Magnetic properties of alnico 5 and alnico 8 phases at the sequential stages of heat treatment in a field

Sergeyev, V.A.; Bulygina, T.

doi:10.1109/tmag.1970.1066745

Cited by 20 publications

(8 citation statements)

References 4 publications

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“…Alnico is a functional nanostructured alloy due to the spinodal decomposition of the solid solution into a magnetic Fe-Co-rich (α 1 ) phase and an Al-Ni-rich (α 2 ) phase during cooling [3], [4]. This class of permanent magnets was developed in the 1930s and the complex processing, heat treatment, and compositions were optimized empirically over the following decades [5]- [11]. Alnico magnets exhibit coercivity from shape anisotropy after thermal annealing in a magnetic field, resulting in the spinodal nanoscale structure elongated along the applied field direction [3], [4].…”

Section: Introductionmentioning

confidence: 99%

Net Shape Processing of Alnico Magnets by Additive Manufacturing

et al. 2017

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Alternatives to rare earth permanent magnets, such as alnico, will reduce supply instability, increase sustainability, and could decrease the cost of permanent magnets, especially for high temperature applications, such as traction drive motors. Alnico magnets with moderate coercivity, high remanence, and relatively high energy product are conventionally processed by directional solidification and (significant) final machining, contributing to increased costs and additional material waste. Additive manufacturing (AM) is developing as a cost effective method to build net-shape three-dimensional parts with minimal final machining and properties comparable to wrought parts. This work describes initial studies of net-shape fabrication of alnico magnets by AM using a laser engineered net shaping (LENS) system. High pressure gas atomized (HPGA) pre-alloyed powders of two different modified alnico "8" compositions, with high purity and sphericity, were built into cylinders using the LENS process, followed by heat treatment. The magnetic properties showed improvement over their cast and sintered counterparts. The resulting alnico permanent magnets were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and hysteresisgraph measurements. These results display the potential for net-shape processing of alnico permanent magnets for use in next generation traction drive motors and other applications requiring high temperatures and/or complex engineered part geometries.Alternatives to rare earth permanent magnets, such as alnico, will reduce supply instability, increase sustainability, and could decrease the cost of permanent magnets, especially for high temperature applications, such as traction drive motors. Alnico magnets with moderate coercivity, high remanence, and relatively high energy product are conventionally processed by directional solidification and (significant) final machining, contributing to increased costs and additional material waste. Additive manufacturing (AM) is developing as a cost effective method to build net-shape three-dimensional parts with minimal final machining and properties comparable to wrought parts. This work describes initial studies of net-shape fabrication of alnico magnets by AM using a laser engineered net shaping (LENS) system. High pressure gas atomized (HPGA) pre-alloyed powders of two different modified alnico "8" compositions, with high purity and sphericity, were built into cylinders using the LENS process, followed by heat treatment. The magnetic properties showed improvement over their cast and sintered counterparts. The resulting alnico permanent magnets were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and hysteresisgraph measurements. These results display the potential for net-shape processing of alnico permanent magnets for use in next generation traction drive motors and other applications requiring hi...

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Section: Introductionmentioning

confidence: 99%

Net Shape Processing of Alnico Magnets by Additive Manufacturing

et al. 2017

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“…As a result, magnetic properties of alnico strongly depend on the details of its unique microstructure: a periodically arrayed elongated Fe-Co rich (α 1 ) hard magnetic phase embedded in a continuous non-magnetic Ni-Al-rich (α 2 ) matrix, formed via SD. Achieving the optimum properties in alnico requires a well controlled and lengthy heat-treatment process, including solutionization of the alloy above 1200 • C, isothermal MA near its Curie temperature and subsequent lower temperature annealing (draw cycles) [1,[8][9][10][11][12]. The application of MA marks the most important cornerstone in alnico magnets' development history.…”

Section: Introductionmentioning

confidence: 99%

On spinodal decomposition in alnico - A transmission electron microscopy and atom probe tomography study

et al. 2018

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Alnico is a prime example of a finely tuned nanostructure whose magnetic properties are intimately connected to magnetic annealing (MA) during spinodal transformation and subsequent lower temperature annealing (draw) cycles. Using a combination of transmission electron microscopy and atom probe tomography, we show how these critical processing steps affect the local composition and nanostructure evolution with impact on magnetic properties. The nearly 2fold increase of intrinsic coercivity (H ci ) during the draw cycle is not adequately explained by chemical refinement of the spinodal phases. Instead, increased Fe-Co phase (α 1 ) isolation, development of Cu-rich spheres/rods/blades and additional α 1 rod precipitation that occurs during the MA and draw, likely play a key role in H ci enhancement. Chemical ordering of the Al-Ni-phase (α 2 ) and formation of Ni-rich (α 3 ) may also contribute. Unraveling of the subtle effect of these nano-scaled features is crucial to understanding on how to improve shape anisotropy in alnico magnets.

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“…Introduction: Alnico alloys commonly contain some 6-12%A1, 14-25%Ni, 0-35%Co, 0-8%Ti and 0-6%Cu in 40-70%Fe and are distinguished by a number appended to their generic description. Below 845OC [ 3 ] , Alnico alloys are prone to spinodal decomposition resulting in the separation of two crystallographically isomorphous but compositionally dissimilar magnetic phases [4,5,6]; b.c.c. Fe-Co-rich and b.c.c Ni-Al-rich (see for example [2]).…”

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confidence: 99%