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Journal of Alloys and Compounds 693 (2017) 25e31

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Journal of Alloys and Compounds

journal homepage: http: / /www.elsevier .com/locate/ ja lcom

New soft magnetic Fe25Co25Ni25(P, C, B)25 high entropy bulk metallicglasses with large supercooled liquid region

Yanhui Li, Wei Zhang*, Tianlong QiKey Laboratory of Solidification Control and Digital Preparation Technology (Liaoning Province), School of Materials Science and Engineering, DalianUniversity of Technology, Dalian, 116024, China

a r t i c l e i n f o

Article history:Received 8 August 2016Received in revised form12 September 2016Accepted 13 September 2016Available online 14 September 2016

Keywords:High-entropy alloysBulk metallic glassesSupercooled liquid regionMagnetic propertiesMechanical properties

* Corresponding author.E-mail address: wzhang@dlut.edu.cn (W. Zhang).

http://dx.doi.org/10.1016/j.jallcom.2016.09.1440925-8388/© 2016 Elsevier B.V. All rights reserved.

a b s t r a c t

New Fe25Co25Ni25(P, C, B)25 high entropy bulk metallic glasses (HE-BMGs) with large supercooled liquidregion (DTx) and excellent soft magnetic and mechanical properties were developed. Fully HE-BMG rodswere successfully prepared by copper mold casting in the composition region of 7.5e12.5 at% P, 7.5e10 at% C, and 5e10 at% B, respectively. The HE-BMGs possess low glass transition temperature (Tg) of ~672 Kand large DTx of ~56 K, which are comparable to those of Zr-based BMGs, whereas exhibit much higheryield strength of ~3210 MPa with distinct plasticity. The alloys also show low coercivity of ~1.2 A/m andhigh saturation magnetization of ~0.86 T. The mechanism of good stability of the supercooled liquid andthe correlation between strength and Tg for the HE-BMGs were discussed.

© 2016 Elsevier B.V. All rights reserved.

1. Introduction

High entropy alloys (HEAs), typically defined as the alloyscomposing of at least five principal elements in equal or near equalatomic percent (at.%) ranging 5 to 35 at.%, are becoming the newresearch frontier in materials filed [1,2]. The high mixing entropy ofHEAs stabilizes the solid-solution phases in face-centered-cubic(FCC), body-centered-cubic (BCC), and hexagonal close-packed(HCP) structure instead of complex intermetallics [3e5]. Recently,quaternary CoCrFeNi [6] and CoFeNiAl/Si [7] alloys with FCCstructure have been prepared, which extends the HEAs to quater-nary alloy systems. In contrast, bulk metallic glasses (BMGs),known as another type of advancedmaterials, usually contain morethan two kinds of elements but only one, sometimes two principalconstituents [8]. Due to their considerably different characteristicsin structure and composition rules, the HEAs and BMGs have beenstudied independently until the HEAs with amorphous structure,namely high entropy bulk metallic glasses (HE-BMGs) were suc-cessfully synthesized by Ma et al. in 2002 [9]. The developed HE-BMGs provide a new strategy to design and synthesis BMGs.More importantly, the HE-BMGs possess excellent mechanical and

physical properties inherited from the advantages of both HEAs andBMGs, and show great potential for practical applications [10,11].

Till now, serials of HE-BMG systems have been developed[12e19]. The Ti20Zr20Hf20Be20Cu7.5Ni12.5 HE-BMG [17] has a criticaldiameter (dc) up to 30 mm, and the Ti20Zr20Hf20Be20Cu20 HE-BMG[18] exhibits wide supercooled liquid region (DTx ¼ Tx � Tg, Tx:crystallization temperature, Tg: glass transition temperature) of78 K, which indicates that the HE-BMGs can possess comparableglass forming ability (GFA) and thermal stability of supercooledliquid to the traditional Zr-based BMGs [20]. By taking the advan-tages of viscous flow workability in the supercooled liquid regiontogether with the unique mechanical and physical properties, theHE-BMGs are hopeful to be utilized for making micro- and nano-devices in Micro- and Nano-electromechanical Systems (MEMS/NEMS) [21]. The work referring to the functional properties of HE-BMGs were rarely reported although the magnetic properties ofmetallic glasses have been studied comprehensively [11]. In addi-tion, the developed HE-BMGs with large dc and DTx always containtoxic element Be [15e18] or noble element Pt/Pb [13], which wouldbring difficulty to the production or consumption.

Most of the pre-developed HE-BMGs contain metallic or rareearth elements, while only a few metallic-metalloid type of HE-BMGs have been discovered. Very recently, we reported pseudo-quaternary Fe25Co25Ni25(B, Si)25 HE-BMGs with good soft mag-netic and mechanical properties [19]. These soft magnetic HE-

Fig. 1. DSC (a) and DTA (b) curves of melt-spun Fe25Co25Ni25(PxC0.8�xB0.2)25(x ¼ 0.2e0.6) metallic glasses.

Y. Li et al. / Journal of Alloys and Compounds 693 (2017) 25e3126

BMGs exhibit a high strength of over 3200 MPa, which is superiorto other HE-BMGs. While the high Tg (>767 K) and small DTx(<40 K) of the HE-BMGs make it difficult to be used for thermo-plastic forming. To overcome the disadvantage of the pre-developed HE-BMGs, we here developed new Fe25Co25Ni25(P, C,B)25 HE-BMGs possessing low Tg, large DTx, combined with excel-lent mechanical and soft magnetic properties, which show greatpotential for making MEMS/NEMS devices by thermoplasticprocessing.

2. Experimental procedure

Alloy ingots of Fe25Co25Ni25(P, C, B)25 in at.% were prepared byinduction melting of Fe (99.9 mass%), Co (99.9 mass%), Ni (99.95mass%), C (99.999 mass%), B (99.5 mass%), and Fe3P precursor (99.9mass%) under Ti-gettered argon atmosphere. The ingots were re-melted 4 times to ensure chemical homogeneity, and the masslosses were less than 0.2%. The alloys were produced by injectioncopper mold casting method for bulk cylindrical rods with di-ameters of 1e2 mm and a length of about 20 mm, and by a single-roller melt spinner for the ribbons with a cross section of about0.02 mm � 1.2 mm. To examine the crystallization products, themelt-spun ribbons were sealed into a quartz tube, evacuated to2 � 10�3 Pa, isothermally annealed for 600 s at different temper-atures, and then quenched into water. The structure of the sampleswas examined by X-ray diffraction (XRD) (Cu Ka). A cross-section ofalloy rod with a diameter of 1 mm was etched, and subsequentlyobserved by optical microscopy. The thermal stability of the sam-ples was examined by differential scanning calorimetry (DSC) at aheating rate of 0.67 K/s. The liquidus temperature (Tl) of the alloyswas measured with a differential thermal analyzer (DTA) at aheating rate of 0.33 K/s. The saturation magnetization (Is) of ribbonsamples was measured under an applied field of 800 kA/m with avibrating sample magnetometer (VSM). The coercive force (Hc) wasmeasured with a B-H loop tracer using ribbons about 60 mm inlength. Themelt-spun ribbons for magnetic property measurementwere annealed for 300 s at temperatures of 100 K below theirrespective Tg to release the internal stress. The mechanical prop-erties under compressive load were measured using an Instronmechanical testing machine. The gauge dimension of specimens formechanical test was 1 mm in diameter and 2mm in height, and thestrain rate was fixed as 5.0 � 10�4 s�1. The fracture surface wasobserved with a scanning electron microscope (SEM).

3. Results

A fully glassy phase was confirmed by XRD results for the melt-spun Fe25Co25Ni25(P, C, B)25 alloy ribbons. Fig. 1 shows the DSC andDTA curves of the melt-spun Fe25Co25Ni25(PxC0.8�xB0.2)25(x ¼ 0.2e0.6) metallic glasses, and the Tg, Tx, and Tl are marked byarrows, respectively. It is seen that the alloys all exhibit a clearendothermic event associated with glass transition followed by aseries of exothermic peaks due to crystallization (see Fig. 1(a)). TheTg of the metallic glasses are in the region of 671e695 K, and Tx are714e740 K. The DTx increases from 37 to 56 K as x increases from0.2 to 0.5, and then decreases to 45 K with x ¼ 0.6. It should benoted that the Tg of Fe25Co25Ni25(PxC0.8�xB0.2)25 metallic glasses iscomparable to those of the Zr-based BMGs [20], but quite lowerthan the most Fe-based BMGs [22] and previously reportedFe25Co25Ni25(B, Si)25 HE-BMGs [19]. The large DTx up to 56 K in-dicates good thermal stability of the supercooled liquid for thepresent metallic glasses. As shown in Fig. 1(b), the Tl of the alloysdecreases remarkable from 1263 to 1228 K with increasing x from0.2 to 0.3, and then increases to 1262 K with further increasing x to0.6. Table 1 lists theDTx, reduced glass transition temperature Trg (¼

Tg/Tl) [23], g (¼ Tx/(Tl þ Tg)) [24], and S (¼ DTx/(Tl � Tg)) [25] valuesof the Fe25Co25Ni25(PxC0.8�xB0.2)25 metallic glasses. It is seen thatthe DTx, g, and S values rise simultaneously as x increase from 0.2 to0.5, and then decrease with further increasing x to 0.6, which in-dicates that the alloys with x around 0.5 possess higher GFA.

We further investigated the thermal properties of Fe25Co25-Ni25(P, C, B)25 metallic glasses in an extended composition rangewith P, C, and B contents of 5e15 at.%, respectively. The thermalparameters, namely Tg, Tx, DTx, Tl, Trg, g, and S values of Fe25Co25-Ni25(P, C, B)25 alloys are summarized in Table 1. It is seen that the Tgand Tx show an upward trend with B increasing from 5 to 15 at.%,respectively. The DTx over 45 K is obtained in a wide compositionrange of 7.5e15 at.% P, 10e17.5 at.% C, and 5e10 at.% B. In addition,the g and S values respectively show a good correlation with DTx.

The GFA of Fe25Co25Ni25(P, C, B)25 alloys was evaluated by cop-per mold casting method. Fig. 2(a) shows the XRD patterns of theas-cast Fe25Co25Ni25(P0.4C0.4B0.2)25, Fe25Co25Ni25(P0.5C0.3B0.2)25, andFe25Co25Ni25(P0.3C0.3B0.4)25 alloy rods with a diameter of 1 mm. Thepatterns all consist of only a series of broad diffraction maximawithout any detectable sharp Bragg peaks, indicating that thesamples have a fully glassy structure. Fig. 2(b) shows the cross-

Table 1The thermal properties, critical diameters (dc), magnetic and mechanical properties of Fe25Co25Ni25(P, C, B)25 metallic glasses.

Composition (at.%) Tg (K) Tx (K) DTx (K) Tl (K) Trg g S dc (mm) Is (T) Hc (A/m) sy (MPa) εp (%)

Fe25Co25Ni25(P0.2C0.6B0.2)25 683 720 37 1263 0.541 0.370 0.064 <1 0.85 6.4 e e

Fe25Co25Ni25(P0.3C0.5B0.2)25 671 714 43 1228 0.546 0.376 0.077 <1 0.83 3.3 e e

Fe25Co25Ni25(P0.4C0.4B0.2)25 672 720 48 1234 0.545 0.378 0.085 1 0.84 2.5 2817 1.1Fe25Co25Ni25(P0.5C0.3B0.2)25 674 730 56 1239 0.544 0.382 0.099 1 0.86 1.2 2850 1.2Fe25Co25Ni25(P0.6C0.2B0.2)25 695 740 45 1262 0.551 0.378 0.079 <1 0.71 2.0 e e

Fe25Co25Ni25(P0.2C0.4B0.4)25 699 739 40 1315 0.532 0.367 0.065 <1 0.76 4.3 e e

Fe25Co25Ni25(P0.3C0.3B0.4)25 702 749 47 1293 0.543 0.375 0.080 1 0.80 3.4 3210 0.3Fe25Co25Ni25(P0.4C0.2B0.4)25 708 753 45 1278 0.554 0.379 0.079 <1 0.78 3.5 e e

Fe25Co25Ni25(P0.2C0.2B0.6)25 723 759 36 1355 0.534 0.365 0.057 <1 0.84 4.1

Y. Li et al. / Journal of Alloys and Compounds 693 (2017) 25e31 27

sectional optical morphology of the etched Fe25Co25-Ni25(P0.5C0.3B0.2)25 alloy rod with a diameter of 1 mm. No obviouscrystalline grains can be seen in the cross-section of the sample butthe homogeneous glassy phase (see Fig. 2(b)). This is consistentwith the XRD results. The XRD results combined with optical

Fig. 2. X-ray diffraction patterns of as-cast Fe25Co25Ni25(P, C, B)25 alloy rods with adiameter of 1 mm (a), and cross-sectional optical morphology of as-cast Fe25Co25-Ni25(P0.5C0.3B0.2)25 alloy rod with a diameter of 1 mm (b).

morphologies demonstrate that the metallic glasses in bulk form(dc ¼ 1 mm) can be obtained for Fe25Co25Ni25(P0.4C0.4B0.2)25,Fe25Co25Ni25(P0.5C0.3B0.2)25, and Fe25Co25Ni25(P0.3C0.3B0.4)25 alloys,respectively. Fig. 3 shows the composition dependence of the DTxand dc of the present metallic glasses. It is seen that the alloyspossessing DTx over 45 K, as circled in the dashed line, have a dc of1 mm, indicating the good correlation between the GFA and DTx. Inaddition, the GFA of the alloys shows a better correlation with S

Fig. 3. Composition dependences of supercooled liquid region DTx (a) and criticalglassy sample diameter dc (b) for Fe25Co25Ni25(P, C, B)25 metallic glasses.

Fig. 5. Compressive stress-strain curves of as-cast Fe25Co25Ni25(P, C, B)25 BMG rodswith a diameter of 1 mm (a), and SEM micrographs of lateral (b) and fracture surfacemorphology (c) of cracked Fe25Co25Ni25(P0.5C0.3B0.2)25 BMG sample.

Y. Li et al. / Journal of Alloys and Compounds 693 (2017) 25e3128

parameters than Trg and/or g (see Table 1).Fig. 4 shows the room temperature hysteresis loops of

Fe25Co25Ni25(P0.4C0.4B0.2)25 and Fe25Co25Ni25(P0.5C0.3B0.2)25metallic glasses. Both the alloys exhibit a typical soft magnetichysteresis characteristic. Although the Is not so high due to the lowFe content, the Hc is low enough. It is seen in Table 1 that thepresent metallic glasses possess good soft magnetic properties, i.e.,high Is of 0.71e0.86 T, and low Hc of 1.2e6.4 A/m.

Fig. 5 (a) shows the nominal compressive stress-strain curves ofthe as-cast Fe25Co25Ni25(P, C, B)25 BMGs with a diameter of 1 mm.Under the compressive loading, all alloys exhibit an initial elasticdeformation with an elastic limit around 2%, and then begin toyield, followed by an obvious plastic deformation. Series of distinctserrates can be found in the stress-strain curves before finalrupture, indicating the generation of shear bands. The compositiondependence of yield stress (sy), and plastic strain (εp) are summa-rized in Table 1. The present BMGs have a rather high sy of2817e3210 MPa, and εp of 0.3e1.2%, respectively. Fig. 5(b, c) showthe SEM images of the lateral and fracture surface morphology ofthe cracked Fe25Co25Ni25(P0.5C0.3B0.2)25 alloy sample. Series ofmultiple shear bands can be observed on the whole lateral surface,which are consistent with the generation of the serrated plasticflow during plastic deformation. In addition, the fracture surfaceexhibits a well-developed vein pattern (see Fig. 5 (c)), which istypical of the tough BMGs.

Table 2 summarizes the thermal properties (Tg, DTx), GFA (dc),and mechanical properties (sy, εp) of the present Fe25Co25Ni25(P, C,B)25 and previously reported typical HE-BMGs [9,12e19]. It is seenthat the present alloys possess superior strength and comparablylow Tg and large DTx to those HE-BMGs based on Zr-based BMGs,although the GFA is inferior to the Be-containing alloys. In addition,the present alloys exhibit lower Tg and larger DTx than those of theFe25Co25Ni25(B, Si)25 HE-BMGs.

4. Discussion

The HEAs can form solid solutions or an amorphous phase.Zhang [26] and Guo et al. [27,28] have suggested that the phaseselection in HEAs between solid solutions and the amorphousphase is controlled by a topology natured atomic size poly-dispersity, d, and a chemistry natured mixing enthalpy, DHmix,

which are defined as: d ¼ 100ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiPn

i¼1cið1� ri=rÞ2q

, and

Fig. 4. Hysteresis loops of melt-spun Fe25Co25Ni25(P, C, B)25 metallic glasses.

DHmix ¼ Pni¼1;isjcicjUij, where r ¼ Pn

i¼1ciri; ci and ri are the atomicpercentage and atomic radius of the ith element, n is the number ofalloying elements, Uij ¼ 4DHAB

mix, and DHABmix is the mixing enthalpy

of binary liquid equiatomic alloys. The amorphous phase can formwhen d is large enough and DHmix is noticeably negative. The

mixing entropy DSmix (¼ �RPN

i¼1cilnci, R is the gas constant) isbelieved to determine the phase formation as well [26e28]. Fig. 6shows the DHmix - d (a) and DSmix - d plots delineating the phaseselection in HEAs. The formation regions of HE-BMGs and solid-solutions are respectively delineated by dashed lines according toGuo's results [27], i.e., HE-BMGs can formwhen d, DHmix and DSmixsimultaneously satisfy d � 9, -49 � DHmix � �5.5 kJ/mol, and7 � DSmix � 16 J/(K$mol), whereas solid solutions can form when0� d � 8.5, �22� DHmix �7 kJ/mol, and 11� DSmix �19.5 J/(K$mol).We calculated the d, DHmix and DSmix of the present Fe25Co25Ni25(P,C, B)25 and pre-developed typical HE-BMGs (see Table 2). Theatomic radii and DHAB

mix values were taken from Refs. [10] and [29],respectively. It is seen in Fig. 6 that the HE-BMGs are all located inthe predicted region for HE-BMGs formation, which indicates thatthe phase selection rules determined by d, DHmix and DSmix areuniversal for HE-BMGs in different alloy systems.

The phase formation regions in Fig. 6 are definitely distinguishedby d, which suggests that the d is a critical parameter for amorphousor solid solution phase formation. The necessity of a large d to formthe amorphous phase shall originate from the requirement on thesufficient atomic-level stress to destabilize the solid solution phase[30,31]. In addition, a large d and negative DHmix would improve thelocal packing efficiency and restrain the long-range diffusion ofatoms. The crystalline phase formation will be suppressed duringthe cooling process, which leads to a high GFA [32,33]. Similarly, the

Table 2Glass transition temperature (Tg), supercooled liquid region (DTx), critical diameter for glass formation (dc), yield stress (sy), plastic strain (εp), average atom-size difference (d),mixing enthalpy (DHmix), and mixing entropy (DSmix) of typical high entropy alloys.

Composition (at.%) Tg (K) DTx (K) dc (mm) sy (MPa) εp (%) d DHmix DSmix

Ti20Zr20Hf20Cu20Ni20 [9] 658 53 1.5 1920 0.3 10.32 �27.36 13.38Zn20Ca20Sr20Yb20(Li0.55Mg0.45)20 [12] 323 25 3 383 25 15.71 �12.15 14.53Pd20Pt20Cu20Ni20P20 [13] 580 65 10 e e 9.29 �23.68 13.38Sr20Ca20Yb20Mg20(Zn0.5Cu0.5)20 [14] 351 40 5 423 0 16.37 �10.6 14.54Ti20Zr20Cu20Ni20Be20 [15]$ 683 46 3 2315 0 12.53 �30.24 13.38Ti16.7Zr16.7Hf16.7Cu16.7Ni16.7Be16.7 [16] 681 70 15 1943 0.6 12.77 �31.67 14.90Ti20Zr20Hf20Be20Cu7.5Ni12.5 [17] 632 50 30 2067 3.0 13.15 �33.39 14.48Ti20Zr20Hf20Be20Cu20 [18] 630 78 12 1889 2.3 12.89 �25.44 13.38Fe25Co25Ni25(B0.7Si0.3)25 [19] 767 40 1.5 3624 1.7 13.79 �22.91 12.84Fe25Co25Ni25(B0.6Si0.4)25 [19] 771 37 1 3239 3.1 12.86 �23.99 12.93Fe25Co25Ni25(P0.4C0.4B0.2)25 (In this work) 672 48 1 2817 1.1 14.26 �28.87 12.47Fe25Co25Ni25(P0.5C0.3B0.2)25 (In this work) 674 56 1 2850 1.2 13.23 �28.27 12.42Fe25Co25Ni25(P0.3C0.3B0.4)25 (In this work) 702 47 1 3210 0.3 14.77 �26.57 11.87

Y. Li et al. / Journal of Alloys and Compounds 693 (2017) 25e31 29

nucleation and growth of crystalline phases will be inhibited in thesupercooled liquid state, which results in a wide supercooled liquidregion. In addition, high mixing entropy could enhance the confu-sion level, complicate competing crystalline phases and frustratethe process of crystallization, which also leads to the increase of GFAand supercooled liquid stability [34].

Fig. 6. DHmix-d (a) and DSmix-d (b) plots delineating the phase selection in HEAs.

To further understand themechanisms of the enhanced GFA andthermal stability of supercooled liquid, we examined the crystalli-zation behaviors of Fe25Co25Ni25(P, C, B)25 HE-BMGs. Fig. 7(a) showsthe XRD patterns of Fe25Co25Ni25(P0.5C0.3B0.2)25 metallic glasssubjected to annealing for 600 s at different temperatures. Forcomparison, the results of Fe75(P0.5C0.3B0.2)25 metallic glass(DTx ¼ 29 K, dc < 1 mm) are also shown in Fig. 7(b). For

Fig. 7. XRD patterns of Fe25Co25Ni25(P0.5C0.3B0.2)25 (a), and Fe75(P0.5C0.3B0.2)25 (b)metallic glasses subjected to annealing for 600 s at different temperatures. The XRDpatterns of melt-spun alloys are also shown for comparison.

Y. Li et al. / Journal of Alloys and Compounds 693 (2017) 25e3130

Fe25Co25Ni25(P0.5C0.3B0.2)25 metallic glass, an (Fe, Co, Ni)23(C, B)6phase with Fe23C6-type structure primarily precipitates in theamorphous matrix after annealing at 683 K (9 K above Tg) for 600 s.When the annealing temperature goes up to 703 K, an (Fe, Co, Ni)3Pphase forms accompanying with the (Fe, Co, Ni)23(C, B)6 phase.When the annealing temperature is up to 803 K, the (Fe, Co, Ni)3Pphase transforms to an (Fe, Co, Ni)3(B, P) phase, and a new (Fe, Co,Ni)3C phase forms. In addition, the (Fe, Co, Ni)23(C, B)6 phase stillexists at the elevated temperature (see Fig. 7(a)). Note that there isno simple fcc and/or bcc phase formation during the crystallization.For Fe75(P0.5C0.3B0.2)25 metallic glass, however, an Fe3(B, P) phasefirstly forms after annealing at 723 K (11 K below Tg) for 600 s.When the annealing temperature rises to 733 K, themixed Fe3C andFe3(B, P) phases form, and they keep stable even at the annealingtemperature of over 803 K (see Fig. 7(b)). It has been reported thatthe primary precipitation of the Fe23C6-type phase with a complexfcc structure in amorphous matrix requires to destroy the strongbonding nature followed by long-range atomic rearrangements ofconstituent elements [35,36]. Therefore, the difficulty of the (Fe, Co,Ni)23(C, B)6 phase precipitation leads to the high stability of thesupercooled liquid of Fe25Co25Ni25(P, C, B)25 HE-BMGs. In addition,the successful suppression of the primary competing phase isbeneficial for increase of GFA as well. Consequently, the presentFe25Co25Ni25(P, C, B)25 HE-BMGs simultaneously possess large DTxand high GFA.

It is well known that the strength of BMGs show a good corre-lation with their Tg [37e39]. Liu et al. [39] proposed a universalscaling law to describe the inherent relationship of the yieldstrength with the molar-volume-normalized Tg of metallic glasses:ty ¼ 3RðTg � RTÞ=V , where ty (zsy/2) is yield shear stress, R is gasconstant, RT represents the room-temperature, and V is molarvolume, which can be calculated according to the rule of mixtures[40,41]. Fig. 8 shows the ty vs (Tg-RT)/V of the present Fe25Co25-Ni25(P, C, B)25 and some other typical HE-BMGs [9,12e19], in whichty is calculated from sy/2. It is seen that the ty of HE-BMGs allexhibit a distinct dependence on (Tg-RT)/V in a linear manner. Thelinear fitting slope of ty vs (Tg-RT)/V is (2.8 ± 0.1)R, which is quiteclose to 3R as deduced by Liu. This indicates that the correlationbetween strength and Tg is also valid for the HE-BMGs. It seemsinconsistent that the Tg (672e702 K) of the present Fe25Co25Ni25(P,C, B)25 HE-BMGs are much lower than those (~771 K) of the

Fig. 8. The relationship between yield stress ty and (Tg-RT)/V of HE-BMGs.

Fe25Co25Ni25(B, Si)25 HE-BMGs, whereas the sy (2817e3210 MPa) iscomparable to the pre-reported alloys (~3239 MPa). It should benoted that the atomic radii of P (0.1060 nm) and C (0.0773 nm) inFe25Co25Ni25(P, C, B)25 HE-BMGs are smaller than that of Si(0.1153 nm) in Fe25Co25Ni25(B, Si)25 alloys, which results in thepresent HE-BMGs possess smaller V. Consequently, the equationty ¼ 3RðTg � RTÞ=V can be well fit by higher strength, lower Tg,together with much lower V of the present HE-BMGs. This can alsoexplain the phenomenon of the present HE-BMGs exhibit muchhigher strength than that of Zr-based BMGs but possess a compa-rable Tg.

5. Conclusion

New soft magnetic Fe25Co25Ni25(P, C, B)25 HE-BMGs with largesupercooled liquid region were developed. The Fe25Co25-Ni25(P0.4C0.4B0.2)25, Fe25Co25Ni25(P0.5C0.3B0.2)25, and Fe25Co25-Ni25(P0.3C0.3B0.4)25 HE-BMGs possess a dc of 1 mm, low Tg of672e702 K, and large DTx of 47e56 K. The HE-BMGs also exhibitlow coercivity of 1.2e3.4 A/m, high saturation magnetization of0.80e0.86 T, high yield strength of 2817e3210 MPa, and distinctplastic strain of 0.3e1.2%. The large DTx, low Tg, combined withexcellent soft magnetic and mechanical properties make the newlydeveloped HE-BMGs have great potential for making MEMS/NEMSdevices by thermoplastic processing.

Acknowledgement

This work was financially supported by Natural Science Foun-dation of China (Grant Nos. 51171034, 51271043, and 51571047) andthe Research Fund for the Doctoral Program of Higher Education(Grant No. 20130041110006).

References

[1] J.W. Yeh, S.K. Chen, S.J. Lin, J.Y. Gan, T.S. Chin, T.T. Shun, et al., Adv. Eng. Mater6 (2004) 299e303.

[2] B. Cantor, I.T.H. Chang, P. Knight, A.J.B. Vincent, Mater. Sci. Eng. A 375e377(2004) 213e218.

[3] Y. Zhang, T.T. Zuo, Z. Tang, M.C. Gao, K.A. Dahmen, P.K. Liaw, et al., Prog. Mater.Sci. 61 (2014) 1e93.

[4] A. Takeuchi, K. Amiya, T. Wada, K. Yubuta, W. Zhang, JOM 66 (2014)1984e1992.

[5] Y.J. Zhao, J.W. Qiao, S.G. Ma, M.C. Gao, H.J. Yang, M.W. Chen, et al., Mater. Des.96 (2016) 10e15.

[6] M.S. Lucas, G.B. Wilks, L. Mauger, J.A. Munoz, O.N. Senkov, E. Michel, et al.,Appl. Phys. Lett. 100 (2012), 251907e1e4.

[7] T.T. Zuo, R.B. Li, X.J. Ren, Y. Zhang, J. Magn. Magn. Mater. 371 (2014) 60e68.[8] W.L. Johnson, MRS Bull. 24 (1999) 42e56.[9] L.Q. Ma, L.M. Wang, T. Zhang, A. Inoue, Mater. Trans. 43 (2002) 277e280.

[10] Y. Zhang, X. Yang, P.K. Liaw, JOM 64 (2012) 830e838.[11] W.H. Wang, JOM 66 (2014) 2067e2077.[12] K. Zhao, X.X. Xia, H.Y. Bai, D.Q. Zhao, W.H. Wang, Appl. Phys. Lett. 98 (2011),

141913e1e3.[13] A. Takeuchi, N. Chen, T. Wada, Y. Yokoyama, H. Kato, A. Inoue, et al., In-

termetallics 19 (2011) 1546e1554.[14] K. Zhao, W. Jiao, J. Ma, X.Q. Gao, W.H. Wang, J. Mater. Res. 27 (2012)

2593e2600.[15] H.Y. Ding, K.F. Yao, J. Non Cryst. Solids 364 (2013) 9e12.[16] H.Y. Ding, Y. Shao, P. Gong, J.F. Li, K.F. Yao, Mater. Lett. 125 (2014) 151e153.[17] S.F. Zhao, Y. Shao, X. Liu, N. Chen, H.Y. Ding, K.F. Yao, Mater. Des. 87 (2015)

625e631.[18] S.F. Zhao, G.N. Yang, H.Y. Ding, K.F. Yao, Intermetallics 61 (2015) 47e50.[19] T.L. Qi, Y.H. Li, A. Takeuchi, G.Q. Xie, H.T. Miao, W. Zhang, Intermetallics 66

(2015) 8e12.[20] A. Inoue, Acta Mater. 48 (2000) 279e306.[21] G. Kumar, T. Golden, X. Hong, J. Schroers, Nature 457 (2009) 868e872.[22] C. Suryanarayana, A. Inoue, Int. Mater. Rev. 58 (2013) 131e166.[23] D. Turnbull, Contempt Phys. 10 (1969) 473e488.[24] Z.P. Lu, C.T. Liu, Acta Mater. 50 (2002) 3501e3512.[25] J. Schroers, JOM 57 (2005) 35e39.[26] Y. Zhang, Y.J. Zhou, J.P. Lin, G.L. Chen, P.K. Liaw, Adv. Eng. Mater. 10 (2008)

534e538.[27] S. Guo, C.T. Liu, Prog. Nat. Sci. Mater. Int. 21 (2011) 433e446.

Y. Li et al. / Journal of Alloys and Compounds 693 (2017) 25e31 31

[28] S. Guo, Mater. Sci. Technol. 31 (2015) 1223e1230.[29] A. Takeuchi, A. Inoue, Mater. Trans. 12 (2005) 2817e2829.[30] T. Egami, Y. Waseda, J. Non-Crystal. Solids 64 (1984) 113e134.[31] T. Egami, V. Levashov, R. Aga, J.R. Morris, Metall. Mater. Trans. A 39 (2008)

1786e1790.[32] A. Inoue, T. Zhang, T. Masumoto, J. Non-Cryst. Solids 156e158 (1993)

473e480.[33] X.H. Lin, W.L. Johnson, J. Appl. Phys. 78 (1995) 6514e6519.[34] A.L. Greer, Nature 366 (1993) 303e304.

[35] A. Inoue, B.L. Shen, Adv. Mater. 16 (2004) 2189e2192.[36] W. Zhang, F. Jia, X.G. Zhang, G.Q. Xie, H. Kimura, A. Inoue, J. Appl. Phys. 105

(2009), 053518e1e4.[37] W.L. Johnson, K. Samwer, Phys. Rev. Lett. 95 (2005), 195501e1e4.[38] W.H. Wang, J. Appl. Phys. 99 (2006), 093506e1e10.[39] Y.H. Liu, C.T. Liu, W.H. Wang, A. Inoue, T. Sakurai, M.W. Chen, Phys. Rev. Lett.

103 (2009), 065504e1e4.[40] D. Ma, A.D. Stoica, X.L. Wang, Appl. Phys. Lett. 91 (2007), 021905e1e3.[41] C.N. Singman, J. Chem. Educ. 61 (1984) 137e142.