Room Temperature Homogeneous Ductility of Micrometer‐Sized Metallic Glass

Tönnies, Dominik; Maaß, R.; Volkert, Cynthia A.

doi:10.1002/adma.201401123

Cited by 73 publications

(48 citation statements)

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“…2a. Moreover, this also agrees well with the lower m observed under macro-compression [32] than micro-pillar compression [33]. When the peak-load increases to larger than a critical value, the overall unstable plastic flow (the advent of a mature shear band) will occur immediately once the indenter presses into the metallic glass [20].…”

Section: Contents Lists Available At Sciencedirectsupporting

confidence: 76%

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 Sciencedirectsupporting

confidence: 76%

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

Jiang

et al. 2017

Scripta Materialia

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“…The shear offsets seen on the pillars' surfaces in the accompanying micrographs suggest that the pop-ins in these stress-strain curves correspond to shear banding events. That these pillars deform by shear localization is consistent with past reports on the microcompression testing of metallic glass pillars with diameters [1 lm [41][42][43][44]. In most tests, only a single pop-in was observed, followed by pillar failure but occasionally tests captured multiple pop-in events, separated by regions of continued elastic deformation.…”

Section: Resultssupporting

confidence: 78%

“…In light of other studies on taper-free metallic glass pillars with similar dimensions, this yield strength would likely match that of bulk specimens if such specimens could be prepared [25,26,44]. The other phenomena seen in these microcompression tests are consistent with prior studies on the microcompression testing of metallic glasses, confirming that microcompression testing of powder particles can be used to extract a powder's intrinsic deformation behavior.…”

Section: Resultssupporting

confidence: 75%

Micropillar compression testing of powders

et al. 2015

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An experimental design for microcompression on individual powder particles is proposed as a means of testing novel materials without the challenges associated with consolidation to produce bulk specimens. This framework is demonstrated on an amorphous tungsten alloy powder, and yields reproducible measurements of the yield strength (4.5 ± 0.3 GPa) and observations of the deformation mode (in this case, serrated flow by shear localization).

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“…Very recently, Volkert et al [24] revealed that SRS kept constant among the samples with different sizes, indicating the same underlying mechanism in both localized and homogeneous deformation. This implies that the STZs play an important role on the apparent size effect of plastic deformation in metallic glasses.…”

Section: Introductionmentioning

confidence: 96%