Depth-sensing Indentation Measurements Research Articles

Influence of Multilayer Structure on the Structural and Mechanical Properties of TiAlN/CrN Coatings for Advanced Machining Applications

This study investigates single and multilayer TiAlN/CrN nanocomposite thin films developed using an RF magnetron sputtering system. The TiAlN and CrN layers showed a high degree of orientation, with the (200) peak being the strongest peak in both layers, and a multilayer structure was clearly observed. The surface roughness analysis using atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (TEM) revealed that the TiAlN/CrN coatings had a smoother surface than the single-layer coatings and minimal intermixing between the two layers. Depth-sensing indentation measurements were used to measure the hardness and Young’s modulus of the coatings, demonstrating that TiAlN/CrN coating had the highest hardness (~16.38 GPa) and elastic modulus (~3.82 GPa) among all the coatings studied. This indicates that the TiAlN/CrN multilayer coating possesses superior mechanical properties due to its interface strength. Our findings suggest that these multilayer coatings have potential applications in tribological and decorative coatings.

DIC/DSI based studies on the local mechanical behaviors of HR3C/T92 dissimilar welded joint during plastic deformation

In this study, both the digital image correlation (DIC) and depth-sensing indentation (DSI) measurements were performed to investigate the non-uniform local mechanical behaviors of HR3C/T92 dissimilar welded joint during plastic deformation. The macro-scale DIC experiments showed the uneven distribution and transfer phenomena of the plastic deformation in the welded samples. The grain-scale DIC measurements further revealed that the strain localization was closely related to the local microstructures. To understand the correlation of the non-uniform deformation behavior with the local microstructure in the welded samples, the electron backscatter diffraction (EBSD) tests in the as-received state and ex-situ optical microscope (OM) observations during the tensile deformation process were conducted. The slip morphologies were found to be different across the welded joint, and the grain-scale strain localizations were proved to be closely related with the behaviors of the slip bands. Moreover, ex-situ DSI tests were also carried out to determine the local mechanical properties of the HR3C/T92 dissimilar welded joint during the tensile deformation process. The basic elasto-plastic properties (elastic modulus, yield strength, and hardening parameters) in particular zones of the welded joint were estimated by using the multi-fidelity deep neural network method combined with indentation characteristic parameters. The non-uniform deformation behavior of the HR3C/T92 welded joint during tensile loading was further simulated by using the finite element method based on the estimated elasto-plastic properties of the welded joint, and a general agreement between the simulated result and experimental tensile curve has been obtained.

Understanding the relationship between microstructure and mechanical behavior of plasma-sprayed amorphous Al2O3–YAG ceramic coating based on depth-sensing indentation measurements

Understanding the relationship between microstructure and mechanical behavior of plasma-sprayed amorphous Al2O3–YAG ceramic coating based on depth-sensing indentation measurements

Quasi-static and dynamic depth-sensing indentation measurements to characterize wear and mar resistance of coating–polymer systems

Abstract Different layers of different thicknesses were coated on the same polymethyl methacrylate (PMMA) substrate. For each of these bilayered systems, quasi-static and dynamic instrumented indentations using continuous stiffness measurement have been made. We verified if data from indentation tests performed on a given sample obey a power law relationship. The aim was to calculate the viscoplasticity index n with sufficient accuracy (by taking into account the viscoelastoplastic properties of the studied samples), since this value is characteristic of the viscoplastic properties of a material and, therefore, allows evaluating the plastic scratch resistance of the surface. Thanks to both indentation methods the viscoplasticity index could be calculated and its value compared to the different bilayered systems one. As n is supposed to be intrinsic to a material, its value should not depend on the characterization technique.

Mechanical properties of neutron-irradiated single crystal tungsten W(100) studied by indentation and FEM modelling

The aim of this work is to investigate the effect of high-temperature neutron irradiation on the mechanical properties of single-crystal tungsten W(100) studied by mechanical testing and modelling. Neutron irradiation up to 0.12 displacements per atom was performed at 600, 800, 900 and 1200 °C in the Belgium material test reactor BR2 at SCK•CEN in Mol. The mechanical properties of the irradiated tungsten were assessed by impulse excitation and depth-sensing indentation measurements. The values of Young's modulus, shear modulus and Poisson ratio are not affected by the irradiation. The mean hardness of the irradiated tungsten increases by 48, 45, 46, and 34% after irradiation at 600, 800, 900 and 1200 °C, respectively. The results obtained by the instrumented hardness tests were used as input for the finite element method model, applied to deduce the contributions coming from the neutron irradiation defects to the plastic deformation upon the indentation process, which include the impediment of gliding dislocations by sessile defects and modification of surface morphology due to the inhibited strain hardening ability through the dislocation-defect interaction. The validation of the fitted constitutive laws was realized by the crystal plasticity finite element method (CP-FEM) model which was applied to simulate the indentation load-depth curves, with certain assumptions on the irradiation-induced microstructure, and to calculate the distribution of stress under the indenter to investigate the extension of the plastic zone in the process of the indentation.

Assessing mechanical behavior of ostrich and equine trabecular and cortical bone based on depth sensing indentation measurements

Guided bone regeneration surgeries are based on grafting a scaffold in the site to be repaired. The main focus of the scaffold is to provide mechanical support to newly formed blood vessels and cells that will colonize the grafted site, achiving bone regenertation. In this regards, the aim of this study was to characterize the anatomy, structular, surface morphologycal, chemical composition, and nanomechanical properties of ostrich and equine trabecular bone. Ostrich and equine specimens were obtained from a local abattoir and bone was obtained by blunt dissection, n = 5. Tissue bone anatomy and trabecular structure were measured using Computerized Axial Tomography (CAT). Atomic Force Microscopy (AFM) and Energy dispersion spectrometry of X-ray (EDS) were used to examine surface morphology and chemical composition of the trabecular ostrich and equine bone. Mechanical behavior was analysted by nanoindentation. Equine specimens were examined as control. CAT results suggest that in terms of anthropometry, ostrich tarsometatarsus bone is more suitable due to its length is 432.56 ± 3.12 mm vs. the highest human bone structures reported, which femur length is 533.66 ± 18.81 mm. Besides, the low radiodensity in the Hounsfield scale exhibits equine trabecular bone more brittle (Av = 1538.4 ± 0.9) than ostrich trabecular bone (Av = 462.1 ± 1.5). EDS showed a slight variation of the element Calcium (Ca2+) ranging from 20% to 25.5% wt in equine bone; the Ca2+ content variation is consistent with the ring-shaped morphology, while in ostrich bone the chemical composition is homogeneous. The elastic modulus, nanohardness (E = 5.3 ± 0.7 GPa, H = 220 ± 10 MPa) and average roughness (Ra = 207 nm) are similar to the human trabecular bone which could reduce the stress shielding, all of these findings suggest that ostrich bone can be promising for native tissue scaffolds for mechanically demanding applications. This research makes innovative contributions to science and provides a framework, which will allow us to address future biomedical tests, and rapidly identify promising organic and sustainable waste for tissue scaffold.

Extended Applications of the Depth-Sensing Indentation Method.

The depth-sensing indentation method has been applied for almost 30 years. In this review, a survey of several extended applications developed during the last three decades is provided. In depth-sensing indentation measurements, the load and penetration depth data are detected as a function of time, in most cases at controlled loading rates. Therefore, beside the determination of hardness and Young’s modulus, different deformation mechanisms and many other dynamic characteristics and phenomena, such as the dynamic elastic modulus, load-induced phase transition, strain rate sensitivity, etc. can be studied. These extended applications of depth-sensing indentation measurements are briefly described and reviewed.

Nanomechanical Behaviour of Martensite in Cryogenically Deformed NiTi Alloy

Effect of ageing treatment on work-hardening response of cryogenically deformed martensitic NiTi alloy has been evaluated at the microstructural length scale by conducting nanoindentation or depth-sensing instrumented indentation measurements. Hardening response has been observed in the alloy sample by cyclic indentation. Nanomechanical properties, viz. nanohardness, hardness to elastic modulus (H/E) ratio, and recovery index, were estimated at peak-aged condition.

Unprecedented dependence of stiffness parameters and crystallinity on comonomer content in rapidly cooled propylene-co-1-pentene copolymers

A thorough evaluation of the mechanical behavior exhibited by fast crystallized propylene-1-pentene copolymers, synthesized in a broad range of 1-pentene compositions, is here described. Different mechanical magnitudes derived from loading, creep and unloading processes in depth sensing indentation measurements are correlated to structural features. Several ordered forms are able to be developed applying a fast cooling processing at the composition interval analyzed in these propylene-1-pentene copolymers. Moreover, either a single polymorph or distinct ratios of two crystalline lattices can be obtained, depending on comonomer content. Crystallinity as well as the type of existing crystallites play a critical role in the value of those mechanical magnitudes. An uncommon dependence of either crystallinity or stiffness on 1-pentene content is observed in these copolymers, associated with their capability of crystallizing in the trigonal form.

Stress–strain characteristic of human trabecular bone based on depth sensing indentation measurements

In the paper a relation between stress and strain for trabecular bone is presented. The relation is based on the results of depth sensing indentation (DSI) tests which were performed with a spherical indenter. The DSI technique allowed also to determine three measures of hardness, i.e. Martens hardness (HM), nanohardness (HIT), Vickers hardness (HV) and Young modulus EIT of the trabecular bone tissue. The bone samples were harvested from human femoral heads during orthopaedical procedures of hip joint implantation.In the research the Hertzian approach is undertaken. The constitutive relation is then formulated in the elastic domain. The values of hardness and the Young modulus obtained from the DSI tests are in good agreement with those found in literature. The stress–strain relation is formulated to implement it in the future in finite element analyses of trabecular bone. Such simulations allow to take into account the microstructural mechanical properties of the trabecular tissue as well as remodelling phenomenon. This will make it possible to analyse the stress and strain states in bone for engineering and medical purposes.

Scratch- and wear-resistant photoluminescent silicone epoxy coatings on floor tiles

Photoluminescent silicone epoxy resins were prepared by physical dispersion of SrAl2O4:Eu2+, Dy3+ pigments. The resin was deposited on ceramic tiles for flooring by automatic drawdown and left to harden at ambient conditions. Morphology of the coated tiles was measured by contact gage profilometry and field emission gun scanning electron microscopy. Mechanical response was investigated by pencil and cross-hatch scratch tests; depth-sensing indentation measurements were performed using Vickers and flat punch indenters. Tribological response of the coated tiles was measured by progressive and constant load scratch tests and dry sliding linearly reciprocating ball-on-flat tests, respectively. Intensity of photoluminescent radiations and the corresponding decay time were estimated by digital imaging. The photoluminescent coatings feature high hardness, scratch and wear endurance as well as good clarity. Being the resin designed for spontaneous drying and suitable for easy-to-automate and versatile deposition processes, it is the ideal candidate for the decoration of a large variety of substrates as well as for the repowering and/or retrofitting of previous installations.

Mechanical characterisation of virgin and recovered polycarbonate based nanocomposites by means of Depth Sensing Indentation measurements

The preparation of recovered polycarbonate matrix nanocomposites filled with organic modified montmorillonites has been considered as a method for the secondary or mechanical recycling of these polymeric wastes. The mechanical properties of these nanocomposites have been evaluated by means of Depth Sensing Indentation measurements. The selection of the measurement conditions has been discussed and a method to evaluate the heterogeneity of these materials has been presented. It has been found that greater nanoclay contents do not always lead to increase in mechanical properties. This fact has been explained in terms of the competition between the reinforcement effect of the nanofiller and the thermal and mechanical degradation that experiments the matrix during the melt processing. This result provide a limit for the clay addition in the mechanical recovery of polycarbonate wastes.

Thermal stability and mechanical properties of the TiCuZrPd glasses with 10, 14 and 20 at.% Pd

Metallic glasses of the composition Ti40Zr10Cu40−xPd10+x with x=0, 4 and 10, were investigated from the point of view of the thermal stability, crystallization and hardness. The samples in the form of melt spun ribbons and rods 2.8mm in diameter, were characterized by differential scanning calorimetry (DSC), Thermo-Mechanical Analysis (TMA), macro-Vickers hardness (MHv10) and depth-sensing indentation measurements. The TMA experiments were performed on ribbons in the modulated constant load tensile mode. The processes of relaxation, glass transition and crystallization were observed with DSC and transmission electron microscopy (TEM). The relative length changes rates as a function of temperature (dL/dTL0) showed influence of the thermal stability of the amorphous phase on the materials ductility. High ductility was available in the wide range of temperature including primary crystallization range. Vickers-macrohardness of BMG was about 5500MPa and nanohardness was about 9300MPa, increasing after crystallization completion by about 18%. At small nanoindentation rates deformed amorphous phase revealed local plastic instability resulting from the shear bands formation.

Ex-situ depth-sensing indentation measurements of electrochemically produced Si–Li alloy films

We report for the first time ex-situ measurements of the Young's modulus and hardness of Si and Si–Li alloy thin film electrodes at various stages of lithium insertion via depth-sensing indentation experiments. Lithium is electrochemically inserted into the Si electrode, after which its mechanical properties are investigated in an anoxic environment. The Young's modulus was found to decrease from an initial value of 92 GPa for pure Si to 12 GPa at full lithium insertion (Li 15Si 4). The hardness changes from an initial value of 5 GPa for Si to 1.5 GPa for Li 15Si 4.

Tip bluntness transition measured with atomic force microscopy and the effect on hardness variation with depth in silicon dioxide nanoindentation

Depth-sensing indentation measurements of surfaces and structures with indentation depths less than 100 nm necessitate the use of accurate area functions for correct property evaluation. Here, the effect of a blunt nanoindenter tip geometry is characterized using atomic force microscopy to measure the direct tip geometry and modeled by a power law profile shape. Direct measurement of tip geometry is a method to observe changes in the tip curvature and transition from the blunt tip region to an ideal tip geometry. The tip shape, curvature, and transition to ideal geometry is found to correspond with the increase in hardness observed experimentally in SiO2 using a self-similar contact model. For a Berkovich indenter, tip bluntness was found to have a power law degree of 1.5 near the tip apex with a continuously varying degree of bluntness until an ideal pyramidal shape was reached at a depth of 160 nm.

Indentation modulus and hardness of polyaniline thin films by atomic force microscopy

Polyaniline (PANI) thin films with different thicknesses have been deposited on indium tin oxide (ITO) coated glass substrates by electrochemical polymerization of the aniline monomer in H2SO4 aqueous solution. By using the tip of an atomic force microscopy (AFM) apparatus as an indenter, cantilever deflection versus sample vertical displacement curves have been acquired and analyzed for evaluating the contact stiffness, by using an approach analogous to that developed for standard depth sensing indentation (DSI) tests. After the calibration performed using a set of polymeric reference materials, indentation modulus and hardness of PANI films have been deduced as a function of the reached maximum penetration depth. By using a model originally proposed for the analysis of standard DSI measurements, indentation modulus and hardness values of only PANI are finally deduced from the corresponding apparent values measured for the film-substrate systems, although they have to be considered as semi-quantitative estimations, since the roughness of the films does not allow a certain determination of the local thickness in correspondence of the probed points.

Monolithic Carbon-based Nanocomposites with Hierarchical Porosity: Novel Anode Materials for Li Ion Batteries

This study compares the effects of meso- and macroporosity and the influence of nanocomposite structure on textural, electronic, and mechanical properties of monolithic carbon samples. Glassy carbon monoliths with three-dimensionally ordered macropores and walls containing mesopores (3DOM/m C) were synthesized by nanocasting from monolithic silica with hierarchical pore structure. Subsequent introduction of more graphitic, nitrogen-doped carbon into the mesopores by chemical vapor deposition produced a monolithic 3DOM/m carbon-graphitic carbon nanocomposite material (3DOM/m C/C). The materials were characterized in detail by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen- adsorption measurements, depth-sensing indentation, and electrochemical measurements.

Magnetron sputtered Ti–Si–C thin films prepared at low temperatures

In this work, low temperature Ti–Si–C films were deposited onto silicon and polished stainless steel and high-speed steel substrates by DC magnetron co-sputtering from two Ti targets, one with C pellets and the other with Si pellets. The composition of the films was investigated by Electron Probe Micro-Analysis (EPMA), while structure was characterized using a conventional X-ray diffractometer. The hardness and residual stress were studied using depth-sensing indentation and substrate deflection measurements (using Stoney's equation), respectively. Plots of both C/Ti and Si/Ti atomic ratios as a function of the targets current ratio showed the existence of two distinct regions: (i) a silicon rich zone (target current ratios, I Ti–C/ I Ti–Si, up to 0.5, Si/Ti atomic ratios in the range of 0.21–0.27 and low C/Ti atomic ratio, < 0.17), and (ii) a carbon rich zone (films were prepared with target current ratios, I Ti–C/ I Ti–Si, between 1.4 and 2.9, with C/Ti atomic ratio in the range of 0.29–0.34 and low Si/Ti atomic ratio). These two composition regions were found to be of particular influence in all scanned properties. Structural analysis revealed the possibility of the coexistence of different phases in the prepared films, namely a sub-stoichiometric fcc NaCl-type TiC structure and a Ti metallic phase (α-Ti or β-Ti). The coatings with highest carbon content (carbon rich zone), exhibit mainly a sub-stoichiometric fcc NaCl TiC-type structure. The films within the silicon rich zone show a progressive tendency for amorphization. The existence of some C or even Si(C) amorphous tissues cannot be excluded. The residual stress states ( σ r) and the hardness values ( H) were relatively low, σ r < − 1 GPa and H = 7–11 GPa, respectively, which could be a consequence of the low crystallinity order exhibited by the coatings and/or due to the high amounts of Ti in the coatings.

Determination of fatigue mesoscopic mechanical properties of an austenitic stainless steel using depth-sensing indentation (DSI) technique

In this paper, the depth-sensing indentation (DSI) technique was used to investigate the mechanical properties at the mesoscopic scale of 18Cr–8Ni austenitic stainless steel subjected to low-cycle fatigue loading. For this purpose, several representative analytical approaches for extracting basic mechanical properties, such as the indentation hardness ( H), Young's modulus ( E), yield strength ( σ ys), strain hardening exponent ( n) and plastic energy ( W p), from the indentation load–depth ( P– h) curve were introduced. A series of experiments including constant amplitude low-cycle fatigue tests, DSI measurements and transmission electron microscopy (TEM) observations were carried out to obtain the change characteristics of the mechanical properties at the mesoscopic scale of the material as well as their micromechanisms. It is shown that, for the polycrystalline metal investigated, the cyclic plastic deformation remarkably influences its subsequent elastic–plastic response of the small volume material to the indentation process. As the strain amplitudes increases, the mesoscopic mechanical properties ( H, E, σ ys, and n) show increase, while the plastic energy of the indentation ( W p) exhibits a decrease process. Microstructure observations using TEM reveal that, with increasing strain amplitudes, the dislocation substructures in the material tend towards cell formation and the size of dislocation cells tend to progressively decrease. The dependence of the microstructures on the applied strain amplitude is thus responsible for the change characteristics of the mechanical properties at the mesoscopic scale of the material subjected to low-cycle fatigue loading.

Effects of Hierarchical Architecture on Electronic and Mechanical Properties of Nanocast Monolithic Porous Carbons and Carbon−Carbon Nanocomposites

This study compares the effects of meso- and macroporosity and the influence of nanocomposite structure on textural, electronic, and mechanical properties of monolithic carbon samples. Glassy carbon monoliths with three-dimensionally ordered macropores and walls containing mesopores (3DOM/m C) were synthesized by nanocasting from monolithic silica with hierarchical pore structure. The porous silica monoliths (3DOM/m SiO2) were prepared by combining colloidal crystal templating with surfactant templating. These preforms were infiltrated with a phenolic resin through a gas-phase process. After carbonization and HF extraction of silica, the resulting carbon monoliths maintained the open, interconnected macropore structure of the preform and the mesoporosity of the skeleton, which provided a high surface area >1200 m2/g to the material. Subsequent introduction of more graphitic, nitrogen-doped carbon into the mesopores by chemical vapor deposition produced a monolithic nanocomposite material (3DOM/m C/C). The materials were characterized in detail by powder X-ray diffraction, Raman spectroscopy, small-angle X-ray scattering, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, nitrogen-adsorption measurements, depth-sensing indentation, and electrochemical measurements. The mechanical strength, electronic conductivity, and capacity for lithiation of 3DOM/m C, 3DOM/m C/C, and a 3DOM carbon prepared from resorcinol-formaldehyde precursors without templated mesopores (3DOM RFC) were compared to evaluate the effects of the wall nanostructure and composition on these properties. The mechanical strength and electronic conductivity of the nanocomposite were significantly higher than those before addition of the second carbon phase. The nanocomposite suppressed formation of a solid-electrolyte interface layer during lithiation and had higher lithiation capacity than 3DOM RFC at high discharge rates, but not at low rates.