Invar effect of Fe-based bulk metallic glasses

Hu, Qiang; Wang, J. M.; Yan, Yuqiang; Guo, Sheng; Chen, S. S.; Lu, Deping; Zou, Jiao; Zeng, Xie

doi:10.1016/j.intermet.2017.10.012

Cited by 19 publications

(9 citation statements)

References 36 publications

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“…where L is the sample length, T is the temperature, L 0 is the sample length at room temperature. The equiatomic FeNiCo and non- for equiatomic FeNiCo, a peak-type Invar effect is observed which means that the low TEC temperature range is quite narrow compared to the reference material [29]. Fig.…”

Section: Thermal Expansion Behaviormentioning

confidence: 90%

“…Among these anomalous properties, large spontaneous volume magnetostriction is believed to be the essential character related to the Invar alloys. As a result, another term, i.e., Invar-type alloys, is used to denote the alloys with large spontaneous volume magnetostriction and abnormally lower TEC (not necessarily lower than 2 × 10 −6 K −1 ) compared to conventional alloys [25][26][27][28][29][30]. For instance, Fe-Cu alloys prepared by mechanical alloying are not Invar alloys but show an Invar effect, e.g.…”

Section: Introductionmentioning

confidence: 99%

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Invar effects in FeNiCo medium entropy alloys: From an Invar treasure map to alloy design

et al. 2019

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To facilitate the understanding of Invar effects and design of FeNiCo-base Invar alloys characterized by low thermal expansion coefficient (TEC), we investigated the magnetic and thermal expansion behavior of an equiatomic prototype medium entropy alloy FeNiCo and a non-equiatomic (super Invar) Fe 63 Ni 32 Co 5 (at. %) reference alloy by means of experiments and ab initio calculations. Both alloys consist of a single face-centered cubic phase with fully recrystallized microstructure in the homogenized state. Large spontaneous volume magnetostriction is observed in both alloys below their respective Curie temperatures. The Invar effect in the non-equiatomic Fe 63 Ni 32 Co 5 alloy is of step-type with nearly zero TEC over a wide temperature range (from room temperature to 120°C) below its Curie temperature. The equiatomic FeNiCo alloy shows a peak-type Invar effect in a very narrow temperature range (from ∼675°C to ∼730°C) with relatively low TECs. The equiatomic FeNiCo alloy shows both higher saturation magnetization and Curie temperature than the non-equiatomic Fe 63 Ni 32 Co 5 alloy. The relationships among magnetic behavior, spontaneous volume magnetostriction and Invar effects for a wider array of metallic alloys are discussed mainly based on Masumoto's rule combined with Wohlfarth's itinerant electron theory. An Invar alloy search map is constructed based on the present results and available literature data to visualize the relationships among saturation magnetization, Curie temperature and thermal expansion coefficient for a wide range of Invar alloys. Based on this treasure map a design route for further developments of new Invar alloys by tuning their magnetic properties is discussed.

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Section: Thermal Expansion Behaviormentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Invar effects in FeNiCo medium entropy alloys: From an Invar treasure map to alloy design

et al. 2019

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“…For instance, the average of the local activation energy for the fourth stage of crystallization of the (Fe 41 Co 7 Cr 15 Mo 14 Y 2 C 15 B 6 ) 100−x Cu x (where x = 0.5 at.%) is the highest activation energy value compared to the fourth stages of the other two alloys. It is notable that the higher energy barrier, the slower reaction [ 65 , 66 , 67 , 68 , 69 ]. On the other hand, the activation energies for the crystallization process of the investigated BMGs are more than the other Fe-based BMGs [ 70 , 71 , 72 , 73 ].…”

Section: Resultsmentioning

confidence: 99%

Isokinetic Analysis of Fe41Co7Cr15Mo14Y2C15B6 Bulk Metallic Glass: Effect of Minor Copper Addition

et al. 2020

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In the present study, (Fe41Co7Cr15Mo14Y2C15B6)100−xCux (x = 0, 0.25 and 0.5 at.%) amorphous alloys were prepared by copper-mold casting. To clarify the effect of the minor addition of copper on the mechanism of nucleation and growth during the crystallization process, an isokinetic analysis was performed. The activation energies (E) of the various crystallization stages were calculated by using theoretical models including Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Augis–Bennett and Gao–Wang methods. In addition, Augis–Bennett, Gao–Wang and Matusita methods were used to investigate the nucleation and growth mechanisms and to determine other kinetic parameters including Avrami exponent (n), the rate constant (Kp) and dimensionality of growth (m). The obtained results revealed that the activation energy—as well as thermal stability—was changed with minor addition of copper. In addition, the obtained Avrami exponent values were confirmed by Johnson–Mehl–Avrami–Kolmogorov (JMAK) method. The research findings demonstrated that the value of Avrami exponent is changed with minor addition of copper, so that the Avrami exponents of all crystallization stages, except the second peak for copper-free amorphous alloy, were equal to integer values ranging from two to four, indicating that the growth mechanisms were controlled by interface. Moreover, the kinetic parameters of n and b for all peaks were increased by an increase in crystallization temperature, which can be attributed to the increase in the nucleation rate.

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“…This correlation of thermal expansion with the alloy’s magnetic state became known as the Invar effect. Although this effect is rare in crystalline materials, it is universally observed in all ferromagnetic Fe-based BMGs 7 – 9 . It is worth pointing out that Fe–Ni increases its CTE by a factor of 10 at its dilatometric transition temperature, whereas the CTE of ferromagnetic Fe-based BMGs is only reduced by a factor of 2–5 in the ferromagnetic state compared to the CTE in the paramagnetic state (which is also close to that of pure Fe).…”

Section: Introductionmentioning

confidence: 99%

Atomic structure evolution related to the Invar effect in Fe-based bulk metallic glasses

et al. 2022

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The Invar effect is universally observed in Fe-based bulk metallic glasses. However, there is limited understanding on how this effect manifests at the atomic scale. Here, we use in-situ synchrotron-based high-energy X-ray diffraction to study the structural transformations of (Fe71.2B24Y4.8)96Nb4 and (Fe73.2B22Y4.8)95Mo5 bulk metallic glasses around the Curie temperature to understand the Invar effect they exhibit. The first two diffraction peaks shift in accordance with the macroscopically measured thermal expansion, which reveals the Invar effect. Additionally, the nearest-neighbor Fe–Fe pair distance correlates well with the macroscopic thermal expansion. In-situ X-ray diffraction is thus able to elucidate the Invar effect in Fe-based metallic glasses at the atomic scale. Here, we find that the Invar effect is not just a macroscopic effect but has a clear atomistic equivalent in the average Fe–Fe pair distance and also shows itself in higher-order atomic shells composed of multiple atom species.

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Invar effect of Fe-based bulk metallic glasses

Cited by 19 publications

References 36 publications

Invar effects in FeNiCo medium entropy alloys: From an Invar treasure map to alloy design

Invar effects in FeNiCo medium entropy alloys: From an Invar treasure map to alloy design

Isokinetic Analysis of Fe41Co7Cr15Mo14Y2C15B6 Bulk Metallic Glass: Effect of Minor Copper Addition

Atomic structure evolution related to the Invar effect in Fe-based bulk metallic glasses

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