grain size is ~300 nm for both the Al and Mg alloys, respectively. Tensile tests showed that a superplastic elongation of ~1500% is achieved in the Al-3%Mg-0.2%Sc alloy at 573 K with an initial strain rate of 3.3x10-3 s-1 and of ~600% in the AZ61 alloy at 573 K with an initial strain rate of 1x10-3 s-1.
Optimization of Strength and Ductility in Ultra-Fine 304 Stainless Steel after Equal-Channel Angular Processing
Authors: Zheng Z.J. , Gao Yan , Gui Y. , Zhu M.
Published: December 2010

The microstructure and mechanical properties of 304 stainless steel were investigated which was subjected to equal channel angular pressing (ECAP). Tensile strength, elongation, Vickers hardness of as-ECAPed and annealed ECAPed 304 stainless steel were systematically measured and compared and microstructure evolution during ECAP and ECAP+annealing was observed by OM and TEM. It was found that with the increasing of ECAP passes, the grain size of stainless steel was effectively refined to nanoscale, such as about 50 nm after 8 ECAP-passes. In addition, the dislocation density in ECAPed samplel increased greatly, consequently, the tensile strength and hardness of ECAPed 304 stainless steel increased and elongation decreased remarkably. After annealing at 600°C for 10 min，the ductility of ECAPed stainless steel was improved greatly while grains did not have obvious growth, and strength did not change much. The above results showed that the optimization of strength and ductility in ultra-fined 304 stainless steel can be achieved by appropriate ECAP plus annealing processes.
Effect of ECAP on Microstructure and Mechanical Properties of an Al-Mg-Sc Alloy
Authors: Mogucheva Anna , Kaibyshev Rustam
Published: December 2010

An Al-4.57%Mg–0.2%Sc was subjected to equal channel angular pressing up to fixed true strains of 1, 2, 4, 8 and 12 at a temperature of 300oC. It was shown that extensive grain refinement occurs in this alloy through continuous dynamic recrystallization. As a result, ECAP can provide the formation of subgrain structure, partially recrystallized structure and fully recrystallized structure. The type of structure evolved is dependent on strain imposed. At ε2, the formation of three-dimensional arrays of low-angle boundaries takes place. Next, in the strain interval from 4 to 8 these low-angle boundaries gradually convert into high-angle boundaries. At ε12, fully recrystallized structure is evolved. Yield stress and ultimate strength gradually increases with increasing strain. Mechanisms of strengthening are discussed.
Effect of ECAP on Mechanical Properties of an Al-Cu-Mg-Ag-Sc Alloy
Authors: Gazizov Marat , Telesov Viktor , Zakharov Valerij V. , Kaibyshev Rustam
Published: December 2010

Effect of thermomechanical processing including equal-channel angular pressing (ECAP), solution treatment, water quenching and artificial aging on microstructure and mechanical properties of an Al-Cui-Mg-Ag-Sc alloy was examined. It was shown that ECAP provides extensive grain refinement. However, extensive grain growth occurs under subsequent solution treatment resulting in coarse grained structure. It was showed that ECAP following water quenching provides a minor increase in strength of the alloy. No effect of ECAP on the precipitation sequence under ageing was found. -phase precipitating under ageing condition is in dominant. As a result, the alloy exhibits high yield stress up to a temperature of 175oC. Conditions for attaining increased strength in the alloy by ECAP processing are discussed.
Hot Workability of Ultrafine-Grained Aluminum Alloy Produced by Severe Plastic Deformation of Al6063 Powder and Consolidation
Authors: Asgharzadeh Hamed , Simchi Abdolreza , Kim Hyoung Seop
Published: December 2010

Al6063 powder was subjected to severe plastic deformation via high-energy mechanical milling to prepare ultrafine-grained (UFG) aluminium alloy. Uniaxial compression test at various temperatures between 300 and 450 °C and strain rates between 0.01 and 1 s-1 was carried out to evaluate hot workability of the material. Microstructural studies were performed by EBSD and TEM. The average activation energy and strain rate sensitivity of the hot deformation process were determined to be 280 kJ mol-1 and 0.05, respectively. The deformation temperature and applied strain rate significantly affected the grain structure of UFG Al alloy. A finer grain structure was obtained at lower temperatures and higher strain rates. The formation of highly misoriented and equiaxed grains also revealed that dynamic recrystallization occurred upon hot deformation. Furthermore, elongated grains with high dislocation density were observed that disclosed partial dynamic recrystallization of the aluminum matrix.
Magnetic Micro Swimming Mechanism and Visualization of the Surface Flow Induced by the Mechanism Propulsion
Authors: Sudo Seiichi , Hoshika Kyohei , Funyu Kyohei , Yano Tetsuya
Published: December 2010

The micro magnetic swimming mechanism was produced for trial purposes based on the swimming analysis of copepods in the beginning. The magnetic mechanism composed of a permanent magnet and polyethyleneterephthalate film fin swims by the alternating magnetic field. Frequency characteristics of the swimming mechanism were examined, and surface flow fields induced by the robot propulsion were analyzed by visualization method. The swimming properties of micro magnetic mechanism were revealed experimentally.
Ultrasonic Investigation of the Effect of Volume Fraction on the Clustering Structures of Magneto-Rheological Fluids
Authors: Bramantya M.A. , Takuma H. , Kuroiwa J. , Sawada T.
Published: December 2010

The rheological response of magnetorheological fluid (MRF) results from the polarization induced in the suspended particles by application of an external magnetic field. Characteristics of an MRF depend on the volume faction, that is the percentage of magnetic particles in the carrier liquid. We propose a qualitative investigation of these volume fraction effects by measuring properties of ultrasonic wave propagation velocity in MRFs having various volume fractions. The ultrasonic wave propagation velocity changes under the effect of an external magnetic field as a result of arrangement of clusters along the direction of the field in the MRF.
Optimal Design of a Double-Sided Slotted Iron Core Type PMLSM with Manufacturing Considerations
Authors: Zhu Y.W. , Kim D.S. , Kooa D.H. , Cho Y.H.
Published: December 2010

This paper investigates an optimal design of a double-sided slotted iron core type permanent magnet linear synchronous motor (PMLSM) using for ropeless elevator system. To obtain the optimal structure, the combination of response surface methodology (RSM) and two dimensional (2D) finite element analysis (FEA), which can solve the problem effectively without much time consuming, is utilized to investigate the PMLSM characteristics. Moreover, the detent force is more detailed analyzed with the manufacturing consideration. In final some numerical calculation results are reported to validate the applicability of this double-sided slotted iron core type PMLSM in ropeless elevator system. Introduction
Investigation of the Impact of the Operational Temperature on the Performance of a Surface Permanent Magnet Motor
Authors: Beniakar Minos E. , Kefalas Themistoklis D. , Kladas Antonios G.
Published: December 2010

This paper investigates the impact of different operational temperatures on the performance of a surface permanent magnet (SPM) machine with neodymium-iron-boron (NdFeB) magnets for electric drive applications. The field distribution of the machine for various temperatures is depicted and a comparison of the field distribution in the air gap and the machine output characteristics is performed. On a second step the effect of rotor skew is investigated.
Coupled Field and Circuit Model Analysis of Permanent Magnet Synchronous Machine for Direct Torque Control Optimization
Authors: Tsampouris Evangelos M. , Patsios Charalampos , Chaniotis Antonios , Kladas Antonios G. , Prousalidis John
Published: December 2010

The pulsating torque of a permanent magnet motor has detrimental effects on the motor operation, resulting in speed perturbation, positioning error, vibration, and noise. Several efforts of countering the torque ripple focus on magnet pole shape optimization procedures while other efforts apply sophisticated modifications of control algorithms. In this paper a coupled field and circuit model of a permanent magnet synchronous machine (PMSM) is introduced in order to reduce the effects of pulsating torque. The model comprises of a 2D finite element model for detailed computation of the machine field distribution coupled with an external equivalent circuit for macroscopic parameter evaluation. Model results are then integrated in a direct torque control algorithm for the minimization of torque ripple in a PM machine prototype.
Stability of Toroidal SMES Using YBCO Tapes for Simultaneous Quench of a few Coils
Authors: Noguchi So , Kim Seok Beom
Published: December 2010

We have investigated the stability of 2.0 GJ toroidal HTS-SMES, which consists of 90 element coils wound from YBCO tape. If one or more element coils are quenched, the storage energy reduces due to change of the magnetic field distribution. A series of quench for some element coils may occur, when the energy of the quenched coil cannot be consumed adequately. The simultaneous quench of some element coil may cause the system down. Therefore, it is necessary to investigate the simultaneous quench properties.
Improvements of Feedback Control Algorism in Two-Dimensional Vector Magnetic Property Measurements
Authors: Todaka Takashi , Sato Takeru , Ishikawa Seiji , Maeda Yoshitaka , Enokizono Masato
Published: December 2010

This paper presents comparison of feedback control algorisms of magnetic flux conditions in two-dimensional vector magnetic property measurements under high magnetic field over 1.6 T. In order to develop a fast measurement algorism, several PID feedback control methods were tested. The results show that the proportion-derivative precedence type (I-PD) control is suitable for reduction of measurement times in vector magnetic property measurements.
Optimal Design of the Electro-Magnetic Actuator for High Voltage Circuit Breaker
Authors: Kang Jong Ho , Jung Hyun Kyo
Published: December 2010

The motor-spring and hydraulic actuators have long constituted as a mechanism for HGCB, regardless of the fatal disadvantages of the malfunction. Although many attempts have been made to cope with them, there is no alternative to replace this mechanism. This paper presents a new type of the electric actuator, electro-magnetic force driving actuator (EMFA) for high-voltage gas circuit breaker (HGCB) and describes the principle of the optimal design. Auto-Tuning Niching Genetic Algorithm combined with deterministic method (Pattern Search Method) is developed to reduce the number of object function calls and used for the optimal design. Fabrication and experiment were performed in order to prove the applicability for HGCB overall class. In comparing the experiment with simulated data, it is confirmed that analysis of the dynamic characteristics of EMFA is appropriate for design.
Thermal Analysis of Canned Induction Motor for Coolant Pump Considering the Eddy Current Loss in Cans
Authors: Li Jian , Song Jung Tae , Cho Yun Hyun
Published: December 2010

This paper describes thermal analysis of canned induction motor for coolant pump considering eddy current loss. The electromagnetic field of a canned motor was analyzed by using the time-step finite element method, and the eddy loss was obtained. Equivalent circuit considering can loss was developed and the equitation to calculate can loss was derived from theory of conventional motor. Using the loss from electromagnetic analysis as heat source of temperature field, thermal analysis was conducted by three dimensional finite element analyses. The simulation results show good agreement with experiment data, which indicates that this method has good accuracy and reliability for dealing with thermal behavior of canned motor.
The Numerical Calculation of HV Fuses Pre-Arcing Time in the Case of Transversal Adiabatic Proces
Authors: Giurgiu Valer , Hantila Ioan Florea , Maricaru Mihai , Stanculescu Marilena
Published: December 2010

Unlike the protection systems with electromechanical action protection, the fuses have the advantage of sure protection. Designing fuses requires a high accuracy for determining the current field density and the temperatures from the fuse-elements, till they melt. In order to have zero divergent of the current density the paper employs a FEM procedure in which the electrical vector potential is implied. Special shape functions are used for holes in the case of multiply connected structure. The electric problem is coupled with thermal field one.
Study of the Magnetic Anisotropy of the Grain Oriented (GO) and Non-Oriented (NO) Silicon Iron Materials
Authors: Păltânea Veronika , Paltanea Gheorghe
Published: December 2010

In this paper it is presented a study of the magnetic anisotropy of non-oriented and grain oriented Fe-Si strips with the surface area of 280 x 30 mm2. The measurements were performed with a unidirectional single strip tester on Fe-Si strips cut at angles of 0, 15, 30, 45, 60, 75, 90 with the rolling direction. For the representation of the magnetic field strength at constant magnetic flux density it was used a program that interpolated the experimental results. It was determined the hard and the easy axis of the materials and the influence of the frequency on the anisotropy of the materials.
On the Magnetic and Magnetoelastic Uniformity Measurements on Fe78Si7B15 Amorphous Ribbons and Wires
Authors: Mamalis A.G. , Hristoforou Evangelos
Published: December 2010

In this paper we present new results on magnetic and magnetoelastic uniformity measurements on Fe78Si7B15 amorphous ribbons and wires. The measurements are performed using an automatic instrumentation device based on the magnetostrictive delay line technique, with the ability to determine the B(H) and (H) functions along the length of a ribbon with parametric control of field and frequency. According to these results, it has been determined that magnetic and magnetoelastic uniformity functions are subject to the history of the under test samples.
Magnetoelastic Resonance in Zero-Mean Magnetostrictive Media
Authors: Ignatchenko V.A. , Polukhin D.S.
Published: December 2010

The interaction between two wave fields of different nature that are caused by rms fluctuations of the coupling parameter between these fields in media with zero-mean coupling parameter is considered. Taking into consideration the multiple scattering processes of waves on the inhomogeneities leads to the results considerably different from those that have been obtained for the same situation in the Bourret approximation earlier [4,5]. Instead of the degeneration removal of frequencies in the wave spectrum and the appearance of two resonance peaks in the dynamic susceptibility at the intersection of the initial dispersion laws, the sharp broadening of the self-mode peak has to be observed. The consideration is done by the example of magnetoelastic waves in zero-mean magnetostrictive media.
The Magnetic Phase Transitions and Magnetocaloric Effect in the Ho(Co1-XAlx)2 and Tb(Co1-XAlx)2 Compounds
Authors: Nikitin S.A. , Tskhadadze G.A. , Ovchenkova I.A. , Zhukova D.A. , Ivanova T.I.
Published: December 2010

Direct measurements of the magnetocaloric effect (MCE) and magnetization have been conducted for the R(Co1-xAlx)2 (R = Tb, Ho) compounds. It was found that the small substitutions of Co by nonmagnetic Al lead to an increase both of the magnetic ordering temperature and the value of MCE. The following increase in Al content decreases the Curie temperature and the value of MCE. The analyses of the MCE effect is conducted considering the ferrimagnetic structure and the itinerant nature of these compounds.
Temperature Behaviour of Magnetic Domain Structure in RE-3d Intermetallics with Spin-Reorientation Transitions
Authors: Subkova A.V. , Zeziulina P.A. , Koshkid’ko Y.S. , Simonov V.V. , Skokov Konstantin , Pastushenkov Yury G.
Published: December 2010

Characteristics of the temperature transformation of magnetic domain structure (DS) during different spin reorientation transitions (SRT) are analyzed on the basis of DS investigations of R2Fe14B, RFe11Ti, RCo5, R2Fe17 single crystals (R = Nd, Gd, Tb, Dy, Ho, Er) in the temperature interval of 4.2 - 400 K.
Spin Reorientation Transition in Nanocrystalline (Pr,Sm)Fe8Ga3C Alloys
Authors: Popov A.G. , Gorbunov D.I. , Ivanova G.V. , Makarova G.M. , Korolyov A.V.
Published: December 2010

Spin-reorientation transitions in intermetallic (Pr1-xSmx)Fe8Ga3C compounds with the tetragonal BaCd11-type structure have been investigated. The magnetic phase diagram has been proposed for these compounds based on magnetic and X-Ray diffraction studies using their nanocrystalline ribbons and powders aligned in a magnetic field. In the concentration range 0 ≤ x ≤ 0.4 the compounds exhibit an «easy-plane» anisotropy at all temperatures of the magnetically ordered state. The magnetic anisotropy of the compounds with 0.5 ≤ x ≤ 1 is of the «easy-cone» type. The SmFe8Ga3C compound with the highest Sm content is a uniaxial ferromagnet with no indications of a spin-reorientation transition below its Curie temperature.
The Induced Anisotropy and its Influence on Absorption of the NMR and Domain Structure of Со-Р Amorphous Films
Authors: Chzhan A. V. , Patrin G.S. , Kiparisov S.Y. , Seredkin V. A. , Maltsev V.K. , Krayukhin I.N.
Published: December 2010

The results of experimental research into magnetic properties of amorphous Co-P films obtained by chemical sedimentation on various intermediate layers have been represented. The nuclear magnetic resonance (NMR) spectra of films sedimentated on intermediate layers of Pd crystal and amorphous NiP compound have been measured .The features of formation of domain structures and magnetization processes in the presence and absence of the induced anisotropy have been described.
Magnetic Properties of Intercalated Zinc Hexacyanoferrate (II)
Authors: Denisova Tatiana A. , Maksimova Lidia G. , Kellerman Dina G. , Melkozerova M.A. , Zabolotskaya Elena V. , Mitrofanov Valentin Yakovlevich , Dorogina G.A.
Published: December 2010

The results of magnetic behavior study of nickel ions, which were introduced into Zn2Fe(CN)6∙5.5H2O with channel structure, are presented. It was shown that nickel cations replace a part of Zn2+ ions or locate in the channels of lattice via the molecular mechanism sorption. It is shown that the magnetic moments μNi of the sorption products strongly depend on the content of Ni2+ ions. The values of μNi of the samples with Ni/Fe(CN)6=2.26 and 2.86 are great ~ 3.9 and 4.4 μB respectively and close to the value typical of free Ni2+ ions μ =4.47μB.
Antiferromagnetic Conic Refraction of Sound in Hematite
Authors: Migachev S.A. , Sadykov M.F. , Shakirzyanov M.M. , Ivanov D.A.
Published: December 2010

In a trigonal easy-plane -Fe2O3 antiferromagnet magnetic-field-dependent conic refraction due to the renormalization of the coefficients of elasticity effective magnetoelastic interaction is experimentally found in addition to the conventional internal conic refraction of the transverse elastic waves propagating along the trigonal C3 axis. It is shown that the deflection angle () of the energy flow from the C3 axis upon the internal conic refraction does not depend on the value of the magnetic field applied in the basis plane (HC3) and is a constant value determined by the correlation of the C14 and C44 coefficients of elasticity. The deflection angle of the energy flow upon the antiferromagnetic conic refraction () increases with increase in the field and tends to the  value at large H values. The obtained results agree well with the theory of this phenomenon in antiferromagnets and support its conclusions.
Magnetic Anisotropy of Helical and Collinear Magnets R2Fe17-XMnx
Authors: Kuchin Anatoly G.
Published: December 2010

Magnetic anisotropy of the easy-plane type in the R2Fe17-хMnx systems with R = Ce and Lu weakens upon substitution of Mn for Fe. Temperature dependence of the first magnetic anisotropy constant (K1) of the R2Fe17-xMnx systems is described rather well in the single-ion model of magnetic anisotropy. However, in the case of the Ce2Fe17-хMnx helical ferromagnets the experimental variation of K1 is somewhat slower than that calculated by the third power of the spontaneous magnetization, in contrast to the Lu2Fe17-хMnx collinear ferromagnets, where K1 decreases slightly faster with increasing temperature as compared with this fit.
Dynamic Chains of Spiral Magnetic Domains
Authors: Pashko Anna G. , Bareev R.G. , Osadchenko V. , Lobasheva N. , Kandaurova G.S.
Published: December 2010

In this paper we present the results of investigation of spiral dynamic domains of a highly anisotropic iron garnet film with a perpendicular anisotropy in magnetic field with a constant dimensional gradient. The experiment showed how the presence of gradient of constant field affects the main parameters of spiral dynamic domains – geometrical form, life time, amount of orbits.
Giant Magnetoresistance in Magnetic Nanostructures and Spintronic Devices
Authors: Lutsev L.V. , Stognij A.I. , Novitskii N.N. , Shulenkov A.S.
Published: December 2010

The injection magnetoresistance effect in SiO2(Co)/GaAs heterostructures, where SiO2(Co) is a granular SiO2 film containing Co nanoparticles, has been studied. This effect manifests itself in the avalanche breakdown mode and has extremely large values at room temperature due to the spin-dependent potential barrier. We consider application of the IMR effect and SiO2(Co)/GaAs heterostructures in spintronic devices – high sensitive magnetic sensors and field-effect transistors governed by applied magnetic field.
Mechanisms of Pinning of Domain Walls in Nanowires
Authors: Ivanov A.A. , Orlov V.A. , Podolsky N.N.
Published: December 2010

Analytical and numerical methods are used to study the process of motion of domain walls in an individual nanowire consisting of ferromagnetic crystallites with a chaotic crystallographic anisotropy. The influence of magnetostatic interaction on the motion is considered. The force profile of the domain wall pinning, caused by stochastic crystallographic anisotropy, is examined. The magnetization curve is analytically constructed and the coercive force is calculated. The Barkhausen jumps of domain walls are investigated. The result is verified by numerically modeling.
Self-Oscillations of Current Density upon Nonequilibrium Electronic Phase Transition in Nearly Magnetic FeSi
Authors: Volkov A.G. , Cherepanova A.N.
Published: December 2010

Within an sd-model involving a spin-fluctuation method, the behavior of strong-paramagnetic semiconductor FeSi in strong electrical field is numerically investigated. It is established that due to the self-heat phenomenon there exists a bi-stable state, and the (I-U)-characteristic is S-like in shape. It is shown that in the bistable area there arise current self-oscillations at a constant voltage.
Complementary Analysis of Epitaxial Fe (001) Films with Improved Electronic Transport and Magnetic Properties
Authors: Mikhailov G.M. , Fomin L.A. , Vinnichenko V.Yu. , Malikov I.V. , Chernikh A.V.
Published: December 2010

Complementary analysis of morphology, crystal structure, electronic transport, and magnetic properties is applied to optimize the epitaxial growth of Fe(001) films with the improved electronic transport and magnetic properties. It was found that the mean free path of residual electrons and coercive forces are correlated in the epitaxial single-crystal Fe(001) films grown under different temperatures and depend on the film morphology.
Magnetic and Dielectric Properties of Nanophase Lithium-Substituted Manganese-Zinc Ferrite
Authors: De Fazio E. , Bercoff P.G. , Jacobo Silvia E.
Published: December 2010

Nanocrystalline lithium-substituted manganese-zinc ferrites Li0.5xMn0.4Zn0.6-xFe2+0.5xO4 were prepared by the sol-gel autocombustion method. X-ray diffraction analysis (XRD) confirmed that samples are single-phase and that only a spinel phase is present. The saturation magnetization increases while the cell parameter of the cubic phase decreases with Li concentration. Magnetic permeability and dielectric permittivity of all samples were measured at room temperature as a function of frequency. Reflection loss calculations show that the prepared samples are good electromagnetic wave absorbers in microwave range. Li substitution plays an important role in changing the structural and magnetic properties of these MnZn ferrites.
Electronic Structure and Magnetic State of TiSe2 Doped with Cr by Means of Intercalation or Substitution of Ti
Authors: Shkvarin A.S. , Merentsov A.I. , Yarmoshenko Y.M. , Skorikov N.A. , Titov A.N.
Published: December 2010

Solid solutions 1T-CrxTi1-xSe2 (x = 0-0,83) were synthesized. Single crystals in the concentration range x = 0-0.69 were grown. Structure of these materials was studied on single- and polycrystalline samples. It was determined that chromium atoms substitute for titanium atoms in the TiSe2 host lattice. XPS measurements of the core levels together with the resonance valence band spectra of the 1T-CrxTi1-xSe2, as well as absorption spectra of Ti and Cr were performed. According to the experimental XAS data and multiplet atomic calculation, titanium and chromium atoms have oxidation numbers of +4 and +3, respectively. The local magnetic moment of about 3 eV is detected at Cr atoms. A transition into the spin glass state is observed. The modeling calculations of chromium local density of states were carried out. These results are in a good agreement with the experimental ones and suggest that 3d density of electronic states of chromium that substitutes for titanium in the host lattice is spin polarized and has a half-metallic character.
ESR Study of Novel Room-Temperature Ferromagnetic Semiconductors Pb1-X-YSnxCryTe
Authors: Zvereva E.A. , Savelieva O.A. , Ibragimov S. , Samokhvalov E. , Slynko E.I. , Slyn'ko V.E.
Published: December 2010

We report on the magnetic properties of novel diluted magnetic semiconductors Pb1 x ySnxCryTe revealing ferromagnetism at temperatures higher than room temperature. Depending on chromium concentration the Curie temperature varies in a wide range (150360 K) and effective magnetic moment achieves 1 B upon an increase of chromium doping level. Electron spin resonance (ESR) spectra in the paramagnetic phase were satisfactory approximated by a single Dysonian line. Effective g-factor tends to the saturation value g=2.080.01, while the linewidth passes through a minimum in the vicinity of magnetic ordering transition and then broadens with an increase of the temperature. In ferromagnetic phase the pronounced distortion and splitting of the ESR spectra into two lines occurs due to additional ferromagnetic contribution to absorption.
Frustrations and Phase Transitions in Ising Model on 2D Lattices
Authors: Kassan-Ogly Felix A. , Filippov B.N. , Men’shenin V.V. , Murtazaev Akai K. , Ramazanov M.K. , Badiev M.K.
Published: December 2010

The problem of frustrations and phase transition appearance or suppression is studied on the base of exact analytical solutions for maximum eigenvalue of Kramers-Wannier transfer matrix in the Ising model on a square lattice [1], a triangular and honeycomb lattices [2], and kagome lattice [3] with allowance for the interactions between nearest J is studied. We also studied these phenomena by the numerical “replica Monte Carlo method”, taking also into account the interactions between next-nearest neighbors J'.
Inhomogeneous Magnetic State above the Curie Temperature of the Doped Cobaltite La1-XSrxCoO3
Authors: Lazuta A.V. , Ryzhov V.A. , Kurbakov A.I. , Khavronin V.P. , Molkanov P.L. , Mukovskii Y.M. , Pestun A.E. , Privezentsev R.V.
Published: December 2010

Results of structural neutron diffraction study and data on the transport and magnetic properties (the linear and nonlinear (second and third order) susceptibilities) are reported for the La1-xSrxCoO3 (x = 0.18 and 0.2) polycrystals. The data on the linear and third-order susceptibilities show indications of a long - range ferromagnetic ordering with the Curie temperature (TC) about 180 K. Measurements of the second harmonic of the magnetization in the parallel ac and steady (H) magnetic fields (M2(H,T)) reveal the appearance of ferromagnetic clusters in a paramagnetic matrix below some temperature (T*) above TC. The characteristics of this clustered state and the stages of its temperature evolution are reliably determined since the non-ferromagnetic matrix affects weakly this state. It is found that a spontaneous nucleation of the ferromagnetic clusters occurs below T*, and their concentration increases sharply on cooling. Upon further decreasing temperature, the isolated clusters coalesce, leading to a percolative - type origination of a ferromagnetism. The M2(H,T) response of isolated clusters and its T-variation, including the onset of the coalescence, are very close to those found in the doped manganites, which supports an assumption on a common origin of the clustered state in these compounds.
Phase Diagram of Spin States and Magnetic Interactions in Isotope Substituted (Pr,Eu)0.7Ca0.3CoO3
Authors: Kalinov A.V. , Gorbenko O.Yu. , Taldenkov A.N. , Rohrkamp J. , Heyer O. , Jodlauk S. , Babushkina N.A. , Fisher L.M. , Kaul A.R. , Khomskii D.I. , Kugel K.I. , Lorenz T.
Published: December 2010

The magnetic/spin-state phase diagram of the (Pr1-yEuy)0.7Ca0.3CoO3 series was obtained on the basis of measurements of the specific heat, thermal expansion, magnetization and resistivity. The phase diagram reveals three different states depending on the static distortions (Eu content), the oxygen-isotope mass, and the temperature. The samples with the lower Eu concentrations are ferromagnetically ordered up to moderate temperatures (about 50 K),, most probably, due to the low-spin Co4+ – intermediate-spin Co3+ interaction of the double-exchange type. As the Eu doping increases, the Co3+ LS (S = 0) state becomes stabilized and the magnetic ordering of the Co4+ ions is suppressed up to temperatures well below 5 K, resulting in a low-temperature anomaly in Cp. At higher temperatures, we observe a first-order spin-state transition from the LS to the IS state of Co3+, which is accompanied by a decrease in the electrical resistivity, an increase in the magnetization, and a strong lattice expansion.
Magnetic State of Y3Fe5-XScxO12 Garnets
Authors: Chukalkin Y.G. , Teplykh A.E.
Published: December 2010

Ferrogarnets of the system {Y3}[Fe2-xScx](Fe3)O12 were investigated by neutron diffraction and magnetic methods. Parameters of crystal structure were refined. It was found that deviations from a collinear ferrimagnetic structure emerged at x ~ 0.7. At high concentrations of Sc a growth of the high-field magnetic susceptibility and an abnormal temperature dependences of dynamic susceptibility typical of local angular spin structures were revealed. The fracture temperatures for the local angular structures were determined.
Spontaneous Magnetization and Antiferromagnetic Correlations in Low-Dimensional Quantum (S=1/2) Single Crystal LiCu2O2+Δ
Authors: Tishchenko E.A. , Omelyanovskii O.E. , Sadakov A.V. , Eshchenko D.G. , Bush A.A. , Kamenzev K.E.
Published: December 2010

The low temperature investigations of the magnetic properties of non-twinning LiCu2O2+δ crystals showed that a new spontaneous magnetization phase arises in the compound at temperatures less than T~150 K along with the basic long-range helimagnet phase at T<24 K. The increase of an extra oxygen Оδ concentration intensifies ferromagnetic response of this phase. We suggested a cluster model for the new phase as an antiferromagnet structure with a short-range order with the weak and hidden ferromagnetism on the basis of both the theoretical group analysis of the magnetic and crystal lattice symmetry and the analysis of the temperature, field, hysteresis and anisotropy properties of spontaneous magnetization.