Temperature dependence of micro-deformation behavior of the porous tungsten/Zr-based metallic glass composite

https://doi.org/10.1016/j.jnoncrysol.2016.01.005Get rights and content

Highlights

  • The mechanical properties of the porous tungsten/Zr-based metallic glass composite during cyclic compression at different temperatures were investigated.

  • An in-situ high energy X-ray diffraction and a finite element modeling were used to investigate the micro-deformation behavior of the composite.

  • Both the temperature and the pre-deformation from the cyclic loading have great influence on the work hardening behavior of the tungsten phase.

Abstract

The effect of temperature on the micro-deformation behavior of the porous tungsten/Zr-based metallic glass composite was investigated during cyclic compression by synchrotron based in-situ high-energy X-ray diffraction (HEXRD) and finite element modeling (FEM). Both the metallic glass phase and the tungsten phase remained elastic in the first loading at different temperatures. The metallic glass phase also exhibits “work hardening” behavior, which is attributed to the crystallization of the metallic glass phase during deformation at high temperature. The yield strength of the tungsten phase during the second loading decreased with the increase of temperature while remained almost equal in the third loading. Both the temperature and the pre-deformation from the cyclic loading have great influence on the work hardening behavior of the tungsten phase. The influence of the pre-deformation after the second cyclic loading is greater than the influence of the temperature during the third loading.

Introduction

Bulk metallic glasses (BMGs) have many superior mechanical properties [1], [2], [3]. However, the fracture of BMGs is highly localized by shear bands during deformation, leading to nearly no macroscopic plasticity [4], [5], [6]. In order to improve the plasticity of BMGs, considerable efforts were taken to develop BMG based composites (BMGCs) [7], [8], [9], [10]. The reinforcements of BMGCs could obstruct the rapid propagation of one major shear band and induce the formation of multiple shear bands, which are demonstrated to be responsible for enhancing the plasticity of BMGCs. The porous tungsten reinforced BMGCs exhibited work hardening behavior and excellent plasticity, which is attributed to that the porous tungsten phase could hinder the propagation of shear bands in three-dimensional (3D) directions [11], [12].

Temperature has great influence on the mechanical properties of materials whose structure is unstable with the change of temperature, especially for BMGs. Up to now, tremendous efforts have been devoted to investigate the deformation mechanisms of BMGs [13], [14], [15], [16], [17], [18], [19], [20], certainly including the influence of temperature on the mechanical properties of BMGs [21], [22], [23], [24], [25], [26], [27], [28], [29]. However, limited literature is available on the effect of temperature on BMGCs. Qiao et al. reported that the Ti-based BMGC exhibited a decreased yield strength while an increased toughness with the increase of temperature [30]. Roberts et al. reported that both the Zr-based and the Ti-based BMGCs exhibited an increased yield strength but a steep decrease in toughness as the temperature decreased from the ambient temperature [31]. The present work is helpful for understanding the effect of temperature on the deformation mechanisms of the present composite, which is the key for the composite to be used in high-temperature environment. On the other hand, in order to improve the mechanical properties of BMGs, except for optimizing the composition of alloys and developing composites with different reinforced modes, deformation processing could also be available, for example, cold rolling, swaging, and hydrostatic extrusion [32], [33], [34]. Thus, the present work could also be helpful for the hot work of the present composite.

In the present study, to interpret the effect of temperature on the mechanical properties of the porous tungsten/Zr-based metallic glass composite during cyclic compression, a high energy X-ray diffraction (HEXRD) and finite element modeling (FEM) were used to investigate the micro-deformation behavior of the composite. The stress distribution and the load transferring behavior between the two phases during deformation at different temperatures were discussed in detail.

Section snippets

Experimental

The ingots of Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 alloy were prepared by arc-melting a mixture of the five elements (the purity of the elements is above 99.5%) in a Ti-gettered argon atmosphere. The porous tungsten with volume fraction of 80% was prepared by powder metallurgy in a hydrogen atmosphere. The details of casting could be found elsewhere [12].

An in-situ synchrotron-based HEXRD technique was employed to study the micro-deformation behavior of the composite at different temperatures. The

Macro-mechanical behavior of the composite

Fig. 2 shows the stress–strain curves of the composite at different temperatures during cyclic compression. In the first loading–unloading cycle, the composite essentially experiences only elastic deformation at all the testing temperatures. In the second cycle, the composite shows elastic-to-plastic deformation regime at all the testing temperatures, and the yield stress decreases with the increase of temperature. In the third cycle, the yield strength shows obviously lower at the low

Mechanical behavior of the tungsten phase

Fig. 9 shows the yield stress and work hardening exponent n of the tungsten phase with the testing temperatures during the second and the third loading. As seen in Fig. 9, the tungsten phase exhibits a decreased yield stress with the increase of temperature in the second loading, while the tungsten phase exhibits almost equal yield stress except that at 213 K during the third loading. The yield strength of the metallic glass phase decreased sharply when the testing temperature near Tg [26].

Conclusion

The micro-deformation behavior of the porous tungsten/Zr-based metallic glass composite was investigated under cyclic compression at different temperatures by synchrotron based in-situ high-energy X-ray diffraction (HEXRD) and finite element modeling (FEM). The main results are listed as follows:

(1) Both the tungsten phase and the metallic glass phase remained elastic during the first loading at all the testing temperatures. The tungsten phase exhibits decreased yield strength with the increase

Acknowledgments

This work is supported by National Natural Science Foundation of China (Grant Nos. 51471035, 51101018, and 51271036), Hundred Talents Program of the Chinese Academy of Sciences, and Beijing Higher Education Young Elite Teacher Project. The use of the Advanced Photon Source was supported by the US Department of Energy, Office of Science Laboratory.

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