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Hydrogen-induced high damping of bulk metallic glasses
Materials Science and Engineering A 521–522 (2009) 354–358
Contents lists available at ScienceDirect
Materials Science and Engineering A journal homepage: www.elsevier.com/locate/msea
Hydrogen-induced high damping of bulk metallic glasses M. Hasegawa Department of Materials Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
a r t i c l e
i n f o
Article history: Received 30 June 2008 Accepted 8 October 2008 Keywords: Local structure Interstitial site Internal friction Hydrogen Metallic glass Compressive strength
a b s t r a c t There are two important topics concerned with the recent researches on the damping materials of hydrogenated metallic glasses (HMGs). One is the mechanism of the high hydrogen-induced internal friction of HMGs. The other is the materials processing of “bulk” HMGs for engineering. This article describes the summary of our recent studies on these topics. The first one is closely related to the local structure of the metallic glasses. Therefore, our recent results on the intermediate-range local structure of the simple two Zr-based metallic glasses are described, which has been clarified by the Voronoi analysis using the experimental data of the neutron diffraction measurements. The hydrogen-induced internal friction of HMGs is also discussed on the basis of these recent results of the local structure of the metallic glasses. In terms of the second topic, the first successful preparation of heavily hydrogenated Zr-based bulk HMG rods without hydrogen-induced surface embrittlement is described. They are prepared by a powdercompact-melting and liquid-casting process using Zr–Al–Ni–Cu metallic glass and ZrH2 powders as the starting materials. It has been found that they have high damping properties. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Metallic glasses can be prepared in bulk form and have high mechanical strength as well as high corrosion resistance [1,2]. Since these are key materials characteristics, metallic glasses may become more widely used. Most metallic glasses contain some alloying elements that have high affinity for hydrogen such as Zr, Ti, Hf, Mg and rare earth elements. Thus, metallic glasses can readily absorb hydrogen. Hydrogenated metallic glasses (HMGs) can be used as damping materials since they have high mechanical strength and exhibit high internal friction due to re-ordering of the hydrogen. Although there have been many reports on the hydrogen-induced internal friction of HMGs [3–18], there are still two important aspects that need to be investigated. One is the mechanism of the high hydrogen-induced internal friction of HMGs. The other is the processing of “bulk” HMGs to be used as engineering high damping materials. This article describes the summary of our recent studies on these two aspects [19–21]. The first aspect is closely related to the local structure of the bulk metallic glasses because the hydrogen atoms, which induce internal friction, occupy interstitial sites in the local structure of the metallic glasses. Accordingly, it is important to clarify the energy distribution of the interstitial sites for hydrogen in the glassy structure to discuss the hydrogen-induced internal friction. We have recently clarified the intermediate-range local structure of the two
E-mail address: [email protected]. 0921-5093/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2008.10.078
simple Zr66.7 Ni33.3 and Zr66.7 Cu33.3 metallic glasses by the Voronoi analysis using experimental data of neutron diffraction measurements [19]. An analysis of Voronoi polyhedra in the Reverse Monte Carlo (RMC) simulations based on the diffraction data makes it possible to characterize the atomic configurations around the constituent atoms. The RMC modeling [23] has been recognized to be an excellent method for visualizing the three-dimensional atomic arrangement of liquid and amorphous materials, based on the results of diffraction experiments. In this article the hydrogeninduced internal friction of HMGs will be discussed briefly on the basis of these recent results of the intermediate-range local structure of the metallic glasses. The other recent important aspect is the materials processing of “bulk” HMGs for engineering. The electrochemical technique is currently the most popular method of hydrogenating metallic glasses. There are many reports on the hydrogen-induced internal friction of metallic glasses hydrogenated by this technique [3–18]. However, they only report the results on hydrogenated metallic glass “ribbon” samples with a thickness of ∼20 m. When one tries to introduce a high amount of hydrogen into the bulk metallic glass by the electrochemical technique, the sample usually deforms and its surface peels off [23]. This is why the ribbon samples were used to investigate hydrogen-induced internal friction in the labbased studies. However, it is extremely important to prepare and study “bulky” hydrogenated metallic glasses in order to use them as engineering high-damping materials. We were the first to successfully investigate the temperature dependence of hydrogen-induced internal friction of “bulky” hydrogenated Zr-based metallic glasses in the form of rods of 1.5 mm diameter [13,14]. However, the hydro-
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gen content of the rod was only about 2 at.%. Recently, we have succeeded in preparing heavily hydrogenated Zr-based bulk metallic glasses for the first time by a powder-compact-melting and liquid-casting process. We used Zr–Al–Ni–Cu metallic glass and ZrH powders as the starting materials which had earlier been developed by us to prepare Zr-based glassy composite alloys containing dispersed crystalline ZrN [24]. In this article, the results of the hydrogen-induced internal friction and mechanical properties of heavily hydrogenated Zr–Al–Ni–Cu bulk metallic glass will be reported. 2. Interstitial site for hydrogen in metallic glass Metallic glass ribbons were synthesized by rapid quenching from the molten state using a single roller technique under Ar gas atmosphere. The neutron diffraction experiment was carried out using the High Intensity Total scattering spectrometer HIT-II at the High Energy Accelerator Research Organization (KEK), Tsukuba, Japan. Time-of-flight neutron diffraction using a spallation neutron source makes it possible to measure S(Q) over a wide Q range (from QZ5 nmK1 up to 200 nmK1 in this case), leading to a high resolution in real-space. The Reverse Monte Carlo (RMC) modeling [22] is a simple variant of the standard Monte Carlo procedure, which provides a powerful method for deriving three-dimensional simulations of the atomic arrangements of disordered materials. The local atomic environment for the simulations was characterized by means of a Voronoi analysis [25]. The distribution of the Voronoi polyhedra is expressed in terms of Schlafli notation where a polyhedron is denoted by a set of indices n3, n4, n5, n6, n7, n8, where ni is the number of faces with i vertices. The details of the experimental procedure and data analysis were described elsewhere [19]. The polyhedral environment in the RMC simulations of the Zr66.7 Ni33.3 and Zr66.7 Cu33.3 metallic glasses was investigated by means of a Voronoi analysis, in which the Voronoi polyhedra around Ni, Cu and Zr atoms were analyzed independently [19]. Although the detailed results of the analyses are not described in this article, what should be pointed out here again is that the Voronoi polyhedron analysis is powerful to understand the distribution fraction of the polyhedron in the structure of the metallic glass. Therefore, we have also applied the Voronoi analysis to clarify the tetrahedron in these Zr66.7 Ni33.3 and Zr66.7 Cu33.3 metallic glasses [20] because the polyhedrons concerned with the hydrogen-induced internal friction of Zr-based HMGs are tetrahedrons containing Zr which has a high affinity for hydrogen, i.e. 4Zr, 3Zr + 1 M, 2Zr + 2 M and 1Zr + 3 M (M = Ni or Cu). Fig. 1 shows the fraction of the 4Zr, 3Zr + 1 M, 2Zr + 2 M and 1Zr + 3 M tetrahedrons. It is found that the fraction of the Zr-rich tetrahedrons in the Zr66.7 Ni33.3 metallic glass is larger than that in the Zr66.7 Cu33.3 one. This means that the interstitial site distribution for hydrogen as a function of site energy is different from each other. Since the interstitial site distribution for hydrogen is directly related to the re-ordering of hydrogen atoms, which leads to the hydrogen-induced internal friction, it is expected that the temperature dependence of the internal friction is also different from each other. Therefore, it is extremely interesting to measure the temperature dependence of the hydrogen-induced internal friction of these Zr66.7 Ni33.3 and Zr66.7 Cu33.3 metallic glasses and to compare the results with data in Fig. 1. 3. Bulk hydrogenated metallic glass Alloy ingots of Zr53 Al11 Ni5 Cu31 were prepared in an arc-melting furnace in a purified argon atmosphere. The metallic glass powder was prepared by a conventional spray method in a purified argon atmosphere. Rod samples were prepared by a conventional copper-mold cast method in a purified argon atmosphere using
Fig. 1. Fraction of the 4Zr, 3Zr + 1 M, 2Zr + 2 M and 1Zr + 3 M (M = Ni or Cu) tetrahedrons of the Zr66.7 Ni33.3 (closed) and Zr66.7 Cu33.3 (open) metallic glasses.
a compacted mixture of the metallic glass and ZrH powders. The mass fraction of the starting ZrH powder was 4.8 mass%, with an expected final composition of (Zr55 Al10 Ni5 Cu30 )-H. The morphology of the sample and its surface were examined using a SEM. Chemical composition was analyzed using an SEM-EDX. Phases of the sample were identified by an X-ray diffraction method using monochromatized Cu-K␣ radiation. Thermal stability was investigated by DSC in a flowing purified argon atmosphere. The heating rate during the measurement was about 0.67 K/s. The hydrogen content of the samples was determined using an inert gas carrier melting thermal conductivity method. The internal friction measurements were carried out using a reed method over the temperature range of ∼90 to ∼380 K while under vacuum (∼10−2 Pa). The internal friction was measured using a resonance oscillation method at a frequency of ∼600 Hz. The strain amplitude was ∼1.0 × 10−5 . Details of the instrumental setup and measurement procedures have been described elsewhere [14]. Mechanical properties were estimated by measuring tensile or compression strength using an Instron testing machine and Vickers hardness. Straight cylindrical rods with a diameter of 1.0 and 1.5 mm and a length of about 50 mm were obtained. The hydrogen content of each rod was determined to be 7.0 and 7.3 at.%, respectively. This is about three times higher than the earlier reported hydrogen content of the Zr-based bulk metallic glass rod introduced by the electrochemical technique [13,14]. The analyzed composition of the alloy was Zr55 Al10 Ni5 Cu30 , as expected. SEM images of HMG rods reveal a smooth and shiny surface (Fig. 2). Fig. 2(b) shows SEM images of the surface of an HMG rod with a diameter of 1.5 mm. It should be noted that there are no cracks on the surface. Therefore, their morphology is the same as that of non-hydrogenated metallic glass and is completely different from that of rods hydrogenated by the electrochemical technique. Fig. 3 shows a cross-section of the X-ray diffraction pattern of rods with a diameter of 1.0 and 1.5 mm. The pattern was composed of only halo patterns, indicating that the prepared rod alloys were composed only of the amorphous phase. Fig. 4 shows DSC curves of the HMG rods with diameters of 1.0 and 1.5 mm; they show a small endothermic peak preceding a large exothermic peak, corresponding to a supercooled liquid and crystallization region, respectively. This indicates that the prepared amorphous rods are glassy. The
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Fig. 4. DSC curves of HMG rods with diameters of 1.0 and 1.5 mm.
Fig. 2. SEM images of hydrogenated Zr55 Al10 Ni5 Cu30 glass alloy rod with a diameter of 1.5 mm prepared by a powder-compact-melting and liquid-casting process using Zr–Al–Ni–Cu metallic glass and ZrH powders as the starting materials: (a) rod sample and (b) surface.
glass transition and crystallization temperatures, Tg and Tx , and the supercooled liquid region (Tx = Tx − Tg ) are summarized in Table 1. Data of the non-hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass are also listed for comparison [26]. The values for HMG rods with diameters of 1.0 and 1.5 mm are almost the same. This finding is consistent with the results of their hydrogen content analysis above. It should be noted that these values are different from those of the non-hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass rod even though their analyzed compositions are the same. This is attributable to interstitial hydrogen in the Zr–Al–Ni–Cu metallic glass. That is to say, the interstitial hydrogen decreases the glass forming ability by decreasing Tx . Fig. 5 shows the temperature dependence of the internal friction of HMG rods with a diameter of 1.0 and 1.5 mm. Both HMG rods show a broad internal friction peak at ∼273 K with peak values of ∼8 × 10−3 . It should be noted that their peak values are almost the same. This is consistent with their nearly identical hydrogen contents. Yagi et al. reported that the hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass ribbon absorbing about 6 at.%H showed an internal friction peak of ∼7 × 10−3 at ∼273 K [4]. The results of the present study are consistent with this report. Therefore, it is concluded that heavily and homogeneously hydrogenated Zr-based bulky metallic glass rods can be prepared by the powder-compact-melting and liquid-casting process as in this study. Fig. 6 shows the compressive stress–strain curve of the hydrogen loaded and hydrogen free Zr55 Al10 Ni5 Cu30 metallic glass rod of 1.5 mm diameter. Their mechanical properties and internal friction are summarized in Table 2. The compression fracture strength of the HMG rod was about 1.8 GPa, almost the same as that of the H free material. This indicates that interstitial hydrogen (∼7 at.%H) in Table 1 Thermal stability parameters of hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass prepared by a powder-compact-melting and liquid-casting process. Included in the table are data for non-hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass. Tg , glass transition temperature; Tx , crystallization temperatures, Tx = Tx − Tg , supercooling region.
Fig. 3. X-ray diffraction pattern of a cross-section of HMG rods with diameters of 1.0 and 1.5 mm.
Metallic glass
Tg (K)
Tx (K)
Tx (K)
HMG rod (1.0 mm diameter) HMG rod (1.5 mm diameter) Non-hydrogenated metallic glass rod
697 697 683
755 757 767
58 60 84
This study This study Ref. [26]
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Table 2 Mechanical properties and internal friction of heavily hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass (HMG) rods with a diameter of 1.5 mm. Included in the table are data for non-hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass for comparison. f , compressive fracture strength; HV, Vickers hardness; Qp−1 , peak interna1l friction; Tp , peak internal friction temperature. Metallic glass
f (GPa)
HV × 10−1
Qp−1 × 103
Tp (K)
HMG Zr55 Al10 Ni5 Cu30 rod Non-hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass rod
1.81 1.84
5.1 4.7
8.1 –
273 –
4. Conclusions
Fig. 5. Temperature dependence of the internal friction of HMG rods with diameters of 1.0 and 1.5 mm.
the Zr-based metallic glass has little effect on the fracture strength. From a practical standpoint, damping materials must be available in bulk form and have mechanical strength and internal friction higher than 1 GPa and 10 × 10−3 [27], respectively. The HMG prepared in this study, fulfill the above requirements. However, the peak temperature is too low (∼273 K) thus, this is the only remaining point to be overcome for using HMGs as damping materials.
This article describes the summary of our recent studies on two important topics concerned with recent researches on the damping of hydrogenated metallic glasses (HMGs), aimed at the clarification of the mechanism of the high hydrogen-induced internal friction of HMGs and at the materials processing of “bulk” HMGs for engineering. Concerning the first topic it has been found that the Zr atoms form a very similar fundamental structure in both metallic glasses. The Zr atoms are predominantly in environments which form icosahedron-like polyhedra, with a total coordination number in excess of 12. In addition, the Voronoi analysis of the Ni and Cu atoms shows a clear difference in the atomic configuration of these metallic glasses. The polyhedra around Ni atoms are dominated by trigonal prismatic-like, Archimedian antiprismatic-like, and similar polyhedra, with total coordination numbers less than 10. In contrast, icosahedron-like polyhedra are found to dominate in the environment around Cu atoms, with total coordination numbers in excess of 11. The Voronoi analysis has been also done in the same way to clarify the tetrahedron in these Zr66.7 Ni33.3 and Zr66.7 Cu33.3 metallic glasses. It is found that the fraction of the Zr-rich tetrahedron in the Zr66.7 Ni33.3 metallic glass is larger than that in the Zr66.7 Cu33.3 one. This accounts for the observed difference in the temperature dependence of their internal friction. The main conclusions concerning the second metal glass are described below. Zr-based bulky hydrogenated metallic glasses with Tx = ∼60 K were successfully prepared for the first time by a powder-compact-melting and liquid-casting process using Zr–Al–Ni–Cu metallic glass and ZrH powders as the starting materials. They show a broad internal friction peak at ∼273 K, whose height is ∼8 × 10−3 . Their compression fracture strength and Vickers hardness were about 1.8 GPa and 500, respectively. Since the practical level of the damping materials is 1 GPa for strength and 10 × 10−3 for internal friction, it can be concluded that the powdercompact-melting and liquid-casting process using metallic glass and metal hydride powders is suitable for the production of highdamping materials. Acknowledgements The author is grateful to K. Ito and T. Fukunaga, Kyoto University, and D. Nagata and T. Wada, Tohoku University, for their collaboration and useful discussion through this research. References
Fig. 6. Compressive stress–strain curves of hydrogenated and H-free HMG rods of 1.5 mm diameter at a strain rate of 5.0 × 10−4 s−1 .
[1] A. Inoue, Mater. Trans. JIM 36 (1995) 866. [2] W.L. Johnson, Mater. Sci. Forum 225–227 (1996) 35. [3] T. Yagi, R. Oguro, R. Tamura, S. Takeuchi, Mater. Res. Soc. Symp. Proc. (MRS2000), Mater. Res. Soc., 2001, p. L11.10.1. [4] T. Yagi, R. Tamura, S. Takeuchi, Proc. 4th Pacific Rim Intern. Conf. on Advanced Mater. Proc. (PRICM4) the Japan Inst. Metals, 2002, p. 139. [5] T. Yagi, T. Imai, R. Tamura, S. Takeuchi, Mater. Sci. Eng. 370 (2004) 264. [6] S. Takeuchi, T. Yagi, T. Imai, R. Tamura, Mater. Sci. Eng. A 375–377 (2004) 455. [7] H.R. Sinning, J. Alloys Compd. 310 (2000) 224. [8] R. Scarfone, H.R. Sinning, J. Alloys Compd. 310 (2000) 229. [9] H. Mizubayashi, S. Murayama, H. Tanimoto, J. Alloys Compd. 330–332 (2002) 389. [10] H. Mizubayashi, Y. Ishikawa, H. Tanimoto, Mater. Trans. 43 (2002) 2662.
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[11] H. Mizubayashi, Y. Ishikawa, H. Tanimoto, J. Alloys Compd. 355 (2003) 31. [12] H. Mizubayashi, Y. Ishikawa, H. Tanimoto, Mater. Sci. Eng. 370 (2004) 546. [13] M. Hasegawa, S. Yamaura, H. Kato, K. Amiya, N. Nishiyama, A. Inoue, J. Alloys Compd. 355 (2003) 37. [14] M. Hasegawa, K. Kotani, S. Yamaura, H. Kato, I. Kodama, A. Inoue, J. Alloys Compd. 365 (2004) 221. [15] M. Hasegawa, M. Takeuchi, H. Kato, S. Yamaura, A. Inoue, J. Alloys Compd. 372 (2004) 116. [16] M. Hasegawa, M. Takeuchi, H. Kato, A. Inoue, Acta Mater. 52 (2004) 1799. [17] M. Hasegawa, M. Takeuchi, A. Inoue, Acta Mater. 53 (2005) 5297. [18] M. Hasegawa, M. Takeuchi, H. Kato, S. Yamaura, A. Inoue, Mater. Sci. Eng. 442 (2006) 106.
[19] T. Fukunaga, K. Itoh, T. Otomo, K. Mori, M. Sugiyama, H. Kato, M. Hasegawa, A. Hirata, Y. Hirotsu, A.C. Hannon, Intermetallics 14 (2006) 893. [20] M. Hasegawa, K. Itoh, T. Fukunaga, submitted for publication. [21] M. Hasegawa, D. Nagata, A. Inoue, submitted for publication. [22] R.L. McGreevy, L. Pusztai, Mol. Simulat. 1 (1988) 359. [23] D. Suh, R.H. Dauskardt, Mater. Trans. 42 (2001) 638. [24] M. Hasegawa, D. Nagata, T. Wada, A. Inoue, Acta Mater. 54 (2006) 3221. [25] V.S. Stepanyuk, A. Szasz, A.A. Katsnelson, O.S. Trushin, H. Müller, H. Kirchmayr, J. Non-Cryst. Solids 159 (1993) 80. [26] A. Inoue, T. Zhang, Mater. Trans. 36 (1995) 1184. [27] K. Sugimoto, Mem. Inst. Sci. Ind. Res., Osaka University, Japan 35 (1978) 31.
Contents lists available at ScienceDirect
Materials Science and Engineering A journal homepage: www.elsevier.com/locate/msea
Hydrogen-induced high damping of bulk metallic glasses M. Hasegawa Department of Materials Science and Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan
a r t i c l e
i n f o
Article history: Received 30 June 2008 Accepted 8 October 2008 Keywords: Local structure Interstitial site Internal friction Hydrogen Metallic glass Compressive strength
a b s t r a c t There are two important topics concerned with the recent researches on the damping materials of hydrogenated metallic glasses (HMGs). One is the mechanism of the high hydrogen-induced internal friction of HMGs. The other is the materials processing of “bulk” HMGs for engineering. This article describes the summary of our recent studies on these topics. The first one is closely related to the local structure of the metallic glasses. Therefore, our recent results on the intermediate-range local structure of the simple two Zr-based metallic glasses are described, which has been clarified by the Voronoi analysis using the experimental data of the neutron diffraction measurements. The hydrogen-induced internal friction of HMGs is also discussed on the basis of these recent results of the local structure of the metallic glasses. In terms of the second topic, the first successful preparation of heavily hydrogenated Zr-based bulk HMG rods without hydrogen-induced surface embrittlement is described. They are prepared by a powdercompact-melting and liquid-casting process using Zr–Al–Ni–Cu metallic glass and ZrH2 powders as the starting materials. It has been found that they have high damping properties. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Metallic glasses can be prepared in bulk form and have high mechanical strength as well as high corrosion resistance [1,2]. Since these are key materials characteristics, metallic glasses may become more widely used. Most metallic glasses contain some alloying elements that have high affinity for hydrogen such as Zr, Ti, Hf, Mg and rare earth elements. Thus, metallic glasses can readily absorb hydrogen. Hydrogenated metallic glasses (HMGs) can be used as damping materials since they have high mechanical strength and exhibit high internal friction due to re-ordering of the hydrogen. Although there have been many reports on the hydrogen-induced internal friction of HMGs [3–18], there are still two important aspects that need to be investigated. One is the mechanism of the high hydrogen-induced internal friction of HMGs. The other is the processing of “bulk” HMGs to be used as engineering high damping materials. This article describes the summary of our recent studies on these two aspects [19–21]. The first aspect is closely related to the local structure of the bulk metallic glasses because the hydrogen atoms, which induce internal friction, occupy interstitial sites in the local structure of the metallic glasses. Accordingly, it is important to clarify the energy distribution of the interstitial sites for hydrogen in the glassy structure to discuss the hydrogen-induced internal friction. We have recently clarified the intermediate-range local structure of the two
E-mail address: [email protected]. 0921-5093/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2008.10.078
simple Zr66.7 Ni33.3 and Zr66.7 Cu33.3 metallic glasses by the Voronoi analysis using experimental data of neutron diffraction measurements [19]. An analysis of Voronoi polyhedra in the Reverse Monte Carlo (RMC) simulations based on the diffraction data makes it possible to characterize the atomic configurations around the constituent atoms. The RMC modeling [23] has been recognized to be an excellent method for visualizing the three-dimensional atomic arrangement of liquid and amorphous materials, based on the results of diffraction experiments. In this article the hydrogeninduced internal friction of HMGs will be discussed briefly on the basis of these recent results of the intermediate-range local structure of the metallic glasses. The other recent important aspect is the materials processing of “bulk” HMGs for engineering. The electrochemical technique is currently the most popular method of hydrogenating metallic glasses. There are many reports on the hydrogen-induced internal friction of metallic glasses hydrogenated by this technique [3–18]. However, they only report the results on hydrogenated metallic glass “ribbon” samples with a thickness of ∼20 m. When one tries to introduce a high amount of hydrogen into the bulk metallic glass by the electrochemical technique, the sample usually deforms and its surface peels off [23]. This is why the ribbon samples were used to investigate hydrogen-induced internal friction in the labbased studies. However, it is extremely important to prepare and study “bulky” hydrogenated metallic glasses in order to use them as engineering high-damping materials. We were the first to successfully investigate the temperature dependence of hydrogen-induced internal friction of “bulky” hydrogenated Zr-based metallic glasses in the form of rods of 1.5 mm diameter [13,14]. However, the hydro-
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gen content of the rod was only about 2 at.%. Recently, we have succeeded in preparing heavily hydrogenated Zr-based bulk metallic glasses for the first time by a powder-compact-melting and liquid-casting process. We used Zr–Al–Ni–Cu metallic glass and ZrH powders as the starting materials which had earlier been developed by us to prepare Zr-based glassy composite alloys containing dispersed crystalline ZrN [24]. In this article, the results of the hydrogen-induced internal friction and mechanical properties of heavily hydrogenated Zr–Al–Ni–Cu bulk metallic glass will be reported. 2. Interstitial site for hydrogen in metallic glass Metallic glass ribbons were synthesized by rapid quenching from the molten state using a single roller technique under Ar gas atmosphere. The neutron diffraction experiment was carried out using the High Intensity Total scattering spectrometer HIT-II at the High Energy Accelerator Research Organization (KEK), Tsukuba, Japan. Time-of-flight neutron diffraction using a spallation neutron source makes it possible to measure S(Q) over a wide Q range (from QZ5 nmK1 up to 200 nmK1 in this case), leading to a high resolution in real-space. The Reverse Monte Carlo (RMC) modeling [22] is a simple variant of the standard Monte Carlo procedure, which provides a powerful method for deriving three-dimensional simulations of the atomic arrangements of disordered materials. The local atomic environment for the simulations was characterized by means of a Voronoi analysis [25]. The distribution of the Voronoi polyhedra is expressed in terms of Schlafli notation where a polyhedron is denoted by a set of indices n3, n4, n5, n6, n7, n8, where ni is the number of faces with i vertices. The details of the experimental procedure and data analysis were described elsewhere [19]. The polyhedral environment in the RMC simulations of the Zr66.7 Ni33.3 and Zr66.7 Cu33.3 metallic glasses was investigated by means of a Voronoi analysis, in which the Voronoi polyhedra around Ni, Cu and Zr atoms were analyzed independently [19]. Although the detailed results of the analyses are not described in this article, what should be pointed out here again is that the Voronoi polyhedron analysis is powerful to understand the distribution fraction of the polyhedron in the structure of the metallic glass. Therefore, we have also applied the Voronoi analysis to clarify the tetrahedron in these Zr66.7 Ni33.3 and Zr66.7 Cu33.3 metallic glasses [20] because the polyhedrons concerned with the hydrogen-induced internal friction of Zr-based HMGs are tetrahedrons containing Zr which has a high affinity for hydrogen, i.e. 4Zr, 3Zr + 1 M, 2Zr + 2 M and 1Zr + 3 M (M = Ni or Cu). Fig. 1 shows the fraction of the 4Zr, 3Zr + 1 M, 2Zr + 2 M and 1Zr + 3 M tetrahedrons. It is found that the fraction of the Zr-rich tetrahedrons in the Zr66.7 Ni33.3 metallic glass is larger than that in the Zr66.7 Cu33.3 one. This means that the interstitial site distribution for hydrogen as a function of site energy is different from each other. Since the interstitial site distribution for hydrogen is directly related to the re-ordering of hydrogen atoms, which leads to the hydrogen-induced internal friction, it is expected that the temperature dependence of the internal friction is also different from each other. Therefore, it is extremely interesting to measure the temperature dependence of the hydrogen-induced internal friction of these Zr66.7 Ni33.3 and Zr66.7 Cu33.3 metallic glasses and to compare the results with data in Fig. 1. 3. Bulk hydrogenated metallic glass Alloy ingots of Zr53 Al11 Ni5 Cu31 were prepared in an arc-melting furnace in a purified argon atmosphere. The metallic glass powder was prepared by a conventional spray method in a purified argon atmosphere. Rod samples were prepared by a conventional copper-mold cast method in a purified argon atmosphere using
Fig. 1. Fraction of the 4Zr, 3Zr + 1 M, 2Zr + 2 M and 1Zr + 3 M (M = Ni or Cu) tetrahedrons of the Zr66.7 Ni33.3 (closed) and Zr66.7 Cu33.3 (open) metallic glasses.
a compacted mixture of the metallic glass and ZrH powders. The mass fraction of the starting ZrH powder was 4.8 mass%, with an expected final composition of (Zr55 Al10 Ni5 Cu30 )-H. The morphology of the sample and its surface were examined using a SEM. Chemical composition was analyzed using an SEM-EDX. Phases of the sample were identified by an X-ray diffraction method using monochromatized Cu-K␣ radiation. Thermal stability was investigated by DSC in a flowing purified argon atmosphere. The heating rate during the measurement was about 0.67 K/s. The hydrogen content of the samples was determined using an inert gas carrier melting thermal conductivity method. The internal friction measurements were carried out using a reed method over the temperature range of ∼90 to ∼380 K while under vacuum (∼10−2 Pa). The internal friction was measured using a resonance oscillation method at a frequency of ∼600 Hz. The strain amplitude was ∼1.0 × 10−5 . Details of the instrumental setup and measurement procedures have been described elsewhere [14]. Mechanical properties were estimated by measuring tensile or compression strength using an Instron testing machine and Vickers hardness. Straight cylindrical rods with a diameter of 1.0 and 1.5 mm and a length of about 50 mm were obtained. The hydrogen content of each rod was determined to be 7.0 and 7.3 at.%, respectively. This is about three times higher than the earlier reported hydrogen content of the Zr-based bulk metallic glass rod introduced by the electrochemical technique [13,14]. The analyzed composition of the alloy was Zr55 Al10 Ni5 Cu30 , as expected. SEM images of HMG rods reveal a smooth and shiny surface (Fig. 2). Fig. 2(b) shows SEM images of the surface of an HMG rod with a diameter of 1.5 mm. It should be noted that there are no cracks on the surface. Therefore, their morphology is the same as that of non-hydrogenated metallic glass and is completely different from that of rods hydrogenated by the electrochemical technique. Fig. 3 shows a cross-section of the X-ray diffraction pattern of rods with a diameter of 1.0 and 1.5 mm. The pattern was composed of only halo patterns, indicating that the prepared rod alloys were composed only of the amorphous phase. Fig. 4 shows DSC curves of the HMG rods with diameters of 1.0 and 1.5 mm; they show a small endothermic peak preceding a large exothermic peak, corresponding to a supercooled liquid and crystallization region, respectively. This indicates that the prepared amorphous rods are glassy. The
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Fig. 4. DSC curves of HMG rods with diameters of 1.0 and 1.5 mm.
Fig. 2. SEM images of hydrogenated Zr55 Al10 Ni5 Cu30 glass alloy rod with a diameter of 1.5 mm prepared by a powder-compact-melting and liquid-casting process using Zr–Al–Ni–Cu metallic glass and ZrH powders as the starting materials: (a) rod sample and (b) surface.
glass transition and crystallization temperatures, Tg and Tx , and the supercooled liquid region (Tx = Tx − Tg ) are summarized in Table 1. Data of the non-hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass are also listed for comparison [26]. The values for HMG rods with diameters of 1.0 and 1.5 mm are almost the same. This finding is consistent with the results of their hydrogen content analysis above. It should be noted that these values are different from those of the non-hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass rod even though their analyzed compositions are the same. This is attributable to interstitial hydrogen in the Zr–Al–Ni–Cu metallic glass. That is to say, the interstitial hydrogen decreases the glass forming ability by decreasing Tx . Fig. 5 shows the temperature dependence of the internal friction of HMG rods with a diameter of 1.0 and 1.5 mm. Both HMG rods show a broad internal friction peak at ∼273 K with peak values of ∼8 × 10−3 . It should be noted that their peak values are almost the same. This is consistent with their nearly identical hydrogen contents. Yagi et al. reported that the hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass ribbon absorbing about 6 at.%H showed an internal friction peak of ∼7 × 10−3 at ∼273 K [4]. The results of the present study are consistent with this report. Therefore, it is concluded that heavily and homogeneously hydrogenated Zr-based bulky metallic glass rods can be prepared by the powder-compact-melting and liquid-casting process as in this study. Fig. 6 shows the compressive stress–strain curve of the hydrogen loaded and hydrogen free Zr55 Al10 Ni5 Cu30 metallic glass rod of 1.5 mm diameter. Their mechanical properties and internal friction are summarized in Table 2. The compression fracture strength of the HMG rod was about 1.8 GPa, almost the same as that of the H free material. This indicates that interstitial hydrogen (∼7 at.%H) in Table 1 Thermal stability parameters of hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass prepared by a powder-compact-melting and liquid-casting process. Included in the table are data for non-hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass. Tg , glass transition temperature; Tx , crystallization temperatures, Tx = Tx − Tg , supercooling region.
Fig. 3. X-ray diffraction pattern of a cross-section of HMG rods with diameters of 1.0 and 1.5 mm.
Metallic glass
Tg (K)
Tx (K)
Tx (K)
HMG rod (1.0 mm diameter) HMG rod (1.5 mm diameter) Non-hydrogenated metallic glass rod
697 697 683
755 757 767
58 60 84
This study This study Ref. [26]
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Table 2 Mechanical properties and internal friction of heavily hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass (HMG) rods with a diameter of 1.5 mm. Included in the table are data for non-hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass for comparison. f , compressive fracture strength; HV, Vickers hardness; Qp−1 , peak interna1l friction; Tp , peak internal friction temperature. Metallic glass
f (GPa)
HV × 10−1
Qp−1 × 103
Tp (K)
HMG Zr55 Al10 Ni5 Cu30 rod Non-hydrogenated Zr55 Al10 Ni5 Cu30 metallic glass rod
1.81 1.84
5.1 4.7
8.1 –
273 –
4. Conclusions
Fig. 5. Temperature dependence of the internal friction of HMG rods with diameters of 1.0 and 1.5 mm.
the Zr-based metallic glass has little effect on the fracture strength. From a practical standpoint, damping materials must be available in bulk form and have mechanical strength and internal friction higher than 1 GPa and 10 × 10−3 [27], respectively. The HMG prepared in this study, fulfill the above requirements. However, the peak temperature is too low (∼273 K) thus, this is the only remaining point to be overcome for using HMGs as damping materials.
This article describes the summary of our recent studies on two important topics concerned with recent researches on the damping of hydrogenated metallic glasses (HMGs), aimed at the clarification of the mechanism of the high hydrogen-induced internal friction of HMGs and at the materials processing of “bulk” HMGs for engineering. Concerning the first topic it has been found that the Zr atoms form a very similar fundamental structure in both metallic glasses. The Zr atoms are predominantly in environments which form icosahedron-like polyhedra, with a total coordination number in excess of 12. In addition, the Voronoi analysis of the Ni and Cu atoms shows a clear difference in the atomic configuration of these metallic glasses. The polyhedra around Ni atoms are dominated by trigonal prismatic-like, Archimedian antiprismatic-like, and similar polyhedra, with total coordination numbers less than 10. In contrast, icosahedron-like polyhedra are found to dominate in the environment around Cu atoms, with total coordination numbers in excess of 11. The Voronoi analysis has been also done in the same way to clarify the tetrahedron in these Zr66.7 Ni33.3 and Zr66.7 Cu33.3 metallic glasses. It is found that the fraction of the Zr-rich tetrahedron in the Zr66.7 Ni33.3 metallic glass is larger than that in the Zr66.7 Cu33.3 one. This accounts for the observed difference in the temperature dependence of their internal friction. The main conclusions concerning the second metal glass are described below. Zr-based bulky hydrogenated metallic glasses with Tx = ∼60 K were successfully prepared for the first time by a powder-compact-melting and liquid-casting process using Zr–Al–Ni–Cu metallic glass and ZrH powders as the starting materials. They show a broad internal friction peak at ∼273 K, whose height is ∼8 × 10−3 . Their compression fracture strength and Vickers hardness were about 1.8 GPa and 500, respectively. Since the practical level of the damping materials is 1 GPa for strength and 10 × 10−3 for internal friction, it can be concluded that the powdercompact-melting and liquid-casting process using metallic glass and metal hydride powders is suitable for the production of highdamping materials. Acknowledgements The author is grateful to K. Ito and T. Fukunaga, Kyoto University, and D. Nagata and T. Wada, Tohoku University, for their collaboration and useful discussion through this research. References
Fig. 6. Compressive stress–strain curves of hydrogenated and H-free HMG rods of 1.5 mm diameter at a strain rate of 5.0 × 10−4 s−1 .
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