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Within this modern era like right now, many ways to get information are available for you. From media social including newspaper, magazines, science book, encyclopedia, reference book, novel and comic. View 3 excerpts, cites background. The powders were prepared using a … Expand. View 1 excerpt. Microstructure, distortion characteristics and mechanical behaviour of NiB modified 90W-6Ni-4Co heavy alloys. Abstract In this work, the effect of NiB on densification, phase, microstructure, distortion and mechanical properties of conventionally sintered ternary 90W-6Ni-4Co heavy alloy has been investigated … Expand.
In this work, the effects of boron nitride additions on the microstructures and tensile behaviours of microalloyed powder metallurgy PM steels were investigated. The microstructure of the … Expand. View 2 excerpts, cites results. On the application of Electro-sinter-forging to the sintering of high-karatage gold powders. Gold Bulletin. Precious metals are widely used for a variety of applications, among which are luxury goods, biomedical devices, and electronic components.
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Allow this favorite library to be seen by others Keep this favorite library private. Save Cancel. It is very clear to recognise the Nd-rich phase at the grain boundaries, surrounding almost all the particles of the hard phase Nd 2 Fe 14 B. In general, the maximum value of this sintered density is usually considered as a criterion of the quality of the sintering process, unless otherwise is specified. It seems that the best magnetic properties probably often achieved by employing Powder metallurgy routes rather than casting processes.
Although in some cases a combination between them is used in the manufacturing of permanent magnets. Careful control of particle size and particle orientation, using a magnetic field to align the starting particles, are among two of the greatest advantages of the powder metallurgy process.
Chemical composition, impurities, and metallic and non-metallic inclusions probably controlled by using powder techniques. Additionally, extremely pure powders and freedom from inclusions are easy to attain by powder metallurgy processing. Composition of the permanent magnets may be limited in precision by the purity with which powder can be produced.
In fact, all these factors mentioned above play a vital role in controlling and enhancing the magnetic properties of permanent magnets and soft magnets as well. The products of powder metallurgy almost semi-finished produced to specifications with different shapes and sizes, so from this point of view the powder metallurgy technique is very advantageous as the machining stage can be dispensed with, thus decreasing costs and saving materials. These materials are hard to magnetise and demagnetise.
Magnetic hardness is obviously related with the microstructure, heat treatment and chemical composition of the starting material. Magnetically hard substances are made into permanent magnets which provide magnetic field in working air, or vacuum gapes. The distinguishing characteristics of hard magnets are large hysteresis loops, high remanence and corercivity with different Curie temperatures.
Permanent magnets are fundamentally energy storage systems when they are magnetised. Development of hard magnetic materials is in the direction of obtaining improved magnetic properties, reducing the cost of production and the volume of material required. Hard magnets are used to perform a wide variety of magnetic functions, such as in electrical machines, motors, computers, direct drive motors, electrodynamic braking, clamping and holding devices for ferrous materials, loudspeakers, magnetic sealing, head-phones, focusing and steering of charged particles, medical equipment, etc.
This was mixed with linseed oil, the paste moulded into shape and baked hard. The resulting blocks were then magnetised and formed strong magnets for that time, reputedly [13]. The beauty of this story shows that the beginning of the development of the first permanent magnet by powder metallurgy primitive technique. In the 's, the idea of this process of surrounding hard phase particles with non-magnetic material has been strongly re-introduced for producing permanents magnets [14,15].
Some ferrites tend to be dissociated during heating at elevated temperature, so that the conventional route of melting and casting is impractical for ferrites, and ferrites are normally fabricated by Powder metallurgy [16]. If a magnetic filed is applied during the cooling or tempering while the temperature is just below the Curie point, a crystallographic growth along the direction of the applied filed which is nearest to the easy axis is encouraged. This process called magnetic annealing, the first attempt of this process was carried out at Sheffield UK , and in it was found that heat treatment in a suitable magnetic field could enhance the magnetic properties of Alnicos permanent magnets [17].
This process was also used in the production of Sm-Co permanent magnets to solidify the ingots from the liquid state in a magnetic field produces oriented polycrystalline materials [18]. The production of magnets, by employing powder metallurgy technology probably give improved products because of the simplicity of aligning most of the powder particles along the easy direction at room temperature, and hence producing anisotropic compacts.
The degree of alignment is influenced by particle shape, particle size distribution, magnitude of aligning field, and pressing pressure. The remanennce and the energy product are thereby sharply enhanced [19]. Magnetic alignment of Nd-Fe-B hydride powder using a flexible bag is shown in Fig. In , synthesis of magnetite particle-chain microwires by applying magnetic field during the fabrication process has been firstly reported by Fashen et al.
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