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In this work, the mechanical properties of hydride diffusion layer were thoroughly researched by nanoindentation technique. For the first time, the clear section microstructure of hydride diffusion layer was revealed under scanning electron microscope with complicated interactions of hydride plates near the interface between hydride layer and titanium matrix. The hydride layer section has higher hardness and lower modulus towards titanium matrix due to the hard nature and easier crack nucleation of hydride precipitation. Besides, the hardness of titanium matrix shows considerable anisotropy. The anisotropic hardness of sample surface was studied before and after hydrogen charging. The hardness of titanium matrix decreases with the increase of deviation angle between c -axis and surface normal. The hydride layer formed in the titanium grain with more favorable orientation for hydride transformation tends to possess higher indentation hardness. [ABSTRACT FROM AUTHOR]

In this work, the mechanical properties of hydride diffusion layer were thoroughly researched by nanoindentation technique. For the first time, the clear section microstructure of hydride diffusion layer was revealed under scanning electron microscope with complicated interactions of hydride plates near the interface between hydride layer and titanium matrix. The hydride layer section has higher hardness and lower modulus towards titanium matrix due to the hard nature and easier crack nucleation of hydride precipitation. Besides, the hardness of titanium matrix shows considerable anisotropy. The anisotropic hardness of sample surface was studied before and after hydrogen charging. The hardness of titanium matrix decreases with the increase of deviation angle between c -axis and surface normal. The hydride layer formed in the titanium grain with more favorable orientation for hydride transformation tends to possess higher indentation hardness. [ABSTRACT FROM AUTHOR]

Abstract: The accuracy of measurement of mechanical properties of a material using instrumented nanoindentation at extremely small penetration depths heavily relies on the determination of the contact area of the indenter. Our experiments have demonstrated that the conventional area function could lead to a significant error when the contact depth was below 40nm, due to the singularity in the first derivation of the function in this region and thus, the resultant unreasonable sharp peak on the function curve. In this paper, we proposed a new area function that was used to calculate the contact area for the indentations where the contact depths varied from 10 to 40nm. The experimental results have shown that the new area function has produced better results than the conventional function. [Copyright &y& Elsevier]

Abstract: In the present work, Lemaitre''s damage assessment methodology has been applied to predict evolution of damage during tensile test at ambient temperature and at 823K in nickel based IN 718 super alloy. The damage has been evaluated through apparent elastic modulus measurement from each unloading step during the test. Marked difference was found in damage evolution and operative damage micromechanisms at these test temperatures. Critical points have been identified on the damage evolution curves for room temperature loading condition. Based on these parameters, the damage has been predicted using Lemaitre''s damage model for high temperature specimen. The damage predicted is found to be in good agreement with experimental curve. [Copyright &y& Elsevier]

Abstract: Lead-free eutectic SnBi and SnAgCu solder alloys were studied by nanoindenter. Eutectic SnPb solder was also examined for comparative purpose. Their mechanical properties including hardness, reduced modulus and creep rate sensitivity coefficient m values were obtained. It was found that eutectic SnAgCu solder is stiffer than both eutectic SnBi solder and SnPb solder, while eutectic SnBi is the hardest among these solder alloys. For eutectic SnAgCu alloy, its m value obtained by nanoindenter was in excellent agreement with that by uniaxial tensile test. Both lead-free solders showed more creep resistance than eutectic SnPb solder. Nanoindenter is a useful way to characterize the small sized materials of electronic components. [Copyright &y& Elsevier]

Abstract: The problem of accurate identification of mechanical properties, primarily hardness and modulus, invariably arises whenever very thin coatings are considered that consist of single or multiple layers, e.g. in the context of fitness-for-purpose characterisation of coated systems, monitoring in-service degradation, component lifetime prediction, etc. Rapid developments in the areas of nano-fabrication, nano-manipulation and nano-technology lead to the increased importance of reliable characterisation of mechanical properties of progressively thinner coatings. Instrumented small scale (nano-) indentation is particularly well-suited to surface-engineered and thin-coated systems. The present study presents a review and refinement of the interpretation techniques for instrumented (nano) indentation for reliable property de-convolution of coated systems. Particular attention is devoted to contact modulus and hardness, as the properties that play the key role in controlling the deformation response of any surface, and affect such service properties as impact and erosion resistance, wear and fretting fatigue resistance, resistance to crack initiation and propagation, etc. A flexible multi-scaling power law functional description is introduced and discussed, and its application to various example systems is illustrated. [Copyright &y& Elsevier]

Abstract: Thermal spray coatings exhibit a wide variety of hierarchial and multiscale microstructural characteristics that lead to variation in their functional properties and performance. The array of defect structures, orthotropic behaviour and process-induced attributes (e.g. quenching stresses) all add to complexity in understanding and predicting their performance. A complete understanding of the plasma spray process includes examination of the particle–jet interaction, particle impact (to form the splats) and the particle–substrate interaction during coating deposition. This link has been established by using diagnostic tools in conjunction with a splat collection shutter and an ‘in situ’ curvature measurement instrument. In this study, commercial grade spherical molybdenum (Mo) powder was plasma sprayed and the spray stream was characterized for resulting particle state. A ‘splat map’ was deposited through a ‘spray stream guillotine’ to capture the fingerprint of the plume cross-section. Subsequently, coatings were deposited at these spray conditions on a newly developed ‘in situ’ curvature measurement instrument to measure coating residual stresses and to estimate the coating modulus. Splats and coatings were subsequently characterized by microdiffraction (for splat residual stresses), nano and microindentation for elastic and elastic–plastic properties and by electron microscopy. This complete history of the process followed by splat and coating characterization provides insight into the correlation between processing parameters, resultant particle states and final coating properties. The role of particle temperature and velocity on the splat (and coating) morphology and residual stress is explained in the results. [Copyright &y& Elsevier]

Combustion chemical vapor deposition (combustion CVD) was used to deposit thin films of yttria stabilized zirconia (YSZ) and alumina (Al2O3). Nanoindentation analysis for hardness, modulus and fracture toughness of the films as well as several bulk materials, including single crystal Al2O3, MgO, SiO2, YSZ and polycrystalline Al2O3 was conducted. YSZ films that were produced with a total cation molarity of 0.005 M possessed significant surface roughness that was not conducive to nanoindentation measurements. The lower concentration investigated, 0.002 M provided a repeatable deposition condition that produced thin films with consistent hardness and modulus values. Load-displacement measurements at very low loads (up to total displacements of 200 nm) showed that the Al2O3 films tended to plastically deform, whereas the YSZ films showed less of a tendency to do so. For Al2O3 films that were 0.38±0.09 μm thick, the modulus, hardness and fracture toughness values were 28.6±1.6 GPa, 479±15 GPa and 2.22±0.31 MPa m0.5, respectively; for YSZ films that were 0.65±0.05 μm thick, the values were 16.1±4.6 GPa, 388±89 GPa and 1.67±0.46 MPa m0.5, respectively. These values were found to be consistent with the values measured via nanoindentation in this work for bulk samples of Al2O3 and YSZ, as well as to those reported in the literature. [Copyright &y& Elsevier]

Nano-indentation experiments on various sintered bioceramic powders and bioceramic functionally graded coatings, were performed with a berkovich indenter to establish an improved method for determining hardness and elastic modulus from load and displacement data. The materials included, spherical hydroxyapatite, SHA (Taihei chemicals, Japan), hydroxyapatite powders of different batches namely, P81B, P88 and P120 (Plasma Biotal, UK), in-house hydroxyapatite, HA and alpha tri-calcium phosphate, αTCP (Merck, Germany), functionally graded coatings (FGC''s) of HA–G–Ti and HA–αTCP–Ti. The elastic modulus and hardness values of all the materials were obtained by nano-indentation with the corresponding load–displacement curves confirming the characteristic properties of the sintered materials and functionally graded coatings. The results showed that the SHA powder yielded the highest modulus and hardness value and P88 (HA) showed the least value confirming that its relatively softer than other bioactive powders. Furthermore, the continuous stiffness measurement also showed that SHA yielded the best mechanical property. In case of the FGC''s, HA–G–Ti yielded higher values of modulus and hardness in comparison with HA–αTCP–Ti. [Copyright &y& Elsevier]

In this study, the cyclic response of the wrought magnesium alloy ZM21 is investigated. The microstructure of the original extruded bar consists of equiaxed grains with a grain size range of 15–18 μm. The anelasticity was measured using a method in which the elastic modulus in every loop is obtained by calculating the slope of lines fitted to the loading and unloading parts of the curves. The cyclic test for ZM21 shows that the anelastic strain increases with the strain, reaching its maximum between 2-4% applied strain and then levels off. The anelastic strain reaches a maximum between 2-4% at which point the fraction of extension twins also reaches a maximum. Twins were separated from their parent grains in order to quantify twin evolution during cyclic loading. Overall, it was found that most of the twins observed are extension twins up to 8% accumulative strain. Beyond 8% strain, exhaustion of 90% of extension twins occurred and contraction twins appeared in the microstructure. Moreover, double twins were identified after a strain of 8%. These twins were composed of extension twins and contraction twins which can contribute to softening. Such softening can result in the reduction of uniform elongation in tension for the cyclic loading in comparison with the monotonic loading. It was possible for the material to sustain continued straining without failure to over double this value, that is, 15%. [ABSTRACT FROM AUTHOR]