The dependence of shear modulus on dynamic relaxation and evolution of local structural heterogeneity in a metallic glass

Huo, Lishan; Zeng, Jianrong; Wang, W.H.; Liu, Chang; Yang, Yong

doi:10.1016/j.actamat.2013.04.004

Cited by 150 publications

(80 citation statements)

References 41 publications

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“…Experimental results (see [21]) already concluded that pure BMGs essentially consist of hard-and soft regions, and such structural heterogeneity will result in the nucleation of a shear transition zone and the subsequent shear-band progression in BMGs. In order to better capture the shear localization, some elements are assigned a slightly lower value of initial free volume, and act as nucleation sites for the initiation of shear bands.…”

Section: Fem Modelingmentioning

confidence: 99%

“…As shown in Figure 1b, the contour plot for the distribution of the initial free volume ν 0 , which was assumed to be statistically varied over the elements, obeying a Gaussian distribution function with a mean value of 0.05, and the standard deviation may be varied. Experimental results (see [21]) already concluded that pure BMGs essentially consist of hard-and soft regions, and such structural heterogeneity will result in the nucleation of a shear transition zone and the subsequent shear-band progression in BMGs. In order to better capture the shear localization, some elements are assigned a slightly lower value of initial free volume, and act as nucleation sites for the initiation of shear bands.…”

Section: Fem Modelingmentioning

confidence: 99%

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Numerical Modeling of Cyclic Deformation in Bulk Metallic Glasses

Jiang

2016

Metals

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Abstract:In this paper, a systematic numerical simulation was performed to elucidate the damage mechanisms in bulk metallic glasses (BMGs) subjected to the tension-compression cyclic loading, and then the relation between fatigue life, applied strain, and cycling frequency was therefore presented. The free volume was selected as an internal state variable to depict the shear-band nucleation, growth, and coalescence with the help of free volume theory, which was incorporated into the ABAQUS code via a user material subroutine UMAT. Under cyclic loading, the shear banding initiation mainly stems from the microstructure inhomogeneity in BMGs and, further, the effect of applied strain amplitude and cycling frequency was discussed. The present simulations will shed some light on the fatigue damage mechanisms and fatigue life evaluation of BMG structures.

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Section: Fem Modelingmentioning

confidence: 99%

Section: Fem Modelingmentioning

confidence: 99%

Numerical Modeling of Cyclic Deformation in Bulk Metallic Glasses

Jiang

2016

Metals

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“…1(b). It should be emphasized that MGs have a continuous distribution of atomic packing patterns [14,47,48]. They should not be misunderstood as real particle-reinforced composite materials.…”

Section: Introductionmentioning

confidence: 99%

“…Although short-and medium-range order may exist in MGs [8][9][10], the lack of a long-range atomic periodicity leads to inherent nanoscale structural heterogeneity. Both experiments [11][12][13][14][15][16] and atomic simulations [4,[17][18][19] have verified structural heterogeneity in MGs. Pioneering works have described this heterogeneity as solidlike and liquidlike regions [12,[20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Strain gradient drives shear banding in metallic glasses

et al. 2017

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Strain gradient drives shear banding in metallic glassesShear banding is a nucleation-controlled process in metallic glasses (MGs) involving multiple temporal-spatial scales, which hinders a concrete understanding of its structural origin down to the atomic scale. Here, inspired by the morphology of composite materials, we propose a different perspective of MGs as a hard particle-reinforced material based on atomic-scale structural heterogeneity. The local stable structures indicated by a high level of local fivefold symmetry (L5FS) act as hard "particles" which are embedded in the relatively soft matrix. We demonstrate this concept by performing atomistic simulations of shear banding in CuZr MG. A shear band is prone to form in a sample with a high degree of L5FS which is slowly quenched from the liquid. An atomic-scale analysis on strain and the structural evolution reveals that it is the strain gradient effect that has originated from structural heterogeneity that facilitates shear transformation zones (STZs) to mature shear bands. An artificial composite model with a high degree of strain gradient, generated by inserting hard MG strips into a soft MG matrix, demonstrates a great propensity for shear banding. It therefore confirms the critical role strain gradient plays in shear banding. The strain gradient effect on shear banding is further quantified with a continuum model and a mechanical instability analysis. These physical insights might highlight the strain gradient as the hidden driving force in transforming STZs into shear bands in MGs.

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“…Following this line of reasoning, one may picture that plastic flow in disordered solids should be caused by the percolation of the local flow defects. This is a scenario that can be envisioned based on the view that disordered solids are intrinsically heterogeneous [17][18][19], containing soft spots or local regions of significant "physical softness".…”

mentioning

confidence: 99%