A study of mechanical homogeneity in as-cast bulk metallic glass by nanoindentation

Plummer, John; Goodall, Russell; Figueroa, I.A.; Todd, Iain

doi:10.1016/j.jnoncrysol.2010.11.002

Cited by 15 publications

(8 citation statements)

References 20 publications

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“…The lower number of pop-in events during nanoindentation on the NW plane than on the NR and RW planes indicates a low number of shear band activation and their propagation. Such reduced pop-in events due to the cooling rate difference between the sample surfaces and interior portion of Zr-based BMG rods have been observed earlier [ 42 ]. Likewise, all the cold rolled samples have shown similar behavior on the different planes at a given cold rolling strain.…”

Section: Resultssupporting

confidence: 68%

Effect of Cold Rolling on the Evolution of Shear Bands and Nanoindentation Hardness in Zr41.2Ti13.8Cu12.5Ni10Be22.5 Bulk Metallic Glass

et al. 2021

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The effect of cold rolling on the evolution of hardness (H) and Young’s modulus (E) on the rolling-width (RW), normal-rolling (NR), and normal-width (NW) planes in Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vitreloy 1) bulk metallic glass (BMG) was investigated systematically using nanoindentation at peak loads in the range of 50 mN–500 mN. The hardness at specimen surface varied with cold rolling percentage (%) and the variation is similar on RW and NR planes at all the different peak loads, whereas the same is insignificant for the core region of the specimen on the NW plane. Three-dimensional (3D) optical surface profilometry studies on the NR plane suggest that the shear band spacing decreases and shear band offset height increases with the increase of cold rolling extent. Meanwhile, the number of the pop-in events during loading for all the planes reduces with the increase of cold rolling extent pointing to more homogeneous deformation upon rolling. Calorimetric studies were performed to correlate the net free volume content and hardness in the differently cold rolled specimens.

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Section: Resultssupporting

confidence: 68%

Effect of Cold Rolling on the Evolution of Shear Bands and Nanoindentation Hardness in Zr41.2Ti13.8Cu12.5Ni10Be22.5 Bulk Metallic Glass

et al. 2021

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“…Whereas those studies have offered insight into the details of the atom rearrangement under an imposed shear stress for specific interatomic potentials, the system sizes are small and the strain rates are exceedingly high so that the direct application of the findings to actual experimental conditions is somewhat unclear. Moreover, recent experimental studies have revealed the presence of nanoscale spatial heterogeneities in amorphous alloys that have not been considered in the simulations, but may affect deformation (21)(22)(23)(24)(25)(26).…”

mentioning

confidence: 99%

Nucleation of shear bands in amorphous alloys

Perepezko

Imhoff

Chen

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

107

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The initiation and propagation of shear bands is an important mode of localized inhomogeneous deformation that occurs in a wide range of materials. In metallic glasses, shear band development is considered to center on a structural heterogeneity, a shear transformation zone that evolves into a rapidly propagating shear band under a shear stress above a threshold. Deformation by shear bands is a nucleation-controlled process, but the initiation process is unclear. Here we use nanoindentation to probe shear band nucleation during loading by measuring the first pop-in event in the load-depth curve which is demonstrated to be associated with shear band formation. We analyze a large number of independent measurements on four different bulk metallic glasses (BMGs) alloys and reveal the operation of a bimodal distribution of the first pop-in loads that are associated with different shear band nucleation sites that operate at different stress levels below the glass transition temperature, T g . The nucleation kinetics, the nucleation barriers, and the density for each site type have been determined. The discovery of multiple shear band nucleation sites challenges the current view of nucleation at a single type of site and offers opportunities for controlling the ductility of BMG alloys.plastic deformation | stochastic analysis D eformation by shear bands occurs in both crystalline and amorphous phases over a wide range of size scales. In geological materials with a granular nature such as sand (1, 2) or within rocks, shear bands are of macroscopic size (3); in polymers and crystalline metals, shear bands are several micrometers in size; in metallic glasses (MGs), shear bands are of the order of 10-20 nm in thickness (4). The onset of shear bands in metallic glasses represents initial plastic yielding and induces a highly localized plastic flow that limits ductility and is responsible for strain softening (4, 5). Because shear bands directly determine the capability of an amorphous phase to sustain plastic flow and exhibit ductile behavior, there have been numerous studies on the propagation of shear bands to promote shear band branching and additional nucleation to achieve useful ductility (6-9). On a microscopic scale, the initiation of shear bands in MGs is considered to be controlled by the activation of a shear transformation zone (STZ) (10, 11) that represents a localized atomic arrangement. The STZs are activated by a two-stage process starting with a flow-induced dilatation that broadens homogeneously in the initial stage, but subsequently narrows into a shear band autocatalytically at the expense of shear flow in the surrounding material (10, 12). The localization of plastic flow would become predominant at low temperatures because the diffusive atomic rearrangements are too slow to disperse the dilatation effect quickly enough. Clearly, the nucleation of shear bands is of critical importance in the deformation behavior, but the detailed examination of the nucleation kinetics behavior has received only limited s...

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“…The indentation instrument used in this paper was developed by our group but the phenomenon shown in figure 1(a) generally exists in load-displacement curves obtained by some other indentation instruments [14][15][16][17][18][19][20]. In this section, a simple description of our indentation instrument will be given first and then emphasis will be focused on analysis of the possible reasons leading to the shape of the load-displacement curve as shown in figure 1(a).…”

Section: The Custom-made Indentation Instrument and Analysismentioning

confidence: 99%

“…The inflection affected determination of the residual indentation depth [13] and further affected the calculation result. In order to obtain the reason, we checked the literature and found that it was a typical type of load-displacement curve that was discussed in some published papers [14][15][16][17][18][19][20]. However, the reason is not very clear.…”

Section: Introductionmentioning

confidence: 99%

Large Volume Coagulation Utilizing Multiple Cavitation Clouds Generated by Array Transducer Driven by 32 Channel Drive Circuits

Nakamura

Asai

Sasaki

et al. 2013

Jpn. J. Appl. Phys.

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The results of nanoindentation testing strongly rely on load-displacement curves, but an abnormal load-displacement curve with obvious inflection in the unloading portion was commonly observed in previously published papers and the reason is not clear. In this paper, possible reasons involved in a custom-made indentation instrument, such as sensors, control and assembly issues, are analyzed and discussed step by step. Experimental results indicate that non-ideal assembly of the precision driving unit strongly affects the shape of the load-displacement curve and its affecting mechanism is studied by theoretical analysis and finite element simulations. This paper reveals the reason leading to the abnormal load-displacement curve, which is helpful for debugging of indentation instruments and can enhance comparability of indentation results.

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A study of mechanical homogeneity in as-cast bulk metallic glass by nanoindentation

Cited by 15 publications

References 20 publications

Effect of Cold Rolling on the Evolution of Shear Bands and Nanoindentation Hardness in Zr41.2Ti13.8Cu12.5Ni10Be22.5 Bulk Metallic Glass

Effect of Cold Rolling on the Evolution of Shear Bands and Nanoindentation Hardness in Zr41.2Ti13.8Cu12.5Ni10Be22.5 Bulk Metallic Glass

Nucleation of shear bands in amorphous alloys

Large Volume Coagulation Utilizing Multiple Cavitation Clouds Generated by Array Transducer Driven by 32 Channel Drive Circuits

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