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Artificially produced rare-earth free cosmic magnet.

Makino A, Sharma P, Sato K, Takeuchi A, Zhang Y, Takenaka K - Sci Rep (2015)

Bottom Line: Electron diffraction detects four-fold 110 superlattice reflections and a high chemical order parameter (S  0.8) for the developed L10-FeNi phase.The magnetic field of more than 3.5 kOe is required for the switching of magnetization.Experimental results along with computer simulation suggest that the ordered phase is formed due to three factors related to the amorphous state: high diffusion rates of the constituent elements at lower temperatures when crystallizing, a large driving force for precipitation of the L10 phase, and the possible presence of L10 clusters.

View Article: PubMed Central - PubMed

Affiliation: Tohoku University, Sendai 980-8577, Japan.

ABSTRACT
Chemically ordered hard magnetic L10-FeNi phase of higher grade than cosmic meteorites is produced artificially. Present alloy design shortens the formation time from hundreds of millions of years for natural meteorites to less than 300 hours. Electron diffraction detects four-fold 110 superlattice reflections and a high chemical order parameter (S  0.8) for the developed L10-FeNi phase. The magnetic field of more than 3.5 kOe is required for the switching of magnetization. Experimental results along with computer simulation suggest that the ordered phase is formed due to three factors related to the amorphous state: high diffusion rates of the constituent elements at lower temperatures when crystallizing, a large driving force for precipitation of the L10 phase, and the possible presence of L10 clusters. Present results can resolve mineral exhaustion issues in the development of next-generation hard magnetic materials because the alloys are free from rare-earth elements, and the technique is well suited for mass production.

No MeSH data available.


Related in: MedlinePlus

Calculated results and theoretical consideration for forming L10 from the amorphous and crystalline phases.(a) FeNi phase diagram calculated with SSOL5 database. (b) Gibbs free energy curves at T = 673 K for liquid, bcc, and fcc phases calculated with the SSOL5 database as functions of the Ni fraction together with G = –35 kJmol–1 for the L10 phase estimated from previous studies. (c) Characteristics of the phases of interest, including the driving force to precipitate L10 at T = 673 K. (d) Changes in Gibbs free energy (G) of fcc phase as a function of Si content in a hypothetical Fe50Ni50-Fe50−x/2Ni50−x/2Six system where G = –35 kJmol−1 was considered for L10 Fe50Ni50 phase. Based on lever rule (marked by red arrow), the volume fraction of the L10 phase is evaluated to be ~13% in Fe42Ni41.3Si8B4P4Cu0.7 alloy under an assumption that L10 FeNi phase precipitates from the fcc Fe45Ni45Si10, which is an equilibrium phase at T = 673 K in the alloy.
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f4: Calculated results and theoretical consideration for forming L10 from the amorphous and crystalline phases.(a) FeNi phase diagram calculated with SSOL5 database. (b) Gibbs free energy curves at T = 673 K for liquid, bcc, and fcc phases calculated with the SSOL5 database as functions of the Ni fraction together with G = –35 kJmol–1 for the L10 phase estimated from previous studies. (c) Characteristics of the phases of interest, including the driving force to precipitate L10 at T = 673 K. (d) Changes in Gibbs free energy (G) of fcc phase as a function of Si content in a hypothetical Fe50Ni50-Fe50−x/2Ni50−x/2Six system where G = –35 kJmol−1 was considered for L10 Fe50Ni50 phase. Based on lever rule (marked by red arrow), the volume fraction of the L10 phase is evaluated to be ~13% in Fe42Ni41.3Si8B4P4Cu0.7 alloy under an assumption that L10 FeNi phase precipitates from the fcc Fe45Ni45Si10, which is an equilibrium phase at T = 673 K in the alloy.

Mentions: Figure 4 schematically diagrams the above thermodynamic results. The binary phase diagram of Fe–Ni Fig. 4a calculated using the widely accepted SSOL5 database demonstrates that Fe50Ni50 (at.%) is thermodynamically stable as a single fcc phase at T = 673 K (as drawn with both arrows). Analysis of GFig. 4b also indicates a single fcc phase, and Fe50Ni50 is the composition at the edge of the phase separation between bcc (Symbol E in Fig. 4b) and fcc (a composition close to Symbol C marked with open circle in Fig. 4b).


Artificially produced rare-earth free cosmic magnet.

Makino A, Sharma P, Sato K, Takeuchi A, Zhang Y, Takenaka K - Sci Rep (2015)

Calculated results and theoretical consideration for forming L10 from the amorphous and crystalline phases.(a) FeNi phase diagram calculated with SSOL5 database. (b) Gibbs free energy curves at T = 673 K for liquid, bcc, and fcc phases calculated with the SSOL5 database as functions of the Ni fraction together with G = –35 kJmol–1 for the L10 phase estimated from previous studies. (c) Characteristics of the phases of interest, including the driving force to precipitate L10 at T = 673 K. (d) Changes in Gibbs free energy (G) of fcc phase as a function of Si content in a hypothetical Fe50Ni50-Fe50−x/2Ni50−x/2Six system where G = –35 kJmol−1 was considered for L10 Fe50Ni50 phase. Based on lever rule (marked by red arrow), the volume fraction of the L10 phase is evaluated to be ~13% in Fe42Ni41.3Si8B4P4Cu0.7 alloy under an assumption that L10 FeNi phase precipitates from the fcc Fe45Ni45Si10, which is an equilibrium phase at T = 673 K in the alloy.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4644987&req=5

f4: Calculated results and theoretical consideration for forming L10 from the amorphous and crystalline phases.(a) FeNi phase diagram calculated with SSOL5 database. (b) Gibbs free energy curves at T = 673 K for liquid, bcc, and fcc phases calculated with the SSOL5 database as functions of the Ni fraction together with G = –35 kJmol–1 for the L10 phase estimated from previous studies. (c) Characteristics of the phases of interest, including the driving force to precipitate L10 at T = 673 K. (d) Changes in Gibbs free energy (G) of fcc phase as a function of Si content in a hypothetical Fe50Ni50-Fe50−x/2Ni50−x/2Six system where G = –35 kJmol−1 was considered for L10 Fe50Ni50 phase. Based on lever rule (marked by red arrow), the volume fraction of the L10 phase is evaluated to be ~13% in Fe42Ni41.3Si8B4P4Cu0.7 alloy under an assumption that L10 FeNi phase precipitates from the fcc Fe45Ni45Si10, which is an equilibrium phase at T = 673 K in the alloy.
Mentions: Figure 4 schematically diagrams the above thermodynamic results. The binary phase diagram of Fe–Ni Fig. 4a calculated using the widely accepted SSOL5 database demonstrates that Fe50Ni50 (at.%) is thermodynamically stable as a single fcc phase at T = 673 K (as drawn with both arrows). Analysis of GFig. 4b also indicates a single fcc phase, and Fe50Ni50 is the composition at the edge of the phase separation between bcc (Symbol E in Fig. 4b) and fcc (a composition close to Symbol C marked with open circle in Fig. 4b).

Bottom Line: Electron diffraction detects four-fold 110 superlattice reflections and a high chemical order parameter (S  0.8) for the developed L10-FeNi phase.The magnetic field of more than 3.5 kOe is required for the switching of magnetization.Experimental results along with computer simulation suggest that the ordered phase is formed due to three factors related to the amorphous state: high diffusion rates of the constituent elements at lower temperatures when crystallizing, a large driving force for precipitation of the L10 phase, and the possible presence of L10 clusters.

View Article: PubMed Central - PubMed

Affiliation: Tohoku University, Sendai 980-8577, Japan.

ABSTRACT
Chemically ordered hard magnetic L10-FeNi phase of higher grade than cosmic meteorites is produced artificially. Present alloy design shortens the formation time from hundreds of millions of years for natural meteorites to less than 300 hours. Electron diffraction detects four-fold 110 superlattice reflections and a high chemical order parameter (S  0.8) for the developed L10-FeNi phase. The magnetic field of more than 3.5 kOe is required for the switching of magnetization. Experimental results along with computer simulation suggest that the ordered phase is formed due to three factors related to the amorphous state: high diffusion rates of the constituent elements at lower temperatures when crystallizing, a large driving force for precipitation of the L10 phase, and the possible presence of L10 clusters. Present results can resolve mineral exhaustion issues in the development of next-generation hard magnetic materials because the alloys are free from rare-earth elements, and the technique is well suited for mass production.

No MeSH data available.


Related in: MedlinePlus