Modeling the Magnetic Properties of Non-Oriented Electrical Steels Based on Microstructural Parameters

2011 ◽  
Vol 702-703 ◽  
pp. 734-737 ◽  
Author(s):  
Hadi Pirgazi ◽  
Roumen H. Petrov ◽  
Leo Kestens
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Chemical Composition ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Quantitative Model ◽  
Experimental Results ◽  
Pole Density ◽  
Electrical Steels ◽  
Magnetization Behavior

Magnetic properties of electrical steels such as magnetization behavior and electrical losses are mainly related to chemical composition, crystallographic orientation and microstructure. By now, several models have been proposed to empirically correlate magnetic properties and affecting parameters. A quantitative model based on physical understanding of the interaction between the magnetic field variables (e.g. domain structure) and local microstructural variables (e.g. grain orientation and misorientation, grain boundary plane inclination) is still missing. To obtain a better understanding of the interaction between grain boundaries and domain walls, the magnitude of free pole density at grain boundaries was taken into account. Experimental results from 3-dimentional EBSD experiments were employed to measure the grain boundary orientation for several samples with different chemical composition and grain size. The free pole density was calculated using the relative misorientation between adjacent grains, and was included in a model together with grain size, magnetocrystalline anisotropy energy and silicon equivalent. By comparison with the experimental results of the magnetic induction measured at low, medium and high magnetic fields, is shown that the magnetization behavior can be more accurately predicted when the above mentioned phenomena are taken into account.

Effect of Aging Treatment on the Microstructures and the Magnetic Properties of the Sintered Nd-Fe-B Magnet

2014 ◽  
Vol 886 ◽  
pp. 66-70
Author(s):  
Xiao Li Wang ◽  
Li Na Zhao ◽  
Cong Hui Si ◽  
Kai Hong Ding ◽  
Sheng Li Cui ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Grain Boundary ◽  
Coercive Force ◽  
Grain Boundaries ◽  
Magnetic Phase ◽  
Aging Treatment ◽  
Experimental Results ◽  
Main Phase ◽  
Boundary Phase ◽  
Two Stage

The effect of aging processes on the microstructures and the magnetic properties of the sintered Nd-Fe-B magnet was investigated. The experimental results showed that the grain boundaries of the magnet treated by the two-stage aging processes became clear,smooth and continuous. Meanwhile, the Nd-rich grain boundary phase was precipitated at the grain boundary of the main phase to form a distinct phase separated from the main magnetic phase. The changes of the grain boundary microstructures of the sintered Nd-Fe-B magnet caused significant increase of its intrinsic coercive force.

The Influence of Grain-Boundary Structural Disorder on the Magnetic Properties of Nanocrystalline Nickel

1993 ◽  
Vol 318 ◽  
Author(s):  
Barbara Szpunar ◽  
Uwe Erb ◽  
Karl T. Aust ◽  
Gino Palumbo ◽  
Laurent J. Lewis
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Magnetic Moment ◽  
Recent Observation ◽  
Extreme Case ◽  
Structural Disorder ◽  
Nanocrystalline Nickel ◽  
Electrodeposited Nickel

ABSTRACTThe influence of grain boundaries on the magnetic properties of nanocrystalline nickel, in particular the ∑ = 3 and ∑ = 5 special grain boundaries and the extreme case of a purely amorphous sample, has been investigated. Our calculations reveal that the magnetic moment is rather insensitive to the structural disorder varying by at most 15 %. These results correlate extremely well with the recent observation in electrodeposited nickel that the magnetic moment depends very little on grain size, down to about 10 nm.

Research on Effects of Mo Element on the Magnetic Properties of 1J79 Alloy

2010 ◽  
Vol 160-162 ◽  
pp. 1787-1790
Author(s):  
Jing Cao ◽  
Yong Feng Wang ◽  
Chun Xue Wei
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Crystal Growth ◽  
Saturation Magnetization ◽  
Electron Probe ◽  
Electric Arc ◽  
Experimental Results ◽  
Vibrating Sample Magnetometer ◽  
Electron Probe Microanalyzer ◽  
Mo Content

1J79 alloy was prepared by vacuum electric arc smelting．The crystal growth and the content of impurity was observed by electron probe microanalyzer，and magnetic properties were measured by vibrating sample magnetometer(VSM)．Experimental results show that inclusions in the alloy are fewer and fewer, composition becomes more uniform with the increases of the Mo content, and grain size also becomes larger and larger with the increases of Mo content, to reduce coercivity. The small amount of Mo addition is useful to improve the saturation magnetization and reduce coercivity．

Simulation of the interaction of plastic zone dislocations with the grain boundary at brittle-plastic transition temperatures in molybdenum

2021 ◽  
Vol 2021 (3) ◽  
pp. 77-85
Author(s):  
K. M. Borysovska ◽  
◽  
N. M. Marchenko ◽  
Yu. M. Podrezov ◽  
S. O. Firstov ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
Grain Boundary ◽  
Plastic Zone ◽  
Grain Boundaries ◽  
Crack Tip ◽  
Dynamics Simulation ◽  
Density Of Dislocations ◽  
Grain Sizes ◽  
Pile Up

The (DD) method was used to model the formation of the plastic zone of the top of the cracks in polycrystalline molybdenum. Special attention was paid to take into account the interaction of dislocations in the plastic zone with grain boundaries. Structural sensitivity of fracture toughness was analyzed under brittle-ductile condition. Simulations were performed for a range of grain sizes from 400 to 100 μm, at which a sudden increase in fracture toughness with a decrease of grain size was experimentally shown. We calculated the value of K1c taking into account the shielding action of dislocations. The position of all dislocations in the plastic zone at fracture moment was calculated. Based on these data, we obtained the dependences of dislocation density on the distance from the crack tip thereby confirming significant influence of the grain boundaries on plastic zone formation. At large grain sizes, when the plastic zone does not touch the boundary, the distribution of dislocations remained unchanged. As grains reduce their size to size of the plastic zone, they start formating a dislocation pile – up near the boundaries. Dislocations on plastic zone move slightly toward the crack tip, but the density of dislocations in the middle of the grain remains unchanged, and fracture toughness remains almost unchanged. Further reduction of the grain size leads to the Frank-Reed source activation on the grain boundary Forming dislocation pile-up of the neighbor grains. Its stress concentration acts on dislocations of the first grain and causes redistribution of plastic zone dislocations. If the reduction in grain size is not enough to form a strong pile-up, density of dislocations on plastic zone increases slightly and crack resistance increases a few percent. Further reduction of grains promotes strong pile-up, dislocations move to crack tip, and its density on plastic zone increases. Crack is shielded and fracture toughness increases sharply. The calculation showed that the fracture toughness jump is observed at grain sizes of 100—150 μm, in good agreement with the experiment. Keywords: dislocation dynamics simulation, molybdenum, fracture toughness, grain size, plastic zone, brittle-ductile transition.

Mechanical Behaviour of Nanocrystalline Copper Related to Grain-boundary Structure

2002 ◽  
Vol 727 ◽  
Author(s):  
Y. Champion ◽  
P. Langlois ◽  
S. Guérin-Mailly ◽  
C. Langlois ◽  
M. J. Hÿtch
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Structural Analysis ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Mechanical Behaviour ◽  
Tensile Testing ◽  
Metallic Nanostructures ◽  
Nanocrystalline Powders ◽  
Clear Understanding

AbstractUnderstanding the mechanical behaviour of metallic nanostructures is a key issue for their development. On the one hand, knowledge of the plastic behaviour at various temperatures is essential to control the synthesis, forming, and machining of such materials. Equally, a clear understanding of atomic and mesoscopic mechanisms, involving defects and their interactions, is essential for the control of ageing and functional properties. Regarding plastic deformation at room temperature, there is now evidence for unusual behaviour in nanostructured metals. In addition to high resistance and ductility, tensile testing reveals peculiar elasto-plastic deformation. Such behaviour was initially attributed to grain-boundary sliding. However, intergranular areas (including triple junctions) may possess special properties compared to their microcrystalline counterparts. For example, low activation energies have been measured for grain-boundary diffusion and it has been observed that grain-boundaries may act as dislocation sources and nucleation sites for deformation twinning.In this paper, we report on analysis on bulk copper nanostructures. Grain-boundaries are studied, by cross-correlating information from mechanical tensile testing and structural analysis, including X-ray diffraction (XRD) and transmission electron microscopy (TEM). Macroscopic bulk specimens (with grain size of about 80 nm) are prepared by powder metallurgy techniques, modified to fit to the special properties of nanocrystalline powders. Processing includes coldisostatic pressing, sintering and differential extrusion. The powders used (grain size of 40 nm) are synthesised by evaporation and cryo-condensation of a metallic vapour within liquid nitrogen. Results on mechanical testing and structural analysis will be reported. Emphasis will be placed on the structure of grain-boundaries (type of grain-boundary, grain-boundary thickness) studied by TEM and high resolution TEM image analysed using the geometric phase technique. The nanostructure was revealed to be consist in agglomerate of nano-size grains separated by low angle grain-boundaries. Agglomerates are themselves separerated by general high angle boundaries. These observations will then be related to the unusual mechanical true stress-true strain curves of the metallic nanostructures.

scholarly journals Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing

Solid Earth ◽  
2017 ◽  
Vol 8 (6) ◽  
pp. 1193-1209 ◽  
Author(s):  
James Gilgannon ◽  
Florian Fusseis ◽  
Luca Menegon ◽  
Klaus Regenauer-Lieb ◽  
Jim Buckman
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Finite Strain ◽  
Grain Boundary Sliding ◽  
Large Strains ◽  
Cavity Formation ◽  
Phase Mixing ◽  
Transient Phenomena ◽  
Boundary Sliding

Abstract. Establishing models for the formation of well-mixed polyphase domains in ultramylonites is difficult because the effects of large strains and thermo-hydro-chemo-mechanical feedbacks can obscure the transient phenomena that may be responsible for domain production. We use scanning electron microscopy and nanotomography to offer critical insights into how the microstructure of a highly deformed quartzo-feldspathic ultramylonite evolved. The dispersal of monomineralic quartz domains in the ultramylonite is interpreted to be the result of the emergence of synkinematic pores, called creep cavities. The cavities can be considered the product of two distinct mechanisms that formed hierarchically: Zener–Stroh cracking and viscous grain-boundary sliding. In initially thick and coherent quartz ribbons deforming by grain-size-insensitive creep, cavities were generated by the Zener–Stroh mechanism on grain boundaries aligned with the YZ plane of finite strain. The opening of creep cavities promoted the ingress of fluids to sites of low stress. The local addition of a fluid lowered the adhesion and cohesion of grain boundaries and promoted viscous grain-boundary sliding. With the increased contribution of viscous grain-boundary sliding, a second population of cavities formed to accommodate strain incompatibilities. Ultimately, the emergence of creep cavities is interpreted to be responsible for the transition of quartz domains from a grain-size-insensitive to a grain-size-sensitive rheology.

A Different View on Dynamic Recrystallization

2012 ◽  
Vol 715-716 ◽  
pp. 235-242 ◽  
Author(s):  
Günter Gottstein
Keyword(s):  
Grain Size ◽  
Steady State ◽  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Experimental Results ◽  
Critical Conditions ◽  
New Approach ◽  
Theoretical Predictions

A new approach to dynamic recrystallization (DRX) is introduced. It is based on the assumption that the critical conditions for DRX and the arrest of DRX grain boundaries are related to the development of mobile subboundaries. The theoretical predictions are compared to experimental results during incipient and steady-state DRX. The grain size sensitivity of the DRX grains establishes the desired link between deformation and DRX microstructure.

Improving magnetic properties of non-oriented electrical steels by controlling grain size prior to cold rolling

2019 ◽  
Vol 491 ◽  
pp. 165636 ◽  
Author(s):  
Ling-Zi An ◽  
Yin-ping Wang ◽  
Hong-Yu Song ◽  
Guo-Dong Wang ◽  
Hai-Tao Liu
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Cold Rolling ◽  
Electrical Steels

Texture and Microstructure Evolution during Box Annealing of a Non-Oriented-Grain Electrical Steel

2011 ◽  
Vol 702-703 ◽  
pp. 595-598
Author(s):  
Francisco N.C. Freitas ◽  
Manoel Ribeiro da Silva ◽  
Sergio S.M. Tavares ◽  
Hamilton F.G. Abreu
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Cold Rolling ◽  
Crystallographic Texture ◽  
Electrical Steel ◽  
Electron Backscatter Diffraction ◽  
Magnetization Direction ◽  
Electrical Steels ◽  
Cold Rolling And Annealing ◽  
Work Samples

Non-oriented grain type electrical steels are used mainly in electrical rotating machines such as motors and compressors, in which the magnetization direction rotates 360 ° every cycle while remaining in the plane of the plate. The performance of these devices is affected by crystallographic texture of electrical steels due to strong anisotropy of magnetic properties. The electrical steel is supplied in the form of plates which are processed by cold rolling and subsequent annealing. Both, cold rolling and annealing directly influence the formation of crystallographic texture components. During annealing, recrystallization occurs, and this phenomenon gives rise to changes in texture that influences the quality of the final product and its application. Several works have been published in the study of the evolution of crystallographic texture and grain size in this type of electrical steel. In this work, samples have been taken in industrial conditions at various temperatures during the annealing in a coil box. Electrical steel samples cold rolled with reductions of 50% and 70% in thickness were removed during the process of annealing, and the evolution of texture with increasing temperature was studied. Aspects related to recrystallization, grain size and the evolution of texture and magnetic properties were discussed. Texture and recrystallization were studied by X-ray diffraction and electron backscatter diffraction (EBSD). The magnetic properties were measured in a vibrating sample magnetometer.

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