bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elastic modulus of dental enamel: effect of enamel prism orientation and mineral content
Authors: Ferguson V. L. , Boyde Alan , Bushby Andrew J. 
Published: April 2011

ABSTRACTNanomechanical properties of mineralized tissues are determined by microstructural tissue organization and relative composition of organic, mineral, and water phases. We combine nanoindentation and quantitative backscattered electron (qBSE) imaging to understand how these factors influence material properties at the ultrastructural and tissue level. Developmental stages of equine tooth enamel provide a good situation for studying the effects of enamel prism orientation and mineralization. Equine cheek teeth continue to form new enamel whilst mature tissue is being worn away. Hence we can study graded mineral content that increases with enamel maturity. Hunter-Schreger bands (HSBs) containing enamel prisms of contrasting orientations allow investigation of the effect of orientation on modulus. An equine second mandibular molar (2-year-old) was embedded in poly-methylmethacrylate, sectioned longitudinally, polished, carbon coated, imaged in qBSE, and subjected to nanoindentation testing. Elastic modulus increases significantly during maturation as enamel protein matrix degradation makes space for increased mineral content with closer proximity of enamel crystals, finally reaching values exceeding 80 GPa for little further increase in mineral content. Indentations spanning HSBs in immature, poorly mineralized enamel yielded modulus values that varied with prism orientation in a sinusoidal pattern where modulus varies by as much as a factor of three. Nanoindentation helps to elucidate how the composition and ultrastructural organization of enamel contribute to mechanical properties.
Effects of Osteopontin Deficiency and Aging on Nanomechanics of Mouse Bone
Authors: Kavukcuoglu B. , West C. , Denhardt D. T. , Mann A. B. 
Published: April 2011

ABSTRACTOsteopontin (OPN), a phosphorylated glycoprotein, is among the most abundant non-collageneous bone matrix proteins produced by osteoblasts and osteoclasts. OPN has been implicated in bone formation, resorption and remodeling. However, previous studies have presented contradictory results regarding the effect of OPN on the mechanics and microstructure of bone. This study has used nanoindentation to identify local variations in elastic modulus and hardness of OPN deficient (OPN -/-) and wild-type control (OPN+/+) mouse bones. Specifically, the study has looked at changes in the mechanical properties of OPN-/- and OPN+/+ mouse bones with the mouse's age. Cortical sections of femurs from different age groups ranging from 3 weeks to 58 weeks were tested and compared. The results suggest that there are large, abrupt variations in mechanical properties across the femur's radial section for 3-week-old mouse bone. The hardness (H) drops significantly towards the inner and outer sections so the cortical bone has a mean H=3.66 GPa with a standard deviation of 2.44 GPa. In contrast, the hardness of the 58-week-old mouse bone had a standard deviation of 0.35 GPa and a mean H=1.45 GPa. The hardness across the radial axis of the 58-week-old bone was found to be quite uniform. The elastic modulus showed similar variations to the hardness with respect to age and position on the bone. We conclude that the mechanical properties of the mouse bones decrease substantially with maturity, and statistically the hardness and elastic modulus are more uniform in mature bones than young ones. Surprisingly we found a similar variation in both OPN-/- and OPN+/+ bones, with no statistically significant difference in the mechanical properties of the OPN -/- and OPN+/+ bones. The results for OPN-/- and OPN+/+ mouse bones are particularly important as control of OPN activity has been postulated as a potential treatment for bone pathologies that exhibit a change in the bone mineralization, such as osteoporosis, osteopetrosis and Paget's disease. Understanding the effects of OPN on bone mechanics is a vital step in the development of these new treatments.
High Temperature Deformation of AlN/CrN Multilayers using Nanoindentation
Authors: Giuliani F. , Goruppa A. , Lloyd S. J. , Teer D. , Clegg W. J. 
Published: April 2011

ABSTRACTThe aim of this paper is to investigate the deformation behaviour of an AlN/CrN multilayer with wavelengths varying from 6–400 nm, deposited on M42 tool steel and how this varies as the temperature is increased to 500 °C. These measurements have been correlated with changes in deformation patterns using cross-sectional transmission electron microscopy, where sections have been prepared directly through the indents.
Mechanical Properties of Wear Tested LIGA Nickel
Authors: Moody N. R. , Jungk J. M. , Kennedy M. S. , Prasad S. V. , Bahr D. F. , Gerberich W. W. 
Published: April 2011

ABSTRACTStrength, friction, and wear are dominant factors in the performance and reliability of materials and devices fabricated using nickel based LIGA and silicon based MEMS technologies. However, the effects of frictional contacts and wear on the mechanical performance of microdevices are not well-defined. To address these effects on performance of LIGA nickel, we have begun a program employing nanoscratch and nanoindentation. Nanoscratch techniques were used to generate wear patterns using loads of 100, 200, 500, and 990 μN with each load applied for 1, 2, 5, and 10 passes. Nanoindentation was then used to measure properties in each wear pattern correcting for surface roughness. The results showed a systematic increase in hardness with applied load and number of nanoscratch passes. The results also showed that the work hardening coefficient determined from indentation tests within wear patterns follows the work hardening behavior established from tensile tests, supporting use of a nanomechanics-based approach for studying mechanical properties of wear tested material.
TEM Observation of Microstructural Change of Silicon Single Crystal Caused by Scratching Tests Using SPM
Authors: Takagi M. , Onodera K. , Iwata H. , Imura T. , Sasaki K. , Saka H. 
Published: April 2011

ABSTRACTIn this study, the microstructural change of the surface of Si single crystal (Si(100)) after the scratching tests under very small loading forces was investigated. At first, line-scratching tests and scanning-scratching tests were carried out using an atomic force/friction force microscope (AFM/FFM). Next, cross-sectional TEM observations of the wear marks which were generated by the scratching tests were carried out. As a result of the TEM observations after the line-scratching tests, it was found that dislocations were observed in the area of less than 100nm thickness from the surface of the wear marks which were formed under the loading forces of more than 5μN. In the case of the loading forces of more than 20μN, an amorphous region was also observed just under the wear marks. As a result of the TEM observations after the scanning-scratching tests, it was found that the introduction of dislocations took place and no amorphous region appeared. It was also found that the several atomic layers at the top surface of the wear marks shifted in parallel to (100).
Fracture mechanisms of GaAs under nanoscratching
Authors: Solletti J.-M. , Parlinska-Wojtan M. , Tharian J. , Wasmer K. , Michler J. , Ballif C. , Schulz D. , Karimi A. 
Published: April 2011

ABSTRACTNanoscratching on GaAs (001) by a pyramidal diamond tip (Berkovitch) indenter has been carried on under different loads, scratching velocities and directions. Plastic deformation and fractures induced by scratching have been investigated by atomic force microscopy (AFM), and by scanning and transmission electron microscopy (SEM and TEM, respectively). Surface images revealed radial and surface tensile cracks. Focused ion beam (FIB) milling of the contact area revealed median and shear fracture distribution in the volume. The different cracks were characterized for various scratching conditions in terms of their direction of propagation, extension and frequencies. Plastic deformations have been characterized by vertical displacement of material. No purely ductile zone was observed, GaAs deformation occurred by fractures and plastic strain. Their preponderances are discussed in terms of material properties.
Microstructures and Mechanical Properties of NiAl-Mo Composites
Authors: Bei H. , George E. P. 
Published: April 2011

ABSTRACTIn-situ composites consisting of ∼14 vol.% continuous Mo fibers embedded in a NiAl matrix were produced by directional solidification in a xenon-arc-lamp, floating-zone furnace. The fiber spacing and size were controlled in the range 1–2 μm and 400–800 nm, respectively, by varying the growth rate between 80 and 20 mm/h. Electron back-scatter diffraction patterns from the constituent phases revealed that the growth directions and interface boundaries exhibited the following orientation relationships: 〈l00〉NiAl//〈100〉Mo and {011}NiAl//{011}Mo. The temperature dependence of the tensile strength and ductility were investigated and the NiAl-Mo composite was found to be both stronger and have a lower ductile-brittle transition temperature than the unreinforced NiAl matrix.
The Effects of Substitutional Additions on Tensile Behavior of Nb-Silicide Based Composites
Authors: Cretegny Laurent , Bewlay Bernard P. , Ritter Ann M. , Jackson Melvin R. 
Published: April 2011

ABSTRACTNb-silicide based in-situ composites consist of a ductile Nb-based solid solution with high-strength silicides, and they show excellent promise for aircraft engine applications. The Nb-silicide controls the high-temperature tensile behavior of the composite, and the Nb solid solution controls the low and intermediate temperature capability. The aim of the present study was to understand the effects of substitutional elements on the room temperature tensile behavior and identify the principal microstructural features contributing to strengthening mechanisms.
Factors for Controlling Martensitic Transformation Temperature of TiNi Shape Memory Alloy by Addition of Ternary Elements
Authors: Hosoda Hideki , Wakashima Kenji , Miyazaki Shuichi , Inoue Kanryu 
Published: April 2011

ABSTRACTCorrelations between the changes in martensitic transformation start temperature (Ms) by addition of ternary elements X and several factors of the ternary additions were investigated for TiNi shape memory alloy. The change of Ms by addition of 1mol%X is referred to as ΔMs (in K/mol%), and ΔMs was systematically evaluated by differential scanning calorimetry experimentally using (Ti, X)50Ni50 solution-treated at 1273K for 3.6ks where the Ni content was kept constant to be 50mol%. The ternary additions X investigated are the transition metal (TM) elements selected from 4th period group (Zr, Hf) to 10th period group (Pd, Pt). The factors investigated are (1) the number of total outer d- and s-electrons (Nele), and electron hole number (NV), (2) electronegativity (EN), (3) atomic volume (VX) and (4) Mendeleev number (NM). It was found that the values of ΔMs are different even in a same period group; ΔMs of 6th period group are -133K/mol%Cr (3d-TM), -152K/mol%Mo (4d-TM) and -64K/mol%W (5d-TM) for example. The results found in the correlations between ΔMs and those factors are summarized as follows. (1) ΔMs depends on Nele and NV. However, the data are scattered because same Nele and NV are often given in a same period group. Then, other factors than Nele and NV are required for clear understanding of ΔMs. (2) ΔMs seems to become lowered slightly with increasing EN. (3) ΔMs weakly depends on atomic volume VX. Ternary addition with large VX increases ΔMs slightly, and with small VX decreases ΔMs largely. Since the stress field must be formed by substitution due to size mismatch, the type of stress field, tension/compression, may be an important role to determine the sign of ΔMs. (4) ΔMs shows a good correlation with NM as -9.4Kmol%−1/ΔNM where ΔNM is the difference in NM. This suggests that a ternary alloying element with smaller (larger) NM stabilizes the B19’ martensite (B2 parent) phase. Effect of site occupancy on Ms is also discussed only for Cr.
Advanced TEM Investigations on Ni-Ti Shape Memory Material: Strain and Concentration Gradients Surrounding Ni4Ti3 Precipitates
Authors: Schryvers Dominique , Tirry Wim , Yang Zhiqing 
Published: April 2011

ABSTRACTLattice deformations and concentration gradients surrounding Ni4Ti3 precipitates grown by appropriate annealing in a Ni51Ti49 B2 austenite matrix are determined by a combination of TEM techniques. Quantitative Fourier analysis of HRTEM images reveals a deformed nanoscale region with lattice deformations up to 2% while EELS and EDX indicate a Ni depleted zone up to 150 nm away from the matrix-precipitate interface.
Investigation of the structure and properties of hypereutectic Ti-based bulk alloys
Authors: Louzguine-Luzgin Dmitri V. , Louzguina-Luzgina Larissa V. , Inoue Akihisa 
Published: April 2011

ABSTRACTStructure and mechanical properties of binary Ti-TM (TM-other transition metals) and ternary Ti-Fe-(TM, B or Si) alloys produced in the shape of the arc-melted ingots of about 25 mm diameter and 10 mm height are studied. The formation of high-strength and ductile hypereutectic alloys was achieved in the Ti-Fe, Ti-Fe-Cu and Ti-Fe-B systems. The structures of the high-strength and ductile hypereutectic alloys studied by X-ray diffractometry and scanning electron microscopy were found to consist of the primary cubic Pm3 m intermetallic compound (TiFe-phase or a solid solution on its base) and a dispersed eutectic consisting of this Pm3m intermetallic compound + BCC Im 3 m β-Ti supersaturated solid solution phase. The hypereutectic Ti-Fe alloy showed excellent compressive mechanical properties. The addition of Cu improves its ductility. B addition increased mechanical strength. Ni, Cr and Mn additions caused embrittlement owing to the formation of alternative intermetallic compounds. The deformation behaviour and the fractography of the Ti-based alloys were studied in details. The reasons for the high strength and good ductility of the hypereutectic alloys are discussed.
In-situ Observation of Surface Relief Formation and Disappearance during Order-Disorder Transition of Equi-atomic CuAu alloy using Laser Scanning Confocal Microscopy
Authors: Miura Seiji , Okuno Hiroyuki , Ohkubo Kenji , Mohri Tetsuo 
Published: April 2011

ABSTRACTIn-situ observation of the formation and disappearance of the surface relief associated with the twinning during the order-disorder transitions among CuAu-I (L10), CuAu-II (PAP) and disordered fcc phases was conducted using Confocal Scanning Laser Microscopy equipped with a gold image furnace. The Retro effect was confirmed in poly-crystal samples, however no evidence was found in single-crystal samples. Also observed in poly-crystal samples are that the disordering temperature detected by the disappearing of relieves is different from grain to grain, and that grain boundary cracking alleviates the Retro effect. The observed phenomena were explained based on the crystallographic orientation relationship among grains investigated by FESEM/EBSD in terms of the elastic strain effect around grain boundaries induced by transition. It was confirmed that in each grain the surface relieves correspond to a set of two {011} planes having a <100> axis perpendicular to both planes in common. It was also found that the larger the average strain of two neighboring grains is, the lower the transition temperature. This observation was explained by the stress effect on the stability of a phase.
Optimisation of Precipitation for the Development of Improved Wrought Fe3Al-based Alloys
Authors: Kobayashi Satoru , Zaefferer Stefan , Schneider André 
Published: April 2011

ABSTRACTEffect of TiC precipitates on the kinetics of static recrystallisation has been studied by using a Fe-26Al-5Cr (at%) single-phase (α:A2/B2/D03) alloy and two-phase (α+TiC) alloys with different amounts of TiC precipitates. Based on the results, a desirable thermo-mechanical processing is proposed for the development of wrought Fe3Al-based alloys with strengthening MC carbides.In the alloys with a high amount of TiC, needle-like TiC precipitates with 1–10 μm in length formed during air-cooling after homogenisation. Hot deformations with such large precipitates cause inhomogeneous deformation around the particles, leading to particle stimulated nucleation (PSN) and hence accelerate recrystallisation.The occurrence of PSN is harmful for the embrittlement problem, i.e. ductility drastically decreases when recrystallisation occurs, but useful for grain refinement. The following process is proposed to accomplish grain refinement, strengthening by precipitates and avoidance of the embrittlement: hot deformation with a large amount of precipitates to make grain refinement possible by using PSN, followed by hot deformation with a small amount of precipitates near α single-phase region and a subsequent heat treatment to obtain fine precipitates. The fine particles would also act to pin the boundaries of growing grains, thus leading to extended recovery rather than recrystallisation. This process is difficult to carry out in the (Fe-26Al-5Cr)-TiC system because the temperature necessary to enable precipitation is very high and the kinetics is quick. The precipitation temperature is significantly decreased by replacing TiC by VC or MoC.
Application of the CSL Model to Deformation Twin Boundary in B2 Type TiNi Compound
Authors: Nishida Minoru , Matsuda Mituhiro , Morizono Yasuhiro , Fujimoto Towako , Nakashima Hideharu 
Published: April 2011

ABSTRACTThe deformation structure of B2 type TiNi compound around 573 K has been investigated by transmission electron microscopy (TEM). Serrations are seen in stress-strain curve, which corresponds to the formation of various planar defects with twin relation. The dominant planar defect found in the specimens showing serration is {114} compound twin. The other defects are in mirror symmetry with respect to {113}, {115}, {447} planes and so on. These defects are considered to be <110> symmetric tilt boundaries in bcc structure by ignoring the atomic arrangement of B2 structure and are characterized with Σ value based on coincide site lattice (CSL) model. For instance, the Σ value of {114}, {113}, {115} and {447} boundaries are Σ9, Σ11, Σ27 and Σ81, respectively. Numerous (114) defects initially form at grain boundary and grow into grain interior. Some of those deflect to (-1–14) defects. In such case, the {447} Σ81defect is always observed at the interface of (114) Σ9 and (-1–14) Σ9 defects. This fact indicates that the sigma combination rule of the CSL model can be applied to the triple junction of defects. Similarly, {7710} Σ99 boundary forms at the interface of {114} Σ9 and {113} Σ11 defects. It can be concluded that the ductility of B2 type TiNi compound around 573 K is attributable to the formation of various planar defects with large shear strain and the increment of independent slip system due to the formation of planar defects, and that the arrangement of some planar defects conforms to the sigma combination rule of CSL model.
Effect of Excess Vacancies on Antiphase Domain Growth in Fe3Al
Authors: Koizumi Y. , Hagiwara T. , Minamino Y. , Tsuji N. 
Published: April 2011

ABSTRACTThe growth of the D03-type antiphase domain (APD) in Fe3Al was investigated focusing on the effect of excess vacancies that were introduced during the quenching process from the disordered state. The variation in the APD size exhibited considerable deviation from the conventional “parabolic growth law” in the early stage of APD growth. This variation was numerically calculated on the assumption that the migration of the APD boundaries was enhanced by non-equilibrium excess vacancies and the vacancy concentration decreased during the isothermal annealing for the APD growth. The calculated variations in the APD size could be successfully fitted to the experimental results in cases with quenching temperatures (Tq) of 873 K or 1073 K, but not when Tq was 1273 K. The APD growth in the latter case was much slower than the expected growth derived from the calculation. This discrepancy was attributed to the rapid decrease in the vacancy concentration due to vacancy clustering since a significant amount of dotted contrasts were observed in TEM image of only the specimen quenched from 1273K.
Microstructures in Cold-Rolled Ni3Al Single Crystals
Authors: Kishida Kyosuke , Demura Masahiko , Hirano Toshiyuki 
Published: April 2011

ABSTRACTMicrostructure evolution during cold rolling of binary stoichiometric Ni3Al single crystals was examined by the optical (OM) and transmission electron microscopy (TEM). In the case of the <001> initial RD, the banded structure is formed. Inside each matrix band, the localized shear deformations occur alternately on two {111} planes. In addition, huge amounts of widely extended superlattice intrinsic stacking faults (SISFs) are observed from relatively early stage of cold rolling. The occurrence of the localized shear deformation is considered to be controlled by the SISFs since they must be strong obstacles for the dislocation motion on the other glide plane. The extensive formation of the SISFs is therefore considered to be one of the most important microstructural features which control the cold rolling behavior of Ni3Al.
High-Temperature Environmental Embrittlement of Thermomechanically Processed TiAl-Based Intermetallic Alloys with Various Kinds of Microstructures
Authors: Takasugi T. , Hotta Y. , Shibuya S. , Kaneno Y. , Inoue H. , Tetsui T. 
Published: April 2011

ABSTRACTThermomechanically processed TiAl-based intermetallic alloys with various alloy compositions and microstructures were tensile tested in various environmental media including air, water vapor and a mixture gas of 5vol.%H2+Ar as a function of temperature. All the TiAl-based intermetallic alloys showed reduced tensile fracture stress (or elongation) in air, water vapor and a mixture gas of 5vol.%H2+Ar not only at ambient temperature (RT∼600K) but also at high temperature mostly from 600K to 1000K (sometimes higher temperature than 1000K). The high-temperature environmental embrittlement of TiAl-based intermetallic alloy depended upon the microstructure. The possible species causing the high-temperature environmental embrittlement are hydrogen atoms decomposed from water vapor (H2O) or hydrogen gas (H2), similar to those causing the low-temperature environmental embrittlement.
Crystal Structure and Thermoelectric Properties of Al-containing Re Silicides
Authors: Terada Eiji , Oh Min-Wook , Wee Dang-Moon , Inui Haruyuki 
Published: April 2011

ABSTRACTThe microstructure, defect structure and thermoelectric properties of Al-containing ReSi1.75 based silicides have been investigated. All the Al-containing alloys investigated contain four differently oriented domains accompanied by the twinned microstructure, as the binary alloy does. However, thin defect layers containing a kind of shear structure are locally and sporadically formed at some of twin boundaries. In the defect layer, shear occurs by the vector of [100] on either (1 09) or (107) planes. Binary ReSi1.75 exhibits nice thermoelectric properties as exemplified by the high value of dimensionless figure of merit (ZT) of 0.70 at 800 °C when measured along [001], although the ZT value along [100] is just moderately high. Al-containing Re silicides considerably increase the ZT value along [100] so that the maximum value of 0.95 is achieved at 150 °C for the ReSi1.75Al0.02 alloy. The temperature dependence of electrical resistivity changes from of semiconductor for the binary alloy to of metal for the Al-added alloys and the value of electrical resistivity is significantly reduced when compared to the binary counterpart.