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Thermoplastic deformation behavior of a Fe-based bulk metallic glass within the supercooled liquid region
j m a t e r r e s t e c h n o l . 2 0 1 9;8(2):1907–1914
Available online at www.sciencedirect.com
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Original Article
Thermoplastic deformation behavior of a Fe-based bulk metallic glass within the supercooled liquid region S.M. Song a , Y.C. Liao b , T.H. Li a , C.K. Lee a , P.H. Tsai a , J.S.C. Jang a,b,∗ , J.C. Huang c,d a
Institute of Materials Science and Engineering, National Central University, Chung-Li, Taoyuan 320, Taiwan Department of Mechanical Engineering, National Central University, Chung-Li, Taoyuan 320, Taiwan c Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan d Center for Advanced Study, City University of Hong Kong, Kowloon, Hong Kong Special Administrative Region b
a r t i c l e
i n f o
a b s t r a c t
Article history:
Fe41 Cr15 Co7 Mo14 C12 B9 Y2 (Fe-B9) bulk metallic glass (BMG) rods with high glass forming abil-
Received 27 July 2018
ity and large supercooled liquid (SCL) region were fabricated by arc melting and suction
Accepted 12 January 2019
casting. The amorphous state of these Fe-B9 BMG rods was ascertained by X-ray diffraction
Available online 19 February 2019
(XRD) and differential scanning calorimetry (DSC). The thermoplastic deformation behavior
Keywords:
(873 K, 883 K, 893 K, and 903 K in the SCL region) and strain rates (1 × 10−3 –5 × 10−2 s−1 ). The
of these BMG rods was studied by using the hot compression test at different temperatures Metallic glasses
results of the hot compression test reveal that the flow stress of Fe-B9 BMG reduces system-
Viscous flow
atically with increasing temperature and decreasing strain rate. Strain sensitivity exponent
Superplasticity
(m) values of the Fe-B9 BMG were calculated to be about 0.36–0.59 in the SCL region, indi-
Mechanical properties
cating that Fe-B9 BMG possesses superplasticity. Overall, the optimum working conditions of thermoplastic forming for Fe-B9 BMG can be achieved by compressively deforming the
Casting
sample with a constant strain rate of 2.5 × 10−3 s−1 at a temperature from 873 to 883 K. © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1.
Introduction
Fe-based bulk metallic glasses (BMGs), also called bulk amorphous steels, have attracted the attention of many scientists
∗
due to their unique properties, such as the ultrahigh hardness and fracture strength, superior wear resistance, excellent corrosion resistance, good magnetic properties, and higher thermal stability for engineering applications [1–10]. In addition, Fe-based BMG can be fabricated by using industrial raw materials (pig-iron and boron ferrous alloy), leading to a reduced production cost. Recently, some researchers have used Fe-based BMG to make surgical blades and apply a metallic glass thin film (MGTF) coating on the surgical blades.
Corresponding author. E-mail: [email protected] (J. Jang). https://doi.org/10.1016/j.jmrt.2019.01.007 2238-7854/© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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j m a t e r r e s t e c h n o l . 2 0 1 9;8(2):1907–1914
The edge-tip of both BMG-made and MGTF-coated blades is extremely flat. The surface roughness of the blade edge can decrease down to nanoscale due to the amorphous nature with no crystal defects. As a result, the cutting sharpness was enhanced significantly in comparison with commercial surgical blades [11–14]. In addition, the Fe-based BMG/MGTF blades exhibit much better cutting durability than the Zrbased BMG/MGTF blades [11] due to their ultrahigh hardness and superior wear resistance. Therefore, workers of amorphous alloys suggest that the Fe-based BMG can be a priority choice for surgical tools and other biomedical related parts. One of the most regarded features of metallic glasses is thermoplastic forming (TPF). This is typically carried out in the supercooled liquid region (SCL) between the glass transition temperature (Tg ) and the crystallization temperature (Tx ) where the metallic glass exhibits very low viscosity (∼107−8 Pa s) [15,16]. This TPF ability has been used for a wide range of applications, such as writing-erasing, blow molding, and surface embossing, particularly for complex-shaped micro-components of near-net-shape fabrication [16–25]. Febased BMGs do not easily form complex structures by traditional machine processing due to their ultrahigh hardness and relative brittleness compared with Zr-based BMGs. Therefore, the TPF process may be a good way to make the Fe-based BMG miniature parts for engineering and medical applications. Several Fe-based BMG TPF systems, such Co31 Fe31 Nb8 B30 [26], Fe78 B13 Si9 [27], Fe40 Co20 Ni15 P10 C10 B5 [28], have been developed. However, these alloys exhibit too low a glass-forming ability (GFA) to perform a TPF process for feasible engineering applications. In the literature, Fe41 Co7 Cr15 Mo14 C15 B6 Y2 BMG [29] was the first reported to have high GFA (critical size 16 mm), high fracture strength (3500 MPa), and ultrahigh hardness (1250 Hv). However, this Fe-based BMG exhibits a small SCL (Tx = 38 K), and is not easily used with TPF technology. Furthermore, by modifying the carbon/boron ratio from the previous Febased BMG, another Fe-based BMG, Fe41 Cr15 Co7 Mo14 C12 B9 Y2 (Fe-B9) with wide SCL (Tx = 81 K) has been explored [11]. This Fe-B9 BMG presents superior corrosion resistance in simulated body fluids, compared with 316 stainless steel. In this study, we investigate the thermoplastic deformation behavior of Fe41 Cr15 Co7 Mo14 C12 B9 Y2 BMG with industrial raw materials and characterize the process window of thermoplastic forming for further engineering applications.
1.1.
(XRD, Bruker D8A X-ray diffractometer) with monochromatic Cu-K␣ radiation. The XRD patterns were obtained from the central area of the BMG rods. Thermal analyses of the as-cast samples were carried out by differential scanning calorimeter (DSC, METTLER TOLEDO DSC 1) and high temperature differential scanning calorimeter (HTDSC, Netzsch STA449F3), respectively. The hardness of the specimens was measured by using a Vickers hardness tester (Mitutoyo, HM-220 Series 810) under a load of 2 kgf for 10 s.
Experimental procedure
The alloy ingots based on the compositions of Fe41 Cr15 Co7 Mo14 C12 B9 Y2 (Fe-B9) in atomic percentage were first prepared by arc melting of the appropriate mixture of ferrous alloys and pure elements, such as pig iron (94.2 wt.% Fe, 4.6 wt.% C, 1 wt.% Si, 0.2 wt.% P), ferro-boron (77.45 wt.% Fe, 21 wt.% B, 0.55 wt.% C), Cr3 C2 , Cr, Co, Mo, Fe, and Y (purity > 99%) under a Ti-gettered argon atmosphere. The ingots were re-melted at four times in the arc-melting furnace under purified argon atmosphere to ensure their homogeneity. Sample rods with a diameter of 2–4 mm were produced by suction-cast into the water-cooling Cu mold under a high purity Ar atmosphere. Amorphous state of the BMG rods was ascertained by X-ray diffraction analysis
Fig. 1 – (a) DSC scans of Fe-B9 BMG sample with different scanning rates, (b) Plots of Tg , Tx and Tx as a function of scanning rates of Fe-B9 BMG. Real Tg , Tx and Tx were extrapolated to the value at the heating rates of 0 K/s. (c) XRD patterns of Fe-B9 BMG alloy with diameters of 4 mm.
j m a t e r r e s t e c h n o l . 2 0 1 9;8(2):1907–1914
For investigating the thermoplastic deformation behavior of Fe-B9 BMG sample, several work temperatures within the SCL region (namely 873 K, 883 K, 893 K, 903 K) were selected for high temperature compression tests by a Hon-Ta mechanical test system with different strain rates (1 × 10−3 and 5 × 10−2 s−1 ). The compression testing was conducted on the as-cast specimens with a diameter and a height of 2 and 4 mm, respectively. For the accuracy, the both ends of samples were polished carefully to ensure parallelism and flatness. Finally, the hot-compressed samples were examined by Xray diffraction (XRD, Bruker D8A X-ray diffractometer) with monochromatic Cu-Ka radiation and transmission electron microscopy (TEM, JOEL FX2000) operated at 200 kV. TEM samples were sliced from the as-cast and the hot-compressed samples by using the focused ion beam system (FEI Versa 3D Dual Beam FIB, operated at 30 kV) with special care to minimize the ion damage to samples. The appearance of as-cast and hot-compressed sample was examined by using scanning electron microscopy (SEM, FEI Inspect F50, operated at 25 kV).
2.
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Fig. 2 – Cross sectional SEM images of as-cast Fe-B9 BMG sample; insert is the enlarged image.
Results and discussion
Before studying the thermoplastic deformation behavior of a Fe-B9 BMG rod, the amorphous state of the as-cast Fe-B9 alloy rod was examined by DSC and XRD analyses. The DSC scans of a Fe-B9 alloy sample with different heating rates exhibit the typical phase transformation behavior of a metallic glass. There is a clear glass transition, followed by a supercooled liquid region, and then an exothermic reaction due to crystallization, as shown in Fig. 1(a). According to the results of DSC and HTDSC analyses, the thermal properties of the Fe-B9 sample, including the real glass transition temperature (Tg ), real crystallization temperature (Tx ), supercooled liquid region (Tx ), liquidus temperature (Tl ), and GFA index ( and m , where = Tg /(Tg + Tl ) [30] and m = (2Tx − Tg )/Tl [31]), are summarized and listed in Table 1and Fig. 1(b). This Fe-B9 BMG has a good GFA ( and m are 0.405 and 0.699, respectively) as well as a large supercooled region (Tx = 74 K). The XRD pattern of the Fe-B9 alloy rod with a diameter of 4 mm is amorphous with only broadened and diffused humps in the 2 range of 35◦ –55◦ , as shown in Fig. 1(c). The results of both XRD and DSC analyses are evidence that the Fe-B9 alloy rods possess an amorphous structure with high GFA. However, in the as-cast sample, there is a small amount of micro-sized flower-like precipitates coexisting in the amorphous matrix (as shown in Fig. 2) by SEM, suggesting that there is a Y-rich compound via EDS analysis. The Y content in the precipitate (15.3 at. %) is much higher than that in the matrix (1.2 at. %). The selected area diffraction (SAD) patterns confirm that these precipitates are a CaC2 -structured YC2 compound (by TEM examination), as illustrated in Fig. 3. Because the Y element has a strong affinity with non-metallic elements (C, O, P and N), the impurity
Table 1 – Thermal properties of Fe-B9 BMG sample. Sample
Tg (K)
Tx (K)
Tx (K)
Tm (K)
Tl (K)
Fe-B9
832
906
74
1374
1419
0.405
m 0.699
can form stable compounds, leaving the remaining material as amorphous. Consequently, an enhanced glass formability of the alloy is achieved [32]. In this study, the Fe-based BMG used industrial ferrous-alloys. Therefore, the credited Y-rich compound in the matrix can be predicted. Since the Y-rich compound only occupies 0.77 vol.% of the matrix from statistical estimates of the volume fraction (the remaining 99.23 vol.% is amorphous), this crystalline phase could not be resolved by our XRD analysis. The thermoplastic deformation behavior of Fe-B9 BMG was investigated by the hot compression test at different temperatures (873 K, 883 K, 893 K, 903 K) with different strain rates (1 × 10−3 –5 × 10−2 s−1 ) in the SLC region. The true stress–strain curves of the BMG samples, deformed at different conditions, are summarized in Fig. 4 and Table 2 the stress–strain curves (especially for lower temperatures and higher strain rates) show a stress overshoot at the beginning of compression, and then reduce to a steady-state flow with increasing plastic strain. The stress overshoot and steady-state flow reduce systematically with a decreasing compressive strain rate and increasing compression temperature, as shown in Fig. 4. This can be explained by free volume theory [33]. The production rate of the free volume is proportional to the deformation amount and strain rate. In contrast, the degradation rate of the free volume is proportional to the environmental temperature and time. Due to the competition between the deformation-induced production of the free volume and the thermal annihilation, the stress overshoot shows non-Newtonian flow at the beginning of high-temperature compression in the SCL. Once a free volume has a large enough amount to influence strain softening, the stress value is reduced until the degradation rate of the free volume equals the production rate (equilibrium state). The lowest flow stress, 510 MPa, is obtained at 873–883 K with an initial strain rate of 2.5 × 10−3 s−1 for all hot compression conditions. During the compression test, more than 60% plastic strain is attained at the SCL region with strain rates of 2.5 × 10−3 –2.5 × 10–2 s−1 , as shown in Fig. 5.
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Fig. 3 – (a) TEM image from Fig. 2 of flower-like precipitate phase, and (b) B[013] of the micro-beam diffraction pattern (MBDP) of YC2 precipitate from (a).
The XRD results of the hot compressed samples reveal that the thermoplastic deformed samples remain in the amorphous state. The XRD patterns exhibit broadened and diffused humps in the 2 range of 30◦ –50◦ , and no apparent crystalline peaks can be detected, as shown in Fig. 6. A TEM analysis of the hot compressed sample at a higher temperature with a lower strain rate (at 903 K and 2.5 × 10−3 s−1 , respectively) shows a few submicron particles. They seem to form a new precipitate
(marked II) on the surface of the sharp-edged Y-rich precipitate (marked I), as two kinds of crystalline precipitates embedded in the glass matrix, as shown in Fig. 7. Precipitate I and Precipitate II were identified to be the CaC2 -structured YC2 and hexagonal-structured (Cr, Mo)B2 compounds by nanobeam electron diffraction patterns, as illustrated in Fig. 7(c) and (d). Precipitate II is presumed to be formed during the hot compression test. Following the previous arguments in [34],
Fig. 4 – True stress–strain curves of hot compression test for the Fe-B9 BMG samples at different temperatures with different strain rates.
j m a t e r r e s t e c h n o l . 2 0 1 9;8(2):1907–1914
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Table 2 – Flow stress (MPa) of Fe-B9 BMG samples under different hot compression test conditions. Temperature
873 K Fractured 1296 1144 754 511 560
883 K Fractured 984 982 725 509 Crystallized
893 K Fractured 914 803 709 693 Crystallized
903 K Fractured 864 766 603 Crystallized Crystallized
Yan et al. show that the mechanically induced crystallization behavior is related to the stress. It is possible for Fe-based BMG to induce a (Cr, Mo)B2 phase during the hot compression test. In addition, the YC2 precipitate provides a multitude of heterogeneous nucleation sites for precipitating the (Cr, Mo)B2 with a lower energy barrier of nucleation, as a shown in Fig. 7. Overall, the XRD analyses and TEM characterization confirm that the Fe-B9 BMG has good thermal stability during the hot compression test, except with a higher temperature and lower strain rate. For the viscous flow behavior of the Fe-B9 BMG, the Backofen equation is used [35]: flow = K˙εm
(1)
where flow is the flow stress, K is a constant, is the strain rate, and m is the strain rate sensitivity. Fig. 8 shows the plots of the flow stress (ln ) as a function of strain rate (ln) at different temperatures. The calculated m-values of strain rate sensitivity for Fe-B9 BMG are from 0.36 to 0.59. At a higher working temperature, the m-value is about 0.59, which is close to that for Newtonian flow, but gradually changes to non-Newtonian at a lower working temperature. This transition between non-Newtonian and Newtonian flow was also observed in several other BMG systems [15,16,36–38]. Following the previous definition [39,40], the 0.3–0.8 m-value is usually found in superplastic crystalline alloys, and an mvalue of 0.5 is commonly associated with excellent plasticity. The m-values of Fe-B9 BMG are similar to the m-values of the Cu-based (0.4–0.6) [41] and Zr-based (0.4–0.56) [15] BMGs. Although the minimum stress overshoot at a temperature from 873 to 883 K is 510 MPa, this is much higher than that of the Cu-based and Zr-based BMGs. The current Fe-B9 BMGs
Fig. 6 – XRD patterns of the as-cast and hot compressed Fe-B9 BMG samples at higher temperature conditions.
possess high m-values that are above 0.36–0.59 and have good superplasticity within the SCL region. Therefore, Fe-B9 BMG is believed to be a promising material for fabricating miniature industrial parts.
Fig. 5 – A representative photograph of the Fe-B9 BMG rods deformed at 873 K with a strain rate 5 × 10−2 s−1 ; (a) top view and (b) side view. In each picture, left side is the original specimen and right side is deformed specimen.
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Fig. 7 – (a) TEM image of the thermoplastic deformed Fe-B9 sample after hot compression test at 903 K and 5 × 10−2 s−1 ; (b) SADP of amorphous matrix, (c) B MBDP of YC2 precipitate (I), and (d) MBDP of crystallized (Cr, Mo) B2 phase (II).
3.
Conclusion
Based on the results of the DSC and XRD analyses, hot compression test, and TEM examination, the deformation behavior of Fe-B9 BMG within the SCL region can be summarized as follows.
Fig. 8 – Plots of the flow stress as a function of strain rate at different temperatures; insert is the m-value.
(1) The results of XRD and DSC analyses reveal that the FeB9 alloy rods possess an amorphous structure with good GFA ( and m are 0.405 and 0.699, respectively) and a large supercooled region (Tx = 74 K). However, SEM and TEM observations found a little amount of YC2 crystals co-existing with the amorphous matrix. The estimated amount is about 0.8 vol.% and is less than the resolution of a regular X-ray diffractometer. (2) The stress overshoot and steady-state flow reduce systematically with decreasing compressive strain rate and increasing compression temperature. The lowest flow
j m a t e r r e s t e c h n o l . 2 0 1 9;8(2):1907–1914
stress of 510 MPa is obtained at the test conditions of 873–883 K and 2.5 × 10−3 s−1 . (3) The thermoplastic deformed samples remain in their amorphous state (by XRD analysis). However, TEM characterization detected a few submicron hexagonal-structured (Cr, Mo)B2 particles at the surface of the pre-existing YC2 precipitate. This partial crystallization is attributed to the mechanically induced crystallization behavior during the hot compression test. (4) A strain rate sensitivity exponent (m) of 0.36–0.59 value can be obtained for the Fe-B9 BMG, deformed at a temperature of 873–903 K. This implies that Fe-B9 BMG behaves like a superplastic metal. Therefore, thermoplastic forming is a feasible method to fabricate complex-shaped miniature parts.
Conflicts of interest The authors declare no conflicts of interest.
Acknowledgement The authors like to gratefully acknowledge the sponsorship from the Ministry of Science and Technology of ROC under the project MOST 103-2221-E-008-028-MY3, MOST 103-2120M-110-004, and MOST 105-2918-I-008-001. The authors also like to acknowledge the valuable discuss on preparing this manuscript by Prof. T.S. Tsao, Department of Mechanical and Aerospace Engineering, and Prof. J.M. Yang, Department of Materials Science and Engineering, University of California Los Angles, USA.
references
[1] Lu ZP, Liu CT, Thompson JR, Porter WD. Structural amorphous steels. Phys Rev Lett 2004;92:245503. [2] Inoue A, Shen BL, Chang CT. Super-high strength of over 4000 MPa for Fe-based bulk glassy alloys in [(Fe1−x Cox )0.75 B0.2 Si0.05 ]96 Nb4 system. Acta Mater 2004;52:4093. [3] Lu ZP, Liu CT, Carmichael CA, Porter WD, Deevi SC. Bulk glass formation in an Fe-based Fe–Y–Zr–M (M = Cr, Co, Al)–Mo–B system. J Mater Res 2004;19:921. [4] Ponnambalam V, Poon SJ, Shiflet GJ. Fe-based bulk metallic glasses with diameter thickness larger than one centimeter. J Mater Res 2004;19:1320. [5] Guo SF, Qiu JL, Yu P, Xie SH, Chen W. Fe-based bulk metallic glasses: brittle or ductile? Appl Phys Lett 2014;105:161901. [6] Gu XJ, Poon SJ, Shiflet GJ. Effects of carbon content on the mechanical properties of amorphous steel alloys. Scripta Mater 2007;57:289. [7] Fang H, Hui X, Chen G. Effects of Mn addition on the magnetic property and corrosion resistance of bulk amorphous steels. J Alloys Comp 2008;464:292. [8] Wang YB, Li HF, Cheng Y, Wei SC, Zheng YF. Corrosion performances of a nickel-free Fe-based bulk metallic glass in simulated body fluids. Electrochem Commun 2009;11:2187. [9] Pang SJ, Zhang T, Asami K, Inoue A. Bulk glassy Fe–Cr–Mo–C–B alloys with high corrosion resistance. Corros Sci 2002;44:1847.
1913
[10] Long ZL, Shao Y, Deng XH, Zhang ZC, Jiang Y, Zhang P, et al. Cr effects on magnetic and corrosion properties of Fe–Co–Si–B–Nb–Cr bulk glassy alloys with high glass-forming ability. Intermetallics 2007;15:1453. [11] Tsai PH, Xiao AC, Li JB, Jang JSC, Chu JP, Huang JC. Prominent Fe-based bulk amorphous steel alloy with large supercooled liquid region and superior corrosion resistance. J Alloys Comp 2014;586:94. [12] Tsai PH, Lin YZ, Li JB, Jian SR, Jang JSC, Li C, et al. Sharpness improvement of surgical blade by means of ZrCuAlAgSi metallic glass and metallic glass thin film coating. Intermetallics 2012;31:127. [13] Jang JSC, Tsai PH, Shiao AZ, Li TH, Chen CY, Chu JP, et al. Enhanced cutting durability of surgical blade by coating with Fe-based metallic glass thin film. Intermetallics 2015;65: 56. [14] Tsai PH, Li TH, Hsu KT, Chiou JW, Jang JSC, Chu JP. Effect of coating thickness on the cutting sharpness and durability of Zr-based metallic glass thin film coated surgical blades. Thin Solid Films 2016;618:36. [15] Jang JSC, Chang CF, Huang YC, Huang JC, Chiang WJ, Liu CT. Viscous flow and microforming of a Zr-base bulk metallic glass. Intermetallics 2009;17:200. [16] Li JB, Zhang HZ, Jang JSC, Jian SR, Li C, Huang JC, et al. Viscous flow and thermoplastic forming ability of a Zr-based bulk metallic glass composite with Ta dispersoids. J Alloys Comp 2012;536:165. [17] Kumar G, Schroers J. Write and erase mechanisms for bulk metallic glass. Appl Phys Lett 2008;92:031901. [18] Schroers J, Pham Q, Peker A, Paton N, Curtis RV. Blow molding of bulk metallic glass. Scripta Mater 2007; 57:341. [19] Saotome Y, Okaniwa S, Kimura H, Inoue A. Superplastic nanoforging of Pt-based metallic glass with dies of Zr-BMG and glassy carbon fabricated by focused ion beam. Mater Sci Forum 2007;539–543:2088. [20] Schroers J. The superplastic forming of bulk metallic glasses. J Miner Met Mater Soc 2005;57:35. [21] Schroers J, Pham Q, Desai A. Thermoplastic forming of bulk metallic glass – a technology for MEMS and microstructure fabrication. J Microelectromech Syst 2007;16: 240. [22] Sharma P, Kaushik N, Kimura H, Saotome Y, Inoue A. Nano-fabrication with metallic glass-an exotic material for nano-electromechanical systems. Nanotechnology 2007;18:035302. [23] Kumar G, Tang HX, Schroers J. Nanomoulding with amorphous metals. Nature 2009;457:868. [24] Wang D, Liao G, Pan J, Tang Z, Peng P, Liu L, et al. Superplastic micro-forming of Zr65 Cu17.5 Ni10 Al7.5 bulk metallic glass with silicon mold using hot embossing technology. J Alloys Comp 2009;484:118. [25] Schroers J. Processing of bulk metallic glass. Adv Mater 2010;22:1566. [26] Wu C, Hu R, Man Q, Chang C, Wang X. Thermoplastic deformation of ferromagnetic CoFe-based bulk metallic glasses. Appl Phys A 2007;123:742. [27] Yiu P, Hsueh CH, Shek CH. Rapid thermoplastic formation of Fe-based metallic glass foil achieved by electropulsing. Mater Lett 2014;136:353. [28] Zhang W, Miao H, Li Y, Chang C, Xie G, Jia X. Glass-forming ability and thermoplastic formability of ferromagnetic (Fe, Co, Ni)75 P10 C10 B5 metallic glasses. J Alloys Comp 2017;707: 57. [29] Shen J, Chen Q, Sun J, Fan H, Wang G. Exceptionally high glass-forming ability of an FeCoCrMoCBY alloy. Appl Phys Lett 2005;86:151907.
1914
j m a t e r r e s t e c h n o l . 2 0 1 9;8(2):1907–1914
[30] Lu ZP, Liu CT. A new approach to understanding and measuring glass formation in bulk amorphous materials. Intermetallics 2004;12:1035. [31] Du XH, Huang JC, Liu CT, Lu ZP. New criterion of glass forming ability for bulk metallic glasses. J Appl Phys 2007;101:086108. [32] Yan M, Shen J, Zhang T, Zou J. Enhanced glass-forming ability of a Zr-based bulk metallic glass with yttrium doping. J Non-Cryst Solids 2006;352:3109. [33] Hey PD, Sietsma J, Beukel AVD. Structural disordering in amorphous Pd40 Ni40 P20 induced by high temperature deformation. Acta Mater 1998;46:5873. [34] Yan Z, Song K, Hu Y, Dai F, Chu Z, Eckert J. Localized crystallization in shear bands of a metallic glass. Scient Rep 2016;6:19358. [35] Nieh TG, Wadsworth J, Sherby OD. Superplasticity in metals and ceramics. Cambridge University Press 1997. [36] Song SX, Lai YH, Huang JC, Nieh TG. Homogeneous deformation of Au-based metallic glass micropillars in
[37] [38]
[39]
[40]
[41]
compression at elevated temperatures. Appl Phys Lett 2009;94:061911. Nieh TG, Wadsworth J. Homogeneous deformation of bulk metallic glasses. Scripta Mater 2006;54:387. Kato H, Kawamura Y, Inoue A, Chen HS. Newtonian to non-Newtonian master flow curves of a bulk glass alloy Pd40 Ni10 Cu30 P20 . Appl Phys Lett 1998;73:3665. Nieh TG, Mukai T, Liu CT, Wadsworth J. Superplastic behavior of a Zr–10Al–5Ti–17.9Cu–14.6Ni metallic glass in the supercooled liquid region. Scripta Mater 1999;40:1021. Chu JP, Chiang CL, Mahalingam T, Nieh TG. Plastic flow and tensile ductility of a bulk amorphous Zr55 Al10C u30 Ni5 alloy at 700 K. Scripta Mater 2003;49:435. Chiang CL, Chu JP, Lo CT, Nieh TG, Wang ZX, Wang WH. Homogeneous plastic deformation in a Cu-based bulk amorphous alloy. Intermetallics 2004;12:1057.
Available online at www.sciencedirect.com
www.jmrt.com.br
Original Article
Thermoplastic deformation behavior of a Fe-based bulk metallic glass within the supercooled liquid region S.M. Song a , Y.C. Liao b , T.H. Li a , C.K. Lee a , P.H. Tsai a , J.S.C. Jang a,b,∗ , J.C. Huang c,d a
Institute of Materials Science and Engineering, National Central University, Chung-Li, Taoyuan 320, Taiwan Department of Mechanical Engineering, National Central University, Chung-Li, Taoyuan 320, Taiwan c Department of Materials and Optoelectronic Science, Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan d Center for Advanced Study, City University of Hong Kong, Kowloon, Hong Kong Special Administrative Region b
a r t i c l e
i n f o
a b s t r a c t
Article history:
Fe41 Cr15 Co7 Mo14 C12 B9 Y2 (Fe-B9) bulk metallic glass (BMG) rods with high glass forming abil-
Received 27 July 2018
ity and large supercooled liquid (SCL) region were fabricated by arc melting and suction
Accepted 12 January 2019
casting. The amorphous state of these Fe-B9 BMG rods was ascertained by X-ray diffraction
Available online 19 February 2019
(XRD) and differential scanning calorimetry (DSC). The thermoplastic deformation behavior
Keywords:
(873 K, 883 K, 893 K, and 903 K in the SCL region) and strain rates (1 × 10−3 –5 × 10−2 s−1 ). The
of these BMG rods was studied by using the hot compression test at different temperatures Metallic glasses
results of the hot compression test reveal that the flow stress of Fe-B9 BMG reduces system-
Viscous flow
atically with increasing temperature and decreasing strain rate. Strain sensitivity exponent
Superplasticity
(m) values of the Fe-B9 BMG were calculated to be about 0.36–0.59 in the SCL region, indi-
Mechanical properties
cating that Fe-B9 BMG possesses superplasticity. Overall, the optimum working conditions of thermoplastic forming for Fe-B9 BMG can be achieved by compressively deforming the
Casting
sample with a constant strain rate of 2.5 × 10−3 s−1 at a temperature from 873 to 883 K. © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1.
Introduction
Fe-based bulk metallic glasses (BMGs), also called bulk amorphous steels, have attracted the attention of many scientists
∗
due to their unique properties, such as the ultrahigh hardness and fracture strength, superior wear resistance, excellent corrosion resistance, good magnetic properties, and higher thermal stability for engineering applications [1–10]. In addition, Fe-based BMG can be fabricated by using industrial raw materials (pig-iron and boron ferrous alloy), leading to a reduced production cost. Recently, some researchers have used Fe-based BMG to make surgical blades and apply a metallic glass thin film (MGTF) coating on the surgical blades.
Corresponding author. E-mail: [email protected] (J. Jang). https://doi.org/10.1016/j.jmrt.2019.01.007 2238-7854/© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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The edge-tip of both BMG-made and MGTF-coated blades is extremely flat. The surface roughness of the blade edge can decrease down to nanoscale due to the amorphous nature with no crystal defects. As a result, the cutting sharpness was enhanced significantly in comparison with commercial surgical blades [11–14]. In addition, the Fe-based BMG/MGTF blades exhibit much better cutting durability than the Zrbased BMG/MGTF blades [11] due to their ultrahigh hardness and superior wear resistance. Therefore, workers of amorphous alloys suggest that the Fe-based BMG can be a priority choice for surgical tools and other biomedical related parts. One of the most regarded features of metallic glasses is thermoplastic forming (TPF). This is typically carried out in the supercooled liquid region (SCL) between the glass transition temperature (Tg ) and the crystallization temperature (Tx ) where the metallic glass exhibits very low viscosity (∼107−8 Pa s) [15,16]. This TPF ability has been used for a wide range of applications, such as writing-erasing, blow molding, and surface embossing, particularly for complex-shaped micro-components of near-net-shape fabrication [16–25]. Febased BMGs do not easily form complex structures by traditional machine processing due to their ultrahigh hardness and relative brittleness compared with Zr-based BMGs. Therefore, the TPF process may be a good way to make the Fe-based BMG miniature parts for engineering and medical applications. Several Fe-based BMG TPF systems, such Co31 Fe31 Nb8 B30 [26], Fe78 B13 Si9 [27], Fe40 Co20 Ni15 P10 C10 B5 [28], have been developed. However, these alloys exhibit too low a glass-forming ability (GFA) to perform a TPF process for feasible engineering applications. In the literature, Fe41 Co7 Cr15 Mo14 C15 B6 Y2 BMG [29] was the first reported to have high GFA (critical size 16 mm), high fracture strength (3500 MPa), and ultrahigh hardness (1250 Hv). However, this Fe-based BMG exhibits a small SCL (Tx = 38 K), and is not easily used with TPF technology. Furthermore, by modifying the carbon/boron ratio from the previous Febased BMG, another Fe-based BMG, Fe41 Cr15 Co7 Mo14 C12 B9 Y2 (Fe-B9) with wide SCL (Tx = 81 K) has been explored [11]. This Fe-B9 BMG presents superior corrosion resistance in simulated body fluids, compared with 316 stainless steel. In this study, we investigate the thermoplastic deformation behavior of Fe41 Cr15 Co7 Mo14 C12 B9 Y2 BMG with industrial raw materials and characterize the process window of thermoplastic forming for further engineering applications.
1.1.
(XRD, Bruker D8A X-ray diffractometer) with monochromatic Cu-K␣ radiation. The XRD patterns were obtained from the central area of the BMG rods. Thermal analyses of the as-cast samples were carried out by differential scanning calorimeter (DSC, METTLER TOLEDO DSC 1) and high temperature differential scanning calorimeter (HTDSC, Netzsch STA449F3), respectively. The hardness of the specimens was measured by using a Vickers hardness tester (Mitutoyo, HM-220 Series 810) under a load of 2 kgf for 10 s.
Experimental procedure
The alloy ingots based on the compositions of Fe41 Cr15 Co7 Mo14 C12 B9 Y2 (Fe-B9) in atomic percentage were first prepared by arc melting of the appropriate mixture of ferrous alloys and pure elements, such as pig iron (94.2 wt.% Fe, 4.6 wt.% C, 1 wt.% Si, 0.2 wt.% P), ferro-boron (77.45 wt.% Fe, 21 wt.% B, 0.55 wt.% C), Cr3 C2 , Cr, Co, Mo, Fe, and Y (purity > 99%) under a Ti-gettered argon atmosphere. The ingots were re-melted at four times in the arc-melting furnace under purified argon atmosphere to ensure their homogeneity. Sample rods with a diameter of 2–4 mm were produced by suction-cast into the water-cooling Cu mold under a high purity Ar atmosphere. Amorphous state of the BMG rods was ascertained by X-ray diffraction analysis
Fig. 1 – (a) DSC scans of Fe-B9 BMG sample with different scanning rates, (b) Plots of Tg , Tx and Tx as a function of scanning rates of Fe-B9 BMG. Real Tg , Tx and Tx were extrapolated to the value at the heating rates of 0 K/s. (c) XRD patterns of Fe-B9 BMG alloy with diameters of 4 mm.
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For investigating the thermoplastic deformation behavior of Fe-B9 BMG sample, several work temperatures within the SCL region (namely 873 K, 883 K, 893 K, 903 K) were selected for high temperature compression tests by a Hon-Ta mechanical test system with different strain rates (1 × 10−3 and 5 × 10−2 s−1 ). The compression testing was conducted on the as-cast specimens with a diameter and a height of 2 and 4 mm, respectively. For the accuracy, the both ends of samples were polished carefully to ensure parallelism and flatness. Finally, the hot-compressed samples were examined by Xray diffraction (XRD, Bruker D8A X-ray diffractometer) with monochromatic Cu-Ka radiation and transmission electron microscopy (TEM, JOEL FX2000) operated at 200 kV. TEM samples were sliced from the as-cast and the hot-compressed samples by using the focused ion beam system (FEI Versa 3D Dual Beam FIB, operated at 30 kV) with special care to minimize the ion damage to samples. The appearance of as-cast and hot-compressed sample was examined by using scanning electron microscopy (SEM, FEI Inspect F50, operated at 25 kV).
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Fig. 2 – Cross sectional SEM images of as-cast Fe-B9 BMG sample; insert is the enlarged image.
Results and discussion
Before studying the thermoplastic deformation behavior of a Fe-B9 BMG rod, the amorphous state of the as-cast Fe-B9 alloy rod was examined by DSC and XRD analyses. The DSC scans of a Fe-B9 alloy sample with different heating rates exhibit the typical phase transformation behavior of a metallic glass. There is a clear glass transition, followed by a supercooled liquid region, and then an exothermic reaction due to crystallization, as shown in Fig. 1(a). According to the results of DSC and HTDSC analyses, the thermal properties of the Fe-B9 sample, including the real glass transition temperature (Tg ), real crystallization temperature (Tx ), supercooled liquid region (Tx ), liquidus temperature (Tl ), and GFA index ( and m , where = Tg /(Tg + Tl ) [30] and m = (2Tx − Tg )/Tl [31]), are summarized and listed in Table 1and Fig. 1(b). This Fe-B9 BMG has a good GFA ( and m are 0.405 and 0.699, respectively) as well as a large supercooled region (Tx = 74 K). The XRD pattern of the Fe-B9 alloy rod with a diameter of 4 mm is amorphous with only broadened and diffused humps in the 2 range of 35◦ –55◦ , as shown in Fig. 1(c). The results of both XRD and DSC analyses are evidence that the Fe-B9 alloy rods possess an amorphous structure with high GFA. However, in the as-cast sample, there is a small amount of micro-sized flower-like precipitates coexisting in the amorphous matrix (as shown in Fig. 2) by SEM, suggesting that there is a Y-rich compound via EDS analysis. The Y content in the precipitate (15.3 at. %) is much higher than that in the matrix (1.2 at. %). The selected area diffraction (SAD) patterns confirm that these precipitates are a CaC2 -structured YC2 compound (by TEM examination), as illustrated in Fig. 3. Because the Y element has a strong affinity with non-metallic elements (C, O, P and N), the impurity
Table 1 – Thermal properties of Fe-B9 BMG sample. Sample
Tg (K)
Tx (K)
Tx (K)
Tm (K)
Tl (K)
Fe-B9
832
906
74
1374
1419
0.405
m 0.699
can form stable compounds, leaving the remaining material as amorphous. Consequently, an enhanced glass formability of the alloy is achieved [32]. In this study, the Fe-based BMG used industrial ferrous-alloys. Therefore, the credited Y-rich compound in the matrix can be predicted. Since the Y-rich compound only occupies 0.77 vol.% of the matrix from statistical estimates of the volume fraction (the remaining 99.23 vol.% is amorphous), this crystalline phase could not be resolved by our XRD analysis. The thermoplastic deformation behavior of Fe-B9 BMG was investigated by the hot compression test at different temperatures (873 K, 883 K, 893 K, 903 K) with different strain rates (1 × 10−3 –5 × 10−2 s−1 ) in the SLC region. The true stress–strain curves of the BMG samples, deformed at different conditions, are summarized in Fig. 4 and Table 2 the stress–strain curves (especially for lower temperatures and higher strain rates) show a stress overshoot at the beginning of compression, and then reduce to a steady-state flow with increasing plastic strain. The stress overshoot and steady-state flow reduce systematically with a decreasing compressive strain rate and increasing compression temperature, as shown in Fig. 4. This can be explained by free volume theory [33]. The production rate of the free volume is proportional to the deformation amount and strain rate. In contrast, the degradation rate of the free volume is proportional to the environmental temperature and time. Due to the competition between the deformation-induced production of the free volume and the thermal annihilation, the stress overshoot shows non-Newtonian flow at the beginning of high-temperature compression in the SCL. Once a free volume has a large enough amount to influence strain softening, the stress value is reduced until the degradation rate of the free volume equals the production rate (equilibrium state). The lowest flow stress, 510 MPa, is obtained at 873–883 K with an initial strain rate of 2.5 × 10−3 s−1 for all hot compression conditions. During the compression test, more than 60% plastic strain is attained at the SCL region with strain rates of 2.5 × 10−3 –2.5 × 10–2 s−1 , as shown in Fig. 5.
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Fig. 3 – (a) TEM image from Fig. 2 of flower-like precipitate phase, and (b) B[013] of the micro-beam diffraction pattern (MBDP) of YC2 precipitate from (a).
The XRD results of the hot compressed samples reveal that the thermoplastic deformed samples remain in the amorphous state. The XRD patterns exhibit broadened and diffused humps in the 2 range of 30◦ –50◦ , and no apparent crystalline peaks can be detected, as shown in Fig. 6. A TEM analysis of the hot compressed sample at a higher temperature with a lower strain rate (at 903 K and 2.5 × 10−3 s−1 , respectively) shows a few submicron particles. They seem to form a new precipitate
(marked II) on the surface of the sharp-edged Y-rich precipitate (marked I), as two kinds of crystalline precipitates embedded in the glass matrix, as shown in Fig. 7. Precipitate I and Precipitate II were identified to be the CaC2 -structured YC2 and hexagonal-structured (Cr, Mo)B2 compounds by nanobeam electron diffraction patterns, as illustrated in Fig. 7(c) and (d). Precipitate II is presumed to be formed during the hot compression test. Following the previous arguments in [34],
Fig. 4 – True stress–strain curves of hot compression test for the Fe-B9 BMG samples at different temperatures with different strain rates.
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Table 2 – Flow stress (MPa) of Fe-B9 BMG samples under different hot compression test conditions. Temperature
873 K Fractured 1296 1144 754 511 560
883 K Fractured 984 982 725 509 Crystallized
893 K Fractured 914 803 709 693 Crystallized
903 K Fractured 864 766 603 Crystallized Crystallized
Yan et al. show that the mechanically induced crystallization behavior is related to the stress. It is possible for Fe-based BMG to induce a (Cr, Mo)B2 phase during the hot compression test. In addition, the YC2 precipitate provides a multitude of heterogeneous nucleation sites for precipitating the (Cr, Mo)B2 with a lower energy barrier of nucleation, as a shown in Fig. 7. Overall, the XRD analyses and TEM characterization confirm that the Fe-B9 BMG has good thermal stability during the hot compression test, except with a higher temperature and lower strain rate. For the viscous flow behavior of the Fe-B9 BMG, the Backofen equation is used [35]: flow = K˙εm
(1)
where flow is the flow stress, K is a constant, is the strain rate, and m is the strain rate sensitivity. Fig. 8 shows the plots of the flow stress (ln ) as a function of strain rate (ln) at different temperatures. The calculated m-values of strain rate sensitivity for Fe-B9 BMG are from 0.36 to 0.59. At a higher working temperature, the m-value is about 0.59, which is close to that for Newtonian flow, but gradually changes to non-Newtonian at a lower working temperature. This transition between non-Newtonian and Newtonian flow was also observed in several other BMG systems [15,16,36–38]. Following the previous definition [39,40], the 0.3–0.8 m-value is usually found in superplastic crystalline alloys, and an mvalue of 0.5 is commonly associated with excellent plasticity. The m-values of Fe-B9 BMG are similar to the m-values of the Cu-based (0.4–0.6) [41] and Zr-based (0.4–0.56) [15] BMGs. Although the minimum stress overshoot at a temperature from 873 to 883 K is 510 MPa, this is much higher than that of the Cu-based and Zr-based BMGs. The current Fe-B9 BMGs
Fig. 6 – XRD patterns of the as-cast and hot compressed Fe-B9 BMG samples at higher temperature conditions.
possess high m-values that are above 0.36–0.59 and have good superplasticity within the SCL region. Therefore, Fe-B9 BMG is believed to be a promising material for fabricating miniature industrial parts.
Fig. 5 – A representative photograph of the Fe-B9 BMG rods deformed at 873 K with a strain rate 5 × 10−2 s−1 ; (a) top view and (b) side view. In each picture, left side is the original specimen and right side is deformed specimen.
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Fig. 7 – (a) TEM image of the thermoplastic deformed Fe-B9 sample after hot compression test at 903 K and 5 × 10−2 s−1 ; (b) SADP of amorphous matrix, (c) B MBDP of YC2 precipitate (I), and (d) MBDP of crystallized (Cr, Mo) B2 phase (II).
3.
Conclusion
Based on the results of the DSC and XRD analyses, hot compression test, and TEM examination, the deformation behavior of Fe-B9 BMG within the SCL region can be summarized as follows.
Fig. 8 – Plots of the flow stress as a function of strain rate at different temperatures; insert is the m-value.
(1) The results of XRD and DSC analyses reveal that the FeB9 alloy rods possess an amorphous structure with good GFA ( and m are 0.405 and 0.699, respectively) and a large supercooled region (Tx = 74 K). However, SEM and TEM observations found a little amount of YC2 crystals co-existing with the amorphous matrix. The estimated amount is about 0.8 vol.% and is less than the resolution of a regular X-ray diffractometer. (2) The stress overshoot and steady-state flow reduce systematically with decreasing compressive strain rate and increasing compression temperature. The lowest flow
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stress of 510 MPa is obtained at the test conditions of 873–883 K and 2.5 × 10−3 s−1 . (3) The thermoplastic deformed samples remain in their amorphous state (by XRD analysis). However, TEM characterization detected a few submicron hexagonal-structured (Cr, Mo)B2 particles at the surface of the pre-existing YC2 precipitate. This partial crystallization is attributed to the mechanically induced crystallization behavior during the hot compression test. (4) A strain rate sensitivity exponent (m) of 0.36–0.59 value can be obtained for the Fe-B9 BMG, deformed at a temperature of 873–903 K. This implies that Fe-B9 BMG behaves like a superplastic metal. Therefore, thermoplastic forming is a feasible method to fabricate complex-shaped miniature parts.
Conflicts of interest The authors declare no conflicts of interest.
Acknowledgement The authors like to gratefully acknowledge the sponsorship from the Ministry of Science and Technology of ROC under the project MOST 103-2221-E-008-028-MY3, MOST 103-2120M-110-004, and MOST 105-2918-I-008-001. The authors also like to acknowledge the valuable discuss on preparing this manuscript by Prof. T.S. Tsao, Department of Mechanical and Aerospace Engineering, and Prof. J.M. Yang, Department of Materials Science and Engineering, University of California Los Angles, USA.
references
[1] Lu ZP, Liu CT, Thompson JR, Porter WD. Structural amorphous steels. Phys Rev Lett 2004;92:245503. [2] Inoue A, Shen BL, Chang CT. Super-high strength of over 4000 MPa for Fe-based bulk glassy alloys in [(Fe1−x Cox )0.75 B0.2 Si0.05 ]96 Nb4 system. Acta Mater 2004;52:4093. [3] Lu ZP, Liu CT, Carmichael CA, Porter WD, Deevi SC. Bulk glass formation in an Fe-based Fe–Y–Zr–M (M = Cr, Co, Al)–Mo–B system. J Mater Res 2004;19:921. [4] Ponnambalam V, Poon SJ, Shiflet GJ. Fe-based bulk metallic glasses with diameter thickness larger than one centimeter. J Mater Res 2004;19:1320. [5] Guo SF, Qiu JL, Yu P, Xie SH, Chen W. Fe-based bulk metallic glasses: brittle or ductile? Appl Phys Lett 2014;105:161901. [6] Gu XJ, Poon SJ, Shiflet GJ. Effects of carbon content on the mechanical properties of amorphous steel alloys. Scripta Mater 2007;57:289. [7] Fang H, Hui X, Chen G. Effects of Mn addition on the magnetic property and corrosion resistance of bulk amorphous steels. J Alloys Comp 2008;464:292. [8] Wang YB, Li HF, Cheng Y, Wei SC, Zheng YF. Corrosion performances of a nickel-free Fe-based bulk metallic glass in simulated body fluids. Electrochem Commun 2009;11:2187. [9] Pang SJ, Zhang T, Asami K, Inoue A. Bulk glassy Fe–Cr–Mo–C–B alloys with high corrosion resistance. Corros Sci 2002;44:1847.
1913
[10] Long ZL, Shao Y, Deng XH, Zhang ZC, Jiang Y, Zhang P, et al. Cr effects on magnetic and corrosion properties of Fe–Co–Si–B–Nb–Cr bulk glassy alloys with high glass-forming ability. Intermetallics 2007;15:1453. [11] Tsai PH, Xiao AC, Li JB, Jang JSC, Chu JP, Huang JC. Prominent Fe-based bulk amorphous steel alloy with large supercooled liquid region and superior corrosion resistance. J Alloys Comp 2014;586:94. [12] Tsai PH, Lin YZ, Li JB, Jian SR, Jang JSC, Li C, et al. Sharpness improvement of surgical blade by means of ZrCuAlAgSi metallic glass and metallic glass thin film coating. Intermetallics 2012;31:127. [13] Jang JSC, Tsai PH, Shiao AZ, Li TH, Chen CY, Chu JP, et al. Enhanced cutting durability of surgical blade by coating with Fe-based metallic glass thin film. Intermetallics 2015;65: 56. [14] Tsai PH, Li TH, Hsu KT, Chiou JW, Jang JSC, Chu JP. Effect of coating thickness on the cutting sharpness and durability of Zr-based metallic glass thin film coated surgical blades. Thin Solid Films 2016;618:36. [15] Jang JSC, Chang CF, Huang YC, Huang JC, Chiang WJ, Liu CT. Viscous flow and microforming of a Zr-base bulk metallic glass. Intermetallics 2009;17:200. [16] Li JB, Zhang HZ, Jang JSC, Jian SR, Li C, Huang JC, et al. Viscous flow and thermoplastic forming ability of a Zr-based bulk metallic glass composite with Ta dispersoids. J Alloys Comp 2012;536:165. [17] Kumar G, Schroers J. Write and erase mechanisms for bulk metallic glass. Appl Phys Lett 2008;92:031901. [18] Schroers J, Pham Q, Peker A, Paton N, Curtis RV. Blow molding of bulk metallic glass. Scripta Mater 2007; 57:341. [19] Saotome Y, Okaniwa S, Kimura H, Inoue A. Superplastic nanoforging of Pt-based metallic glass with dies of Zr-BMG and glassy carbon fabricated by focused ion beam. Mater Sci Forum 2007;539–543:2088. [20] Schroers J. The superplastic forming of bulk metallic glasses. J Miner Met Mater Soc 2005;57:35. [21] Schroers J, Pham Q, Desai A. Thermoplastic forming of bulk metallic glass – a technology for MEMS and microstructure fabrication. J Microelectromech Syst 2007;16: 240. [22] Sharma P, Kaushik N, Kimura H, Saotome Y, Inoue A. Nano-fabrication with metallic glass-an exotic material for nano-electromechanical systems. Nanotechnology 2007;18:035302. [23] Kumar G, Tang HX, Schroers J. Nanomoulding with amorphous metals. Nature 2009;457:868. [24] Wang D, Liao G, Pan J, Tang Z, Peng P, Liu L, et al. Superplastic micro-forming of Zr65 Cu17.5 Ni10 Al7.5 bulk metallic glass with silicon mold using hot embossing technology. J Alloys Comp 2009;484:118. [25] Schroers J. Processing of bulk metallic glass. Adv Mater 2010;22:1566. [26] Wu C, Hu R, Man Q, Chang C, Wang X. Thermoplastic deformation of ferromagnetic CoFe-based bulk metallic glasses. Appl Phys A 2007;123:742. [27] Yiu P, Hsueh CH, Shek CH. Rapid thermoplastic formation of Fe-based metallic glass foil achieved by electropulsing. Mater Lett 2014;136:353. [28] Zhang W, Miao H, Li Y, Chang C, Xie G, Jia X. Glass-forming ability and thermoplastic formability of ferromagnetic (Fe, Co, Ni)75 P10 C10 B5 metallic glasses. J Alloys Comp 2017;707: 57. [29] Shen J, Chen Q, Sun J, Fan H, Wang G. Exceptionally high glass-forming ability of an FeCoCrMoCBY alloy. Appl Phys Lett 2005;86:151907.
1914
j m a t e r r e s t e c h n o l . 2 0 1 9;8(2):1907–1914
[30] Lu ZP, Liu CT. A new approach to understanding and measuring glass formation in bulk amorphous materials. Intermetallics 2004;12:1035. [31] Du XH, Huang JC, Liu CT, Lu ZP. New criterion of glass forming ability for bulk metallic glasses. J Appl Phys 2007;101:086108. [32] Yan M, Shen J, Zhang T, Zou J. Enhanced glass-forming ability of a Zr-based bulk metallic glass with yttrium doping. J Non-Cryst Solids 2006;352:3109. [33] Hey PD, Sietsma J, Beukel AVD. Structural disordering in amorphous Pd40 Ni40 P20 induced by high temperature deformation. Acta Mater 1998;46:5873. [34] Yan Z, Song K, Hu Y, Dai F, Chu Z, Eckert J. Localized crystallization in shear bands of a metallic glass. Scient Rep 2016;6:19358. [35] Nieh TG, Wadsworth J, Sherby OD. Superplasticity in metals and ceramics. Cambridge University Press 1997. [36] Song SX, Lai YH, Huang JC, Nieh TG. Homogeneous deformation of Au-based metallic glass micropillars in
[37] [38]
[39]
[40]
[41]
compression at elevated temperatures. Appl Phys Lett 2009;94:061911. Nieh TG, Wadsworth J. Homogeneous deformation of bulk metallic glasses. Scripta Mater 2006;54:387. Kato H, Kawamura Y, Inoue A, Chen HS. Newtonian to non-Newtonian master flow curves of a bulk glass alloy Pd40 Ni10 Cu30 P20 . Appl Phys Lett 1998;73:3665. Nieh TG, Mukai T, Liu CT, Wadsworth J. Superplastic behavior of a Zr–10Al–5Ti–17.9Cu–14.6Ni metallic glass in the supercooled liquid region. Scripta Mater 1999;40:1021. Chu JP, Chiang CL, Mahalingam T, Nieh TG. Plastic flow and tensile ductility of a bulk amorphous Zr55 Al10C u30 Ni5 alloy at 700 K. Scripta Mater 2003;49:435. Chiang CL, Chu JP, Lo CT, Nieh TG, Wang ZX, Wang WH. Homogeneous plastic deformation in a Cu-based bulk amorphous alloy. Intermetallics 2004;12:1057.