Indentation size effect in bulk metallic glass

Jang, Jae-il; Yoo, Byung Gil; Kim, Yong Jae; Oh, Jun Hak; Choi, In Chul; Bei, Hongbin

doi:10.1016/j.scriptamat.2010.12.036

Cited by 80 publications

(27 citation statements)

References 36 publications

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“…This indicates that the Oliver and Pharr method [21], which was derived from purely elastic solution, may not be reasonable for the hardness calculation in the present case. Moreover, it is addressed that the Meyer's hardness method can correct the minor error due to the pile-up effect [6,19]. Therefore, Meyer's hardness that is defined as H = P max /A t is adopted.…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%

“…, where a is the averaged length measured from the center of the triangular impression to the corner with the aid of SEM [19] (see Fig. S1 in Supplementary material).…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%

“…During the indentation, the STZ and the free volume could prompt each other with a positive feedback [8]. As the activation of STZs and the creation of free volume always lead to a strain softening effect on the indentation hardness [10,19], the combination of more activated STZs and higher free volume creation gives rise to a larger strain softening. This corresponds to the parabolic reduction of the indentation hardness with the increasing peak-load (or indentation depth) presented in Fig.…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%

“…In addition, Bhattacharyya et al [6] demonstrated a lower strain rate sensitivity of the hardness under a higher peak-load, but the results of Ma et al [17,18] showed a much more positive rate sensitivity when the peak-load increased by 1 order of magnitude. Moreover, Jang et al [19] reported a continuous reduction of hardness with increasing peak-load or indentation size, i.e., an indentation size effect (ISE). On the contrary, Wang et al [20] recently demonstrated that the ISE would disappear when the indentation size is larger than a critical value.…”

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Testing effects on hardness of a Zr-based metallic glass under nanoindentation

Jiang

et al. 2017

Scripta Materialia

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A series of nanoindentation tests were performed on a Zr-based bulk metallic glass at different peak-loads and strain rates. It is observed that the strain rate sensitivity index gradually decreases from positive to almost zero with increasing peak-load. Furthermore, at a fixed strain rate, the indentation hardness firstly shows a dramatic reduction and then becomes stable with increasing peak-load. These observations can be well understood in the framework of the activation and the accumulation of free volume via shear transformation zones. The current work may provide a practical way to tailor the hardness of the metallic glass.© 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords:Metallic glass Nanoindentation Strain rate Indentation size effect Metallic glasses have been long regarded as potential structural materials due to their ultra-high strength and hardness [1,2]. Therefore, a number of researchers have paid much attention to the factors that will influence the hardness of metallic glass [3][4][5]. For instance, it is demonstrated that the increase of loading rate corresponded to a decrease of hardness and the underlying mechanism was attributed to the free volume relaxation induced hardening that was more dramatic under lower strain rates [6]. However, the free volume dynamics includes not only the relaxation induced annihilation, but also stress driven creation [7][8][9]. It is believed that the free volume creation could lead to a softening effect on the hardness of metallic glasses [10,11]. Therefore, both hardening and softening effects of strain rates on the hardness is possible. For example, Xue et al. [12] reported a positive strain rate dependence of the hardness and ascribed this correlation to the stronger strain rate softening effect under lower strain rates. There are also analogous inconsistent results, but the underlying mechanism has been rarely shed light on [13][14][15][16][17]. In addition, Bhattacharyya et al. [6] demonstrated a lower strain rate sensitivity of the hardness under a higher peak-load, but the results of Ma et al. [17,18] showed a much more positive rate sensitivity when the peak-load increased by 1 order of magnitude. Moreover, Jang et al. [19] reported a continuous reduction of hardness with increasing peak-load or indentation size, i.e., an indentation size effect (ISE). On the contrary, Wang et al. [20] recently demonstrated that the ISE would disappear when the indentation size is larger than a critical value.Evidently, the dependence of hardness on the testing conditions (strain rate and peak-load) under nanoindentation is still under debate. Further exploration is required to gain more insights into these issues. In the current work, a series of nanoindentation tests were performed on a Zr-based metallic glass under different peak-loads and strain rates. A positive dependence of hardness on the strain rate is found. Meanwhile, both the strain rate sensitivity index and the indentation hardness firstly decrease and then become stabl...

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Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%

“…, where a is the averaged length measured from the center of the triangular impression to the corner with the aid of SEM [19] (see Fig. S1 in Supplementary material).…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%

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confidence: 99%

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Testing effects on hardness of a Zr-based metallic glass under nanoindentation

Jiang

et al. 2017

Scripta Materialia

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“…3(a) has been widely reported in Zr, [34][35][36] Au, 37 and Fe-based BMGs, 38 while the detailed mechanisms are still far from complete understanding. Jang et al 36 suggested that the excess free volume induced by nanoindentation with small h final was not enough to trigger amounts of STZs in comparison to that with large h final , thus just a small amount of shear bands nucleated accompanied by higher hardness during nanoindentation with small h final . However, in the present work, the less the h was, the more serrations were induced (Fig.…”

Section: Indentation Size Effect (Ise)mentioning

confidence: 99%

Nanoindentation response of laser shock peened Ti-based bulk metallic glass

Wang

Xue

et al. 2015

AIP Advances

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The effect of laser shock peening (LSP) on mechanical properties of Ti-based bulk metallic glass (BMG) was investigated under nanoindentation. Two regions were generated within the specimen after the LSP: (I) the extremely thick softened region (∼300 µm) in which amounts of shear bands and excess free volume were generated; (II) the middle region where the free volume increased but nearly no shear bands were induced. The hardness decreased with the increase of the indenter depth (h), exhibiting indentation size effect (ISE). The ISE increased with the increase of the measured distance away from the laser shocked tip, indicating that the ISE was inhibited by the shear bands and excess free volume was generated by the LSP.

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Nanoindentation in Metallic Glasses

Nekouie

Roy

2017

Applied Nanoindentation in Advanced Materials

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Indentation size effect in bulk metallic glass

Cited by 80 publications

References 36 publications

Testing effects on hardness of a Zr-based metallic glass under nanoindentation

Testing effects on hardness of a Zr-based metallic glass under nanoindentation

Nanoindentation response of laser shock peened Ti-based bulk metallic glass

Nanoindentation in Metallic Glasses

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