Indentation size effect in FCC metals: An examination of experimental techniques and the bilinear behavior

Stegall, David E.; Mamun, Md. Abdullah Al; Crawford, B.; Elmustafa, A. A.

doi:10.1557/jmr.2012.91

Cited by 23 publications

(10 citation statements)

References 33 publications

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“…3 and 4, our experiments revealed a clear bilinear behavior and an overestimation of the hardness values using the Nix-Gao description. Such an overestimation in the low depth regime could be related to the dynamic measurement [30][31][32] or a blunt tip [9]. However, the same effect was observed for quasi-static indentation experiments (Fig.…”

Section: Modeling Of the Bilinear Indentation Size Effectsupporting

confidence: 56%

The indentation size effect of single-crystalline tungsten revisited

Wang

Volz

Weygand

et al. 2021

Journal of Materials Research

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In this study, we have investigated the indentation size effect (ISE) of single crystalline tungsten with low defect density. As expected, the hardness shows a pronounced increase with decreasing indentation depth as well as a strong strain rate dependence. For penetration depths greater than about 300 nm, the ISE is well captured by the Nix–Gao model in the context of geometrically necessary dislocations. However, clear deviations from the model are observed in the low depth regime resulting in a bilinear effect. The hardness behavior in the low depth regime can be modeled assuming a non-uniform spacing of the geometrically necessary dislocations. We propose that the bilinear indentation size effect observed reflects the evolution of the geometrically necessary dislocation density. With increasing strain rate, the bilinear effect becomes less pronounced. This observation can be rationalized by the activation of different slip systems. Graphic abstract

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Section: Modeling Of the Bilinear Indentation Size Effectsupporting

confidence: 56%

The indentation size effect of single-crystalline tungsten revisited

Wang

Volz

Weygand

et al. 2021

Journal of Materials Research

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“…A newly developed inverse method [30] for isotropic materials is used to determine the nominal yield strength and nominal strain hardening exponent. The ISE is considered since the characteristic length ( ) of Ag estimated through the Nix-Gao model [38] has been reported as 450 nm from previous studies [53,54], and the current indentation depths were less than 400 nm. Generally, the origin of ISE was considered as the dislocation density within materials beneath the indenter [38] Hereafter, and will be used instead of and as the un-determined parameters since the sum of the actual yield strength in the two directions ( ) can be approximated by the sum of the nominal yield strength ( ), and this assumption did not lead to significant difference on the final flow stress in the previous study of NiAl coating [11].…”

Section: Nominal Properties For L and T Directionsmentioning

confidence: 99%

Nanoindentation study of electrodeposited Ag thin coating: An inverse calculation of anisotropic elastic-plastic properties

Cheng

Wang

et al. 2017

Surface and Coatings Technology

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A new inverse method was proposed to calculate the anisotropic elastic-plastic properties (flow stress) of electrodeposited Ag thin coating utilizing nanoindentation tests, previously reported inverse method for isotropic materials and three-dimensional (3-D) finite element analyses (FEA). Indentation depth was ~4% of coating thickness (~10 μm) to avoid substrate effect and different indentation responses were observed in the longitudinal (L) and the transverse (T) directions. The estimated elastic-plastic properties were obtained in the newly developed inverse method by matching the predicted indentation responses in the L and T directions with experimental measurements considering indentation size effect (ISE). The results were validated with tensile flow curves measured from free-standing (FS) Ag film. The current method can be utilized to characterize the anisotropic elastic-plastic properties of coatings and to provide the constitutive properties for coating performance evaluations.

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“…As mentioned earlier, the indentation depth was ~300 nm, and the strong indentation size effect (ISE) could be expected considering the thin nature of the Ag-Bi coating. Thus, we first removed the ISE based on the characteristic length (

= 450 nm [ 49 , 50 ]) for the electrodeposited Ag-Bi coating. It should be noted that the target load values for the simulation are

rather than 5 mN [ 51 ].…”

Section: Resultsmentioning

confidence: 99%

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

et al. 2017

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In this study we investigated the effects of Bi addition on the microstructure and mechanical properties of an electrodeposited nanocrystalline Ag coating. Microstructural features were investigated with transmission electron microscopy (TEM). The results indicate that the addition of Bi introduced nanometer-scale Ag-Bi solid solution particles and more internal defects to the initial Ag microstructures. The anisotropic elastic-plastic properties of the Ag nanocrystalline coating with and without Bi addition were examined with nanoindentation experiments in conjunction with the recently-developed inverse method. The results indicate that the as-deposited nanocrystalline Ag coating contained high mechanical anisotropy. With the addition of 1 atomic percent (at%) Bi, the anisotropy within Ag-Bi coating was very small, and yield strength of the nanocrystalline Ag-Bi alloy in both longitudinal and transverse directions were improved by over 100% compared to that of Ag. On the other hand, the strain-hardening exponent of Ag-Bi was reduced to 0.055 from the original 0.16 of the Ag coating. Furthermore, the addition of Bi only slightly increased the electrical resistivity of the Ag-Bi coating in comparison to Ag. Results of our study indicate that Bi addition is a promising method for improving the mechanical and physical performances of Ag coating for electrical contacts.

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Indentation size effect in FCC metals: An examination of experimental techniques and the bilinear behavior

Abstract: Abstract

Cited by 23 publications

References 33 publications

The indentation size effect of single-crystalline tungsten revisited

The indentation size effect of single-crystalline tungsten revisited

Nanoindentation study of electrodeposited Ag thin coating: An inverse calculation of anisotropic elastic-plastic properties

Effects of Bi Addition on the Microstructure and Mechanical Properties of Nanocrystalline Ag Coatings

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