Mechanical alloying and theoretical studies of MnAl(C) magnets

Nguyen, Van Tang; Calvayrac, F.; Bajorek, A.; Randrianantoandro, N.

doi:10.1016/j.jmmm.2018.05.001

Cited by 19 publications

(9 citation statements)

References 49 publications

(71 reference statements)

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“…The remaining phase compositions show the trade-off between τ-MnAl in Figure 1a and the decrease in ε-MnAl in Figure 1b. The trend is consistent with the ε → τ phase transformation upon annealing at around 450-550 • C [10,11,[23][24][25]. In the case of the MnAl-C3, the intensity of the major τ-MnAl peak is significantly reduced, but the minor peak at 53.3 • is increased.…”

Section: Mnal-c Powders After Annealingsupporting

confidence: 81%

“…For the highest C doping (MnAl-C3), the ε phase is at the lowest in Figure 1b and monotonically decreases with increasing annealing temperature. On the other hand, the τ phase reaches the maximum by annealing at 550 • C. Hence, the C doping not only shifts the ε → τ phase transformation to a higher temperature, but also inhibits the decomposition of τ phase [10,11,25].…”

Section: Mnal-c Powders After Annealingmentioning

confidence: 99%

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Effects of Carbon Doping and Annealing Temperature on Magnetic MnAl Powders and MnAl Polymeric Composites

et al. 2021

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Process parameters leading to magnetic polymer composites, an essential ingredient in the additive manufacturing of rare-earth-free magnets, are investigated. The induction melting of manganese (Mn) and aluminum (Al), and subsequent annealing at 450, 500, or 550 °C for 20 min, gave rise to ferromagnetic τ–MnAl phase, as well as other phases. The nonmagnetic Al4C3 and oxide phases were then removed by the magnetic separation. Magnetic powders from the magnetic separation were incorporated in polylactic acid (PLA) matrix via a solution route. The remanent magnetization as high as 4.3 emu/g in the powder form was reduced to 2.3–2.6 emu/g in the composites. The reduction in coercivity was minimal, and the largest value of 814 Oe was obtained when the powder annealed at 450 °C was loaded in the composite. The phase composition and hence magnetic properties were even more sensitive to the carbon (C) doping. Interestingly, the addition of 3% C led to coercivity as high as 1445 Oe in MnAl–C powders without further annealing. The enhanced coercivity was attributed to the domain wall pinning by the AlMn3C phase, and magnetizations are likely increased by this phase.

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Section: Mnal-c Powders After Annealingsupporting

confidence: 81%

Section: Mnal-c Powders After Annealingmentioning

confidence: 99%

Effects of Carbon Doping and Annealing Temperature on Magnetic MnAl Powders and MnAl Polymeric Composites

et al. 2021

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“…Meanwhile, according to the ab-initio calculation, when carbon atoms occupied interstitial sites of L1 0 -type structure,¸-phase stabilized. 29) Although both¸and ¾-phase was stabilized by carbon addition, it is suggested by thermal analysis for quenched ¾-phase that ¾-phase becomes stabilized against¸-phase by carbon addition. 30,31) Consequently, carbon addition on the reactive sintering can be explained as below.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Ferromagnetic τ-Mn–Al–C by Reactive Sintering

et al. 2021

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Ferromagnetic MnAlC (¸-phase) can be synthesized by a single-route conventional reactive sintering method. The maximum magnetization and coercivity were 75.8 Am 2 /kg and 57 mT, respectively. The¸-phase fraction was evaluated to be 81 mass% for Mn 55 Al 45 C 2 annealed at 1273 K. The¸-phase of Mn 55 Al 45 C 2 can be synthesized at an annealing temperature from 873 to 1273 K, whereas that of Mn 55 Al 45 cannot be synthesized. It was indicated that the phase stability of the hcp-phase (¾-phase) was improved by adding carbon, resulting in an ¾ţ ransformation.

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“…at 375 °C). The (BH) max below 1 MGOe is typical for MnAl alloys [24]. We have also calculated the (BH) max for ribbons exhibiting the highest M s , (i.e.…”

Section: Spark Plasma Sintering Of Mnal Powders To Make a Bulk Magnetmentioning

confidence: 98%

“…Different research groups reported varying magnetic properties. For example, H c ranges from less than 1 kOe to ~10.7 kOe [18][19][20][21][22][23][24][25][26]. The highest H c is reported for the ultra-thin films (~11 nm) epitaxially grown on GaAs substrate [26].…”

Section: Introductionmentioning

confidence: 99%

Investigations on low energy product of MnAl magnets through recoil curves

Tong¹,

Sharma²,

Makino³

2020

J. Phys. D: Appl. Phys.

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Ferromagnetic τ-MnAl is being investigated as a potential candidate for the development of rare-earth-free permanent magnets. Maximum energy product (BH)max is reported to be much lower than the expectations based on saturation magnetization (Ms), and magnetocrystalline anisotropy (K). We have reinvestigated the MnAl alloy to shed light on low (BH)max. We made ribbons of Mn54Al46 alloy and annealed them at different temperatures. As-quenched ribbons (ASQ) are mainly made from non-magnetic ε-MnAl and a weakly magnetic phase. Low-temperature annealing (Ta = 300 °C) causes rapid improvement in magnetic properties without significant changes in ε-phase, suggesting that the weakly magnetic phase is metastable. Magnetic properties remain similar until transformation of ε- to τ-phase starts in Ta range of 350 °C–450 °C. Ribbons annealed at Ta = 450 °C are made up of a homogeneous Mn-rich τ-phase. Ribbons exhibiting high Ms (maximum ~125 emu g−1) show low coercivity (Hc, maximum ~2.04 kOe), or vice versa. Highest (BH)max obtained in the present study is 1.42 MGOe. It is considerably low due to a poor squareness (Mr/Ms, Mr is the remanence) of hysteresis curve in second quadrant. Based on detailed structural and magnetic characterization, we show that the metastability of ferromagnetic MnAl phase along with the presence of Mn–Mn antiferromagnetic coupling is responsible for low (BH)max. Recoil measurements suggest that the ribbons are made from grains with a large distribution of K. This is due to the formation of τ-phase in a wide composition range (Mn ~ 50 to 60 at.%) with the highest thermal stability ~Mn55Al45. The wide distribution of K results in a low hysteresis squareness. Improvements in (BH)max require minimization of Mn–Mn antiferromagnetic interactions, narrowing of anisotropy distribution, and breakdown in intergranular exchange. The improvements in (BH)max seems difficult unless the addition of a third element is considered.

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Mechanical alloying and theoretical studies of MnAl(C) magnets

Cited by 19 publications

References 49 publications

Effects of Carbon Doping and Annealing Temperature on Magnetic MnAl Powders and MnAl Polymeric Composites

Effects of Carbon Doping and Annealing Temperature on Magnetic MnAl Powders and MnAl Polymeric Composites

Synthesis of Ferromagnetic τ-Mn–Al–C by Reactive Sintering

Investigations on low energy product of MnAl magnets through recoil curves

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