Characterization of nanoindentation damage in metal/ceramic multilayered films by transmission electron microscopy (TEM) (original) (raw)
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High-temperature nanoindentation behavior of Al/SiC multilayers
Philosophical Magazine Letters, 2012
Nanoscale Al/SiC composite laminates have unique properties, such as high strength, high toughness, and damage tolerance. In this article, the high-temperature nanoindentation response of Al/SiC nanolaminates is explored from room temperature up to 300 C. Selected nanoindentations were analyzed postmortem using focused ion beam and transmission electron microscopy to ascertain the microstructural changes and the deformation mechanisms operating at high temperature.
Delamination analysis of metal–ceramic multilayer coatings subject to nanoindentation
Surface and Coatings Technology, 2016
Internal damage has been experimentally observed in aluminum (Al)/silicon carbide (SiC) multilayer coatings subject to nanoindentation loading. Post-indentation characterization has identified that delamination at the coating/substrate interface is the most prominent form of damage. In this study the finite element method is employed to study the effect of delamination on indentation-derived hardness and Young's modulus. The model features alternating Al/SiC nanolayers above a silicon (Si) substrate, in consistence with the actual material system used in earlier experiments. Cohesive elements with a traction-separation relationship are used to facilitate delamination along the coating/substrate interface. Delamination is observed numerically to be sensitive to the critical normal and shear stresses that define the cohesive traction-separation behavior. Axial tensile stress below the edge of indentation contact is found to be the largest contributor to damage initiation and evolution. Delamination results in a decrease in both indentation-derived hardness and Young's modulus. A unique finding is that delamination can occur during the unloading process of indentation, depending on the loading condition and critical tractions.
Acta Materialia, 2010
The behavior of aluminum/silicon carbide nanolayered composite in response to nanoindentation loading is studied. The effects of heterogeneity on the deformation fields, as well as the hardness and elastic modulus obtained from indentation, are investigated using finite element analysis. Attention is also devoted to correlating the numerical results with experimental deformation and damage features. The model uses an explicit layered structure within the axisymmetric framework. It is found that the nanolayered composite results in unique deformation patterns. Significant tensile stresses can be generated locally along certain directions, which offers a mechanistic rationale for the internal cracking observed experimentally. The unloading process also leads to an expansion of the tension-stressed area, as well as continued plastic flow in parts of the aluminum layers. Comparisons of hardness and indentation-derived modulus between modeling and experiments also point to the importance of incorporating the detailed geometric features when performing indentation analyses.
Indentation mechanics and fracture behavior of metal/ceramic nanolaminate composites
Journal of Materials Science, 2008
Composite laminates on the nanoscale have unique properties, such as high strength, high wear resistance, and biocompatibility. In this paper we report on the nanoindentation behavior of a model metal-ceramic nanolaminate consisting of alternating layers of aluminum and silicon carbide (Al/SiC) processed by PVD on a Si substrate. Composites with different layer thicknesses were fabricated and the effect of layer thickness on Young's modulus and hardness was quantified. The effect of indentation depth on modulus and hardness was studied. The damage that took place during nanoindentation was examined by cross-sectioning the samples by focused ion beam (FIB) technique and imaging the surface using scanning electron microscopy (SEM). Finite element modeling (FEM) of nanoindentation of nanolaminates was conducted. The damage patterns observed in experiments were qualitatively supported by the numerical simulations.
Cyclic indentation behavior of metal-ceramic nanolayered composites
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing, 2012
The indentation behavior of metal/ceramic nanolayered composites is studied numerically using the finite element method. Attention is devoted to cyclic response under fixed maximum and minimum loads, with the primary objective of examining the evolving plastic deformation in the ductile metal constrained by the hard ceramic layers. The axisymmetric model consists of alternating aluminum (Al) and silicon carbide (SiC) thin films on a silicon (Si) substrate, with the Al/SiC layered structure indented by a conical diamond indenter. It is found that, unlike the homogeneous material where indentation unloading consists of purely elastic recovery, in the multilayered material plastic deformation in the Al layers continues to occur upon unloading and subsequent loading/unloading operations. With each additional cycle the indenter penetrates deeper into the composite. The modeling results are in qualitative agreement with the actual cyclic nanoindentation experiment conducted on the Al/SiC nanolayers.
International Journal of Applied Ceramic Technology, 2018
The elastic-plastic deformation of 3C-SiC thin film was investigated by a nanoindenter equipped with the Berkovich tip. Transition from pure elastic to elastic-plastic deformation was evidenced at an approximate load of 0.35 mN, when loading the sample at several peak loads ranging from 0.5 to 5mN. The indentation size effect observed in 3C-SiC and was Accepted Article This article is protected by copyright. All rights reserved. analyzed by Nix-Gao model. In purely elastic region, the Oliver-Pharr hardness values were 44 ± 2 GPa. In contrast, indentation size effects were evidenced in 3C-SiC specimen and the average value of Oliver-Pharr hardness in the indentation size effect region was 36 ± 2 GPa. Furthermore, depth independent or intrinsic hardness extracted from Nix-Gao was estimated as H o = 26 ± 1 GPa which was also validated by proportional specimen resistance model i.e., H 1 = 28 ± 1 and H 2 = 28.5 0.1 GPa. Besides, energy principle was utilized to extract Sakai Hardness as 104 GPa, which is combined elastic and elastic-plastic response. Moreover, based on energy principle, another property i.e., work of indentation was also determined to be 20 nJ/µm 3. Similarly, elastic modulus had almost depicted stabilized value of 325 ± 8 GPa in pure elastic and elastic-plastic regions. In addition, plastic zone size was also estimated in elastic-plastic region using Johnson cavity model at pop-in and higher loads. Based on the first pop-in load at 0.35 mN, the distributions of shear and principal stresses were evaluated on various slip planes to elaborate the deformation behavior. Increase in loading rate from 100 to 400µN/s increased critical pop-in load from 0.35 to 0.64 mN. This increase in critical pop-in load with increasing loading rate and values of maximum contact pressure indicates that no phase assisted transformation will occur at pop-in load. Based on theoretically calculated maximum tensile and cleavage strengths, it was affirmed that the elastic-plastic deformation occurred due to pop-in formation rather than tensile stresses. Moreover, it was also concluded on basis of Hertzian contact theory and Schmidt law that the highest possibility of slippage in 3C-SiC was along the glide plane.
Residual stress characterization of Al/SiC nanoscale multilayers using X-ray synchrotron radiation
Thin Solid Films, 2010
Nanolayered composites are used in a variety of applications such as wear resistant coatings, thermal barrier coatings, optical and magnetic thin films, and biological coatings. Residual stresses produced in these materials during processing play an important role in controlling their microstructure and properties. In this paper, we have studied the residual stresses in model metal-ceramic Al/SiC nanoscale multilayers produced by physical vapor deposition (magnetron sputtering). X-ray synchrotron radiation was used to measure stresses in the multilayers using the sin 2 Ψ technique. The stresses were evaluated as a function of layer thicknesses of Al and SiC and also as a function of the number of layers. The stress state of Al in the multilayer was largely compressive, compared to single layer Al stresses. This is attributed to a peening mechanism due to bombardment of the Al layers by SiC and Ar neutrals during deposition. The stress evolution was numerically modeled by a simplified peening process to qualitatively explain the Al thickness-dependent residual stresses.
High-Temperature Nanoindentation of SiC/SiC Composites
JOM, 2019
The results of high-temperature nanoindentation testing on both a control and a neutron-irradiated silicon carbide matrix silicon carbide fiber composite sample are presented. The mechanical properties of the chemical vapor-infiltrated matrix were observed to have slightly increased in hardness and slightly decreased in elastic modulus after irradiation. Tyranno SA3 fiber behavior results are inconclusive, possibly because residual graphite in the fibers resulting from the manufacturing process produced a large scatter in the data. This work also demonstrates the capability to measure the individual components of fabricated composites at elevated temperature, which should provide inputs for modeling the macro-scale behavior of the composites. JOM
Journal of Advanced Ceramics, 2021
Scanning electron microscopy shows that the microstructure, in particular the overall grain size, of chemical vapor deposited silicon carbide coatings depends on the deposition temperature. So far, the influence of the microstructure on the mechanical properties of such coatings is not well described in literature. To investigate the influence of the deposition temperature on the mechanical properties of the coating, nanoindentation is used in this work. Since the measurement results of nanoindentation can be affected by the substrate material, the contribution of the substrate material is taken into account utilizing a finite element model. The model is then employed to generate information about elastic and plastic properties of the coating by inverse simulation. To evaluate the fracture toughness of the coating, the generated material model is used in a cohesive-zone based formulation of the fracture process during indentation at higher loads. The results of this model allow dete...