Accepted Manuscript

Formation, magnetic properties and bending deformation of Fe-based amorphousalloy without metalloids

Chunxiao Xie, Yuanzheng Yang, Shouyan Zhong, Sheng Li, Shichun Deng

PII: S0925-8388(16)33305-9

DOI: 10.1016/j.jallcom.2016.10.182

Reference: JALCOM 39349

To appear in: Journal of Alloys and Compounds

Received Date: 24 August 2016

Revised Date: 17 October 2016

Accepted Date: 18 October 2016

Please cite this article as: C. Xie, Y. Yang, S. Zhong, S. Li, S. Deng, Formation, magnetic properties andbending deformation of Fe-based amorphous alloy without metalloids, Journal of Alloys and Compounds(2016), doi: 10.1016/j.jallcom.2016.10.182.

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Formation, magnetic properties and bending deformation of Fe-based amorphous alloy without metalloids

Chunxiao Xie1*,Yuanzheng Yang2,Shouyan Zhong1,Sheng Li1, Shichun Deng1

1School of Mechanical Engineering, Dongguan University of Technology,

Dongguan, 523808, China

2Faculty of Materials and Energy, Guangdong University of Technology,

Guangzhou, 510006, China

Keywords: Fe-based amorphous alloy; Metalloid elements; Magnetic properties; Bending deformation.

Abstract. In this work, we synthesized a new Fe-based amorphous alloy without metalloids, X-ray diffractometer(XRD), differential scanning calorimeter (DSC), vibrating sample magnetometer(VSM) and scanning electron microscope(SEM) were adopted to study the formation, thermals stability, magnetic properties and bending ductility of (Fe0.52Co0.48-xNix)73Cr17Zr10 (x=0.18,0.30) amorphous alloy ribbons. The amorphous alloys exhibit certain magnetic properties, through proper annealing conditions, The saturation magnetization(Ms) and coercivities (Hc) values of the annealed ribbons can reach up to 112.8A·m2

·kg−1 and 6.6Oe, respectively. In additional, the as-spun and annealed alloy ribbons show good bending ductility, they will become promising functional/structural materials in the future.

1. Introduction

In the last half century, a great number of amorphous alloys have been synthesized, among these alloys, Fe-based metallic glasses have been particularly investigated due to not only their unique combination of excellent magnetic properties, high fracture strength, high hardness and good corrosion resistance, but also the low cost resulting from plentiful nature resources of iron on the earth[1,2].

In order to obtain good glass forming ability(GFA) and then to prepare Fe-based amorphous alloys with larger size, usually one or more types of metalloid elements(B, C, Si, P and so on) have been added in Fe-based amorphous alloys. Now Fe-based amorphous alloys have been developed in various alloy systems including (Fe,Co)-(Al,Ga,Sn)-(P,B,C,Si)[3], (Fe,Co,Ni)-(Zr,Nb,Ta)-(Mo,W)-B[4], Fe-Ni-P-B[5], Fe-C-Si-(B,P)[6], (Fe,Co,Ni)-Si-B[7], Fe-(Sc,Y,Dy,Ho,Er)-B[8], Fe-Nb-B[9], Fe-Pt-B-P[10], Fe-Mo-(PCBSi)[11], Fe-(CrMoMn)-(CB)[12], (Fe,Co)-P-C[13] and Fe-Cu-B-Si-Nb[14]. But all these Fe-based amorphous alloys show great brittleness, such as almost no plastic deformation in compression test, and their elastic deformation ability is also limited, which makes them difficult to handle and limits their industrial and commercial applications. Study on the brittleness of Fe-based * Corresponding author. Tel./ fax: +86 0769 22861122.

E-mail address: xiechx@dgut.edu.cn(C.X. Xie).

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amorphous alloy ribbons and bulks showed that their brittleness is closely related with types, contentand distribution of metalloid elements[15-17]. At present, Fe-based amorphous alloy without metalloids is rarely reported[18,19].

In the present study, based on the reported experimental results, through big-cluster-structure crystalline phase and deep eutectic point rule, with the aim of synthesizing a new Fe-based amorphous alloys without metalloids, and simultaneously exhibiting good mechanical properties or magnetic properties, the compositions of FeCoNiCrZr amorphous alloys were designed and the samples were synthesized successfully.

2. Experimental procedures

Alloy ingots with nominal compositions (Fe0.52Co0.48-xNix)73Cr17Zr10 at% x=0.06 0.18 0.30;

0.48 were prepared by means of Ti-gettered arc melting in Ar atmosphere. High purity

elements(Fe 99.9%, Co 99.9%, Ni 99.9%, Cr 99.9% and Zr 99.9%) were used to obtain master

ingots of 8g. The alloy ingot was re-melted four times to ensure homogeneity. It was necessary to

polish the surface of the Fe-based alloy ingot for ensuring high pure master alloys before they

were crushed into small pieces. For the production of ribbons, the nozzle size of the crucible was 1

mm in diameter. Rapidly solidified ribbons with 25~35µm in thickness and 2~3mm in width were

obtained by melt spinning technique at a wheel speed of 50m/s in an argon atmosphere.

The structure of as-spun and annealed ribbons was identified by Rigaku D/MAX-2200 X-ray

diffractometer(XRD) with CuKα radiation, the scanning range in the analysis was from 20° to 80°.

The thermal properties of as-spun ribbons were examined by SDT-2960 differential scanning

calorimetry (DSC) at a heating rate of 20K/s. All of the ribbons for magnetic property

measurements were annealed for improving magnetic properties. The hysteresis M-H loops Ms

and Hc were measured with WK- vibrating sample magnetometer(VSM) under a field of

-5000~5000 Oe. Ten samples of 50mm long of each alloy were prepared for bending tests.

Ribbons that showed the ability to be bent 180°and then bent to straight shape without fracture

were classified as ductile. The bent fractured ribbon morphologies were observed in S-3400N

scanning electron microscope(SEM) operated at 15 kV.

3. Results and discussion

The amorphous nature of samples in the as-spun has been confirmed by X-ray diffraction technique. The XRD patterns of the as-quenched (Fe0.52Co0.48-xNix)73Cr17Zr10 ribbons are shown in Fig.1. Only broad peaks without appreciable crystalline peaks can be observed, which are characteristic of an amorphous structure. With further increasing the value of x to 0.48 or decreasing x to 0, the as-spun structure changed to crystalline phases and amorphous phase.

DSC curves of the as-spun (Fe0.52Co0.48-xNix)73Cr17Zr10 amorphous alloys are shown in Fig.2. Two exothermic peaks are seen on these DSC curves, indicating that the crystallization takes place through two stages. The onset temperature of the first crystallization peak(Tx1) decreases gradually from 872 K to 821 K with increasing Ni content from x=0.18 to x=0.30. However, no distinct glass transition phenomenon is observed for all amorphous alloys. On the other hand, Tx2 increases from 977 K to 1002 K with decreasing Ni content from x=0.30 to x=0.18. As a result, there is a tendency for the temperature interval between the two exothermic peaks to increase

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with increasing Ni/Co ratios.

Fig.1 XRD patterns of (Fe0.52Co0.48-xNix)73Cr17Zr10 Fig.2 DSC curves of (Fe0.52Co0.48-xNix)73Cr17Zr10

(x=0.18,0.30) alloy ribbons (x=0.18,0.30) alloy ribbons

To determining precipitation phases corresponding to these exothermic peaks, structures of the alloys subjected to annealing under different conditions were examined by XRD. The XRD patterns of the as-spun (Fe0.52Co0.30Ni0.18)73Cr17Zr10 and (Fe0.52Co0.18Ni0.30)73Cr17Zr10 amorphous alloy, as well as the samples annealed for 20min at 760 K and 723K(which is lower than Tx1), 831 K and 800K(which is higher than Tx1), 1012 K and 987K(which is higher than Tx2) are shown in Fig.3, respectively. When annealing at 760 K and 723K, because of structural relaxation, only broad peaks without appreciable crystalline peaks can be observed. It is obviously seen that the diffraction pattern consists of two peaks after annealing at 831 K and 800K, which can be indexed as α-Fe(Co) phase. While, the diffraction peaks after annealing at 1012 K and 987K are identified as α-Fe(Co), Cr2Ni3 , Fe3Ni2 , Cr2Zr and unidentified phase.

Thus, the two peaks correspond to the primary precipitation of α-Fe(Co) and the decomposition of the remaining amorphous phase to α-Fe(Co) ,Cr2Ni3 , Fe3Ni2 , Cr2Zr and unidentified phase, respectively.

Fig.3. XRD patterns of (Fe0.52Co0.48-xNix)73Cr17Zr10 amorphous alloys annealed at different temperatures

(a)x=0.18 (b)x=0.30 The magnetic properties of as-spun and annealed samples were further investigated.

Fig.4(a) shows relation between Ms and annealing temperatures of (Fe0.52Co0.48-xNix)73Cr17Zr10 (x=0.18,0.30) amorphous alloys. We can see the Ms values of as-spun (Fe0.52Co0.48-xNix)73Cr17Zr10 (x=0.18,0.30) amorphous alloys are low, which yield 34.0A·m2

·kg−1 and 25.1A·m2·kg−1, respectively. When annealing at 760 K

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and 723K, because of structural relaxation, the Ms values of samples increased to 60.6A·m2

·kg−1 and 53.3A·m2·kg−1, respectively. Because of the precipitation of lots of

ferromagnetic α-Fe(Co) phase, it is obviously seen that the Ms increased greatly after annealing at 831K and 800K, which yield 112.8A·m2

·kg−1 and 101.4A·m2·kg−1,

respectively. While, Because of the precipitation of nonferromagnetic phases, the Ms values of (Fe0.52Co0.48-xNix)73Cr17Zr10 (x=0.18,0.30) amorphous alloys decreased dramasticly after annealing at 1012 K and 987K, respectively.

Fig.4(b) shows relation between Hc and annealing temperatures of these amorphous

alloys. We can see the Hc values of as-spun (Fe0.52Co0.48-xNix)73Cr17Zr10 (x=0.18,0.30) amorphous alloys are high, which yield 23.0Oe and 25.2Oe, respectively. When annealing at 760 K and 723K, the Hc values of samples decreased to 11.9Oe and 14.1Oe, respectively. Because of the formation of nanocrystalline/amorphous composite dual phase structure after annealing at 831K and 800K, it is obviously seen that the Hc values decreased to 6.6Oe and 7.5Oe, respectively. While, Because of the grain coarsening weakening the exchange-coupling interaction between grains , increasing the magnetocrystalline anisotropy, the Hc values of samples increased greatly after annealing at 1012 K and 987K, which yield 121.0Oe and 108.0Oe, respectively.

Fig.4. Relation between Ms (a)/Hc(b) and annealing temperatures of (Fe0.52Co0.48-xNix)73Cr17Zr10 (x=0.18,0.30)

amorphous alloys

For bulk or ribbon of amorphous alloys, it has been reported that brittle fracture happens almost immediately at the beginning of bending deformation, in conjunction with the mechanism and criterion for the brittle fracture[20,21]. Besides, there are a lot of data on extremely brittle nature for nanocrystalline Fe-based alloys obtained upon annealing amorphous alloy ribbons, and the mechanism for the brittle nature has also been investigated[22,23]. In the present study, we have found that the (Fe0.52Co0.48-xNix)73Cr17Zr10(x=0.18,0.30) alloy ribbons exhibit better bending ductility in as-spun and annealed states.

As an example, Fig.5 shows the bent fracture surface SEM morphologies of (Fe0.52Co0.30Ni0.18)73Cr17Zr10 amorphous alloy. In Fig.5(a), above the white solid line is the side section of the sample, it is obviously seen that a number of shear bands show bend or step-like movement and the orientation of the shear band is parallel to the direction of the stress bending load. The shear bands resulted by bending were formed rapidly at the beginning of deformation. It has been reported [24] that the deformation

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of the deep and large shear bands should give rise to compositional disordering during high stress deformation or through an increase in the average atomic volume. In Fig.5(a), under the white solid line is the fracture surface of the sample, Fig.5(b),(c) and (d) are the local enlarged views of (B), (C) and (D) in Fig.5(a), respectively. As can be seen from Fig.5(b)(c) and (d), a larger number of dimple patterns are densely distributed on the fracture surface and most of the width of dimple patterns are relatively uniform, the average width is about 1µm. As a result, the larger number of shear bands and dimple patterns indicate plastic deformation has been produced in the process of bending deformation.

Fig.5. Bent fracture surface SEM morphologies of (Fe0.52Co0.30Ni0.18)73Cr17Zr10 amorphous alloy

(a); (b) (c) and (d) are the local enlarged views of (B), (C) and (D) in (a), respectively

4. Conclusions

Through composition design, a new Fe-based amorphous alloy without metalloids has been synthesized successfully. We examined the formation, thermals stability, magnetic properties and bending ductility of (Fe0.52Co0.48-xNix)73Cr17Zr10 (x=0.18,0.30) amorphous alloy ribbons. The Ms values of as-spun ribbons are low, but through proper annealing conditions, The Ms and Hc values of the annealed ribbons can reach up to 112.8A·m2

·kg−1 and 6.6Oe, respectively. The as-spun and annealed alloy ribbons show good bending ductility. Therefore, improving GFA and magnetic properties of this alloy system through optimization of alloy composition design, it will become a promising functional/structural material.

Acknowledgement

This work is financially supported by National Natural Science of Foundation of

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Highlights

1.A new Fe-based amorphous alloy without metalloids was synthesized.

2.The nominal compositions:(Fe0.52Co0.48-xNix)73Cr17Zr10（at%）(x=0.18,0.30).

3.The Ms and Hc of annealed alloy reach up to 112.8A·m2·kg−1and 6.6Oe,respectively.

4.The as-spun and annealed alloy ribbons show good bending ductility.