Significant plasticity enhancement of ZrCu-based bulk metallic glass composite dispersed by in situ and ex situ Ta particles

doi:10.1016/j.msea.2012.05.013

Materials Science and Engineering: A

Volume 551, 15 August 2012, Pages 249-254

https://doi.org/10.1016/j.msea.2012.05.013 Get rights and content

Abstract

Using two-step arc melting process and suction casting, the Zr_47.3Cu₃₂Al₈Ag₈Ta₄Si_0.7-based bulk metallic glass composites (BMGCs) rods with ex situ added micro-sized Ta particles have been successfully fabricated. The structure and thermal properties of these BMGCs samples were examined by differential scanning calorimeter (DSC) and X-ray diffraction (XRD). It was found that these BMGCs with ex situ added Ta exhibit similar thermal properties in comparison with their base alloy counterpart, with relatively high glass forming ability (GFA). For the mechanical study, the results of compression test show that more than 25% compressive plastic strain and 1800 MPa fracture strength at room temperature can be obtained for the 2 mm diameter rod of the ZrCu-based BMGC ex situ added 6 and 9 vol.% Ta particles, respectively. Images from SEM on the fractured surfaces show that the homogeneously distributed Ta particles (20 ± 8 μm) would form semi-uniform confinement zones to restrict the shear band propagation. In other words, the inter-particle free space and the size of confinement zone (mean free path of shear bands) is apparently the controlling factor in affecting the plasticity of BMGCs.

Graphical abstract

Confinement zone of Ta particles provide a plastic shielding to obstruct shear banding and so as to significantly increase the plasticity of Zr-based BMGC. Evidence of remarkable plasticity improvement of Zr-based BMGC dispersed by the combination of in situ and ex situ Ta particles can be seen from the stress–strain curve (a) as well as the fractured samples of monolithic BMG ((b): brittle fracture) and BMGC ((c): severe plastic deformation).

Highlights

► Shear bands are arrested by the interface of glassy matrix/Ta in the Zr-based BMGCs. ► Ta particles of BMGC distributed as a semi-uniform confinement zone. ► Confinement zone exhibits smaller size than plastic zone of crack-tip in the BMGC. ► Confinement zone of Ta provide a plastic shielding to obstruct shear banding. ► Plasticity can be improved from 0% (monolithic BMG) to 44% plastic strain (BMGC).

Introduction

Among the recently developed bulk metallic glasses (BMGs), Zr-based BMG has been considered to be one of the most promising materials and has attracted much attention due to its exceptional properties, such as a high strength, high hardness, high elastic strain up to 2%, good wear resistance, and near perfect as-cast surfaces, exceptional glass-forming ability (GFA) and an extremely wide supercooled liquid region (ΔT_x is above 50 K, ΔT_x is defined as the difference between the glass transition temperature T_g and the onset crystallization temperature T_x) [1], [2], [3], [4], [5], [6], [7], [8]. However, almost all monolithic Zr-based BMGs fail catastrophically without obvious macroscopic plasticity due to the formation of highly localized shear bands [1], [5], [6], [7], [8], [9]. In order to improve the plasticity of monolithic Zr-based amorphous alloy, both micro- or nano-scaled chemical inhomogeneities [10], [11], [12], [13], [14], [15], [16], [17], [18], [19] and the bulk metallic glass composites (BMGCs) [20], [21], [22], [23], [24], [25], [26], [27], [28], [29] have been developed.

Apart from forming phase-separated amorphous phases, two main approaches of synthesizing BMGCs have been developed so far, one is to in situ precipitate crystalline phases in the BMG matrix, the other is to ex situ introduce foreign particles or micrometer-sized pores into the BMG matrix. Though the ex situ composites can be synthesized from any bulk amorphous alloy composition, they have problems of a limited size of dispersoids and the bonding strength at interface between the dispersoids and the matrix. On the contrary, the in situ composites contain finer crystalline precipitates by simply adjusting the alloy composition or cooling rate. However, some added elements may form the intrinsically brittle intermetallic compounds, which often reduces the ductility of materials [30]. Only a few refractory metals, such as Nb and Ta can form ductile crystalline phases (such as Nb-rich or Ta-rich solid solution phase) in the Zr-based BMGs according to their binary phase diagram [31]. However, these in situ BMGCs have limited compositions and are very sensitive to their fabrication process, such as cooling rate.

In our previous report, it was found that the size distribution of in situ Ta-rich precipitate randomly varies from 20 nm to 30 μm with the increasing Ta content [29]. This reveals an opportunity to fabricate new BMGCs by combining in situ and ex situ to create more volume fraction of micro-size Ta particles with a controllable and uniform distribution. Therefore based on our previous results, we choose Zr_47.3Cu₃₂Al₈Ag₈Ta₄Si_0.7 as the matrix to form a new composite with ex situ added micro-sized Ta particles (about 20 μm). Zr_47.3Cu₃₂Al₈Ag₈Ta₄Si_0.7 was selected for its substantial plasticity (∼5%) due to in situ micro-sized Ta-rich precipitates [29]. The microstructures and mechanical behaviors of this new ZrCu-based BMGC will be investigated in detail.

Section snippets

Experimental details

The alloy ingots with different compositions of Zr_47.3Cu₃₆Ag₈Al₈Si_0.7 and Zr_47.3Cu₃₂Ag₈Al₈Ta₄Si_0.7 were prepared by arc melting the appropriate mixture of high purity Zr, Cu, Al, Ag, Si, and Ta under a Ti-gettered argon atmosphere, respectively. In order to make the composition homogeneous, a two-step melting process was carried out; at first, raw metals of Zr and Ta, which have the highest melting temperatures in this alloy system were melted together to form a homogeneous solid solution

Thermal properties of the as-cast ZrCu-based BMGC

The DSC scans on the Zr_47.3Cu₃₂Ag₈Al₈Ta₄Si_0.7 rods with 0, 3, 6 and 9 vol.% ex situ added Ta particles are shown in Fig. 1. All samples exhibit a clear glass transition followed by a region of supercooled liquid phase before crystallization. Values of glass transition (T_g), crystallization (T_x), and supercooled liquid range (ΔT_x), GFA indicators γ = T_g/(T_g + T_l) [32] and γ_m = (2T_x − T_g)/T_l [33] are listed in Table 1. Variations of T_g, T_x and ΔT_x of sample rods with ex situ added Ta are not significantly

Conclusion

In summary, the Zr_47.3Cu₃₂Al₈Ag₈Ta₄Si_0.7-based BMGCs ex situ dispersed 3–9 vol.% micro-sized Ta particles have been successfully fabricated in this study. It was found that shear bands are arrested at the amorphous matrix–Ta interfaces in these ZrCu-based BMGCs. The traveling distance, i.e. mean free path, of shear bands is limited by the mean inter-particle spacings of Ta particles. For a given size of Ta particles, the higher volume fraction of particles would lead to shorter inter-particle

Acknowledgments

The authors would like to gratefully acknowledge the sponsorship from the National Science Council of ROC under the project NSC98-2221-E-008-116-MY3 and NSC99-3113-P-008-003 and NSC100-2120-M-110-004. In addition, the authors also like to acknowledge the help on TEM analysis by the Micro and Nano Analysis Laboratory of I-Shou University.

References (37)

A. Inoue
Acta Mater.
(2000)
W.H. Wang et al.
Mater. Sci. Eng. R
(2004)
A. Inoue et al.
Acta Mater.
(2011)
C.A. Schuh et al.
Acta Mater.
(2007)
H.A. Bruck et al.
Scripta Metall. Mater.
(1994)
M.H. Lee et al.
Intermetallics
(2004)
J.C. Oh et al.
Scripta Mater.
(2005)
E.S. Park et al.
Acta Mater.
(2006)
J. Eckert et al.
Intermetallics
(2002)
T. Zhang et al.
J. Alloys Compd.
(2007)

X.H. Du et al.

Intermetallics

(2009)

J. Pan et al.

Scripta Mater.

(2009)

J.S.C. Jang et al.

J. Alloys Compd.

(2011)

L. Liu et al.

Mater. Sci. Eng. A

(2007)

Z. Zhu et al.

Scripta Mater.

(2010)

J.S.C. Jang et al.

Intermetallics

(2010)

G. He et al.

Acta Mater.

(2003)

Z.P. Lu et al.

Intermetallics

(2004)

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Citation Excerpt :
In general, the deformation of BMGs at room temperature is carried out by shear banding, and the highly localization of shear banding leads to the brittle fracture with limited plasticity and vein-like patterns on the fracture surface, as displayed in Fig. 7a. By introducing a second phase in the amorphous matrix, such as Ta particles, the rapid propagation of main shear band could be inhibited, and multiple shear bands will be promoted, giving rise to the improved deformability (Fig. 7b) [9,10,25,28–32]. On the whole, shear banding still governs the deformation and fracture process of un-notched BMGs and BMGCs, as evidenced by the vein-like patterns on the fracture surface [25,28,33,34]. However, shear banding can be effectively suppressed in the notched BMGs and BMGCs under the triaxial stress state [35], and cavitation transits to the dominant deformation process at the initial stage of failure [15,20].
The existence of second phase usually promotes the formation of multiple shear bands under uniaxial loading, leading to the apparent strain hardening and enhanced plasticity in bulk metallic glasses (BMGs). However, the effect of second phase on the fracture behavior of BMGs has been rarely investigated when shear banding is suppressed. In this work, the effect of Ta particles on the fracture behavior of notched bulk metallic glass composites (BMGCs) was investigated, where shear banding is suppressed due to the introduction of high triaxial stress state. With an increase in the volume fraction of Ta particles from 0 to 3.3%, the fracture strength significantly decreases from 2.70 to 1.20 GPa. Different from the vein-like patterns caused by shear banding, the fracture surface of notched BMGCs displays numerous equiaxed dimples and micro-cracks, indicating that voids nucleation and coalescence govern the fracture process. Due to the relatively weak bonding of the interface and the mechanical incompatibility between Ta particles and amorphous matrix, voids tend to nucleate at the interface during tensile deformation, giving rise to a reduction in the fracture strength of BMGCs.
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The ZrCu-B2 phase can effectively increase the plasticity for some specified Zr based metallic glasses composite (BMGC) by transformation induced plasticity (TRIP) mechanism. However, large and non-uniformly distributed ZrCu-B2 phases usually precipitate in the Zr-based BMGC samples by conventional copper mold casting. Therefore, the concept of inoculation in conventional solidification process was applied to modify the size and distribution of ZrCu-B2 phase in this study. Ta particles (size of 5–30 μm) with 0–4.0 vol% were added into the Zr48Cu47·5Al4Co0.5 BMG matrix as the inoculant. Ta particles can act as nucleation seeds for precipitating a homogeneously distributed ZrCu-B2 phase in the matrix. Moreover, the ZrCu-B2 precipitate size can be further controlled by different solidification cooling rates. It is clearly to see that the ZrCu-B2 phase embedded in the amorphous matrix for the Zr48Cu47·5Al4Co0.5 cast rods added with 0–0.75 vol% Ta particle cast by a copper mold at −30 °C (243 K, or a cooling rate of 650 K/s). In addition, the ZrCu-B2 phase exhibits a round shape and relatively homogeneous distribution. The optimum processes BMGC can exhibit significantly improved mechanical properties (1890 MPa fracture stress and 14% plastic strain) in comparison with the base BMGC (1560 MPa fracture strength and 7.5% plastic strain).
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Significant plasticity enhancement of ZrCu-based bulk metallic glass composite dispersed by in situ and ex situ Ta particles

Abstract

Graphical abstract

Highlights

Introduction

Section snippets

Experimental details

Thermal properties of the as-cast ZrCu-based BMGC

Conclusion

Acknowledgments

Acta Mater.

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Acta Mater.

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J. Alloys Compd.

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J. Alloys Compd.

Mater. Sci. Eng. A

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