This paper presents the effect of neutron irradiation (9.8 × 1024 n/m2 at 438 °C) on the mechanical properties in V-20 wt.% Ti alloys undoped and doped with P using a small punch testing method. The same amount of neutron irradiation-induced hardening, that is almost temperature independent, was observed in undoped and P doped alloys. Neutron irradiation facilitated heterogeneous formation of grain boundary microcracks, not leading to specimen failure, in the undoped alloy. An irradiated undoped alloy showed ductility loss, that is not as much as expected from the easy microcrack formation due to a mixed mode of intergranular and transgranular cracking. Conversely, in the P doped alloy, intergranular microcracking was suppressed and low temperature ductility was improved by the irradiation. The intergranular fracture behavior controlling the ductility change is discussed in terms of the grain boundary composition and yield strength affected by the neutron irradiation.

In a kinetic model [1] for the phenomenon of dynamic embrittlement, the cracking rate is predicted to be proportional to the diffusivity of the embrittling species along the grain boundary. To test this model, bicrystals of Cu-Sn and Fe-Si with Σ5 symmetrical tilt boundaries are used in which tin and sulfur, respectively, are the embrittling elements. The diffusivities parallel and perpendicular to the tilt axis are expected to be different, therefore the crack growth rates in these two directions should vary in the same ratio as the diffusivities.

Preliminary measurements of crack growth rate along the [100] direction in the Cu-Sn alloy bicrystal are presented. The cracking occurred by decohesion along the grain boundary with almost no observable plasticity. The steady state crack growth was found to be approximately 10∼6 m/sec.

The boundary between two perfectly bonded single crystals plays a very important role in determining the deformation of the bicrystal. This work addresses the role of the grain boundary by considering the elevated hardening of a slip system due to a slip gradient. The slip gradients are associated with geometrically necessary dislocations and their effects become pronounced when a representative length scale of the deformation field is comparable to the dominant microstructural length scale of a material. A new rate-dependent crystal plasticity theory is presented and has been implemented within the finite element method framework. A planar bicrystal under uniform in-plane loading is studied using the new crystal theory. The strain is found to be continuous but non-uniform within a boundary layer around the interface. The lattice rotation is also non-uniform within the boundary layer. The width of the layer is determined by the misorientation of the grains, the hardening behavior of slip systems, and most importantly by the characteristic material length scales. The overall yield strength of the bicrystal is also obtained. A significant grain-size dependence of the yield strength, the Hall-Petch effect, is predicted.

Computer simulations of the phenomenon of grain rotation in polycrystalline <111> textured films have been carried out. These simulations provide insight into the evolution of film microstructure due to grain rotation. It is found that grain rotation diminishes with annealing time and stops almost completely when a metastable equilibrium is obtained. The incidence of Σ1, Σ7 and Σ3 Coincident Site Lattice (CSL) boundaries increases with time while the other CSLs reduce in number. Sequential annealing experiments have been performed on thin films of gold. Grain rotation is found to take place with an average rotation rate of about 4°/hour at both 250°C and 350°C.

The experimental technique of electromechanical pull-out testing is introduced to study the interface between fiber and matrix. The technique involves measuring both the contact electrical resistivity and the shear bond strength of a fiber-matrix interface. Samples that are identically prepared differ in contact resistivity and bond strength, which correlate. The correlation allows determination of even small differences in bond strength due to differences in sample preparation conditions. It also gives information on the structure of the interface and allows the bond strength to be nondestructively determined by measuring the contact resistivity. The technique is demonstrated for the interface between steel fiber and cement.

The use of the atomic force microscope (AFM) to measure surface forces has been developed to optimize its operation as a surface imaging tool. This capability can potentially be extended to evaluate nanoscale material response to indentation. In this paper, a novel technique is used to probe local property changes in multi-component polymer systems. Changes in indentation response in interphase regions are investigated for an adhesive system involving a diffuse polymer-polymer bond and for two composite systems. To date, diamond-tipped probes with effective spring constants of 150 and 310 N/m have been used to investigate polyimide and epoxy resin matrices reinforced by carbon fibers.

Physical meaning of thermodynamic parameters of segregation obtained from measurements of chemical composition of grain boundaries in poly crystals and bi crystals, and calculated for individual grain boundary sites is discussed. It is shown that the mean values of these parameters determined from the measurements on polycrystals can in exceptional cases represent the behavior of general grain boundaries. On the other hand, measurements of grain boundary segregation at individual grain boundaries can provide the values of segregation enthalpies and entropies representing behavior of a specific single grain boundary site. The latter data are appropriate for the use in the grain boundary design concept.

An ultra high vacuum (UHV) deposition/bonding system has been constructed that can produce planar interfaces from a wide array of materials. The interfaces in this system can be synthesized in-situ by UHV diffusion bonding of two substrates with or without various interfacial layers. Substrate surfaces can be heat treated, sputter cleaned and characterized in-situ prior to deposition and/or bonding. Interfacial layers can be deposited by e-beam evaporation and/or sputter deposition in any layered or alloyed combination. After deposition, the two substrates are bonded in UHV, by the application of heat and pressure.

This synthesis procedure permits systematic variation and control of interface morphology and chemistry. Integrity of the bonded interface as well as the microstructure and chemistry are examined by cross-sectional analytical transmission electron microscopy. In this study, stainless steel and single and polycrystalline alumina were used as substrate materials to produce interfaces with and without Ti and Cu interlayers.

The effects of Mo contamination on the microstructure of lamp-grade tungsten wire are investigated in this study. Mo is often used as the mandrel material in the coiling of lamp filaments, and when utilized during high temperature heat treatments significant amounts of Mo can diffuse into the W. In this study, W-Mo diffusion couples were prepared and heat treated at temperatures of 2500°C and above to intentionally contaminate the W with Mo. After dissolution of the Mo and additional high temperature heat treatments of the W, equiaxed grains were observed in the W and excessive porosity was also observed. Explanations for these microstructural changes are discussed. Microprobe data were also obtained to quantify interdiffusion between the W and Mo.

Zinc oxide (ZnO) single crystals are grown by the traditional chemical vapor reaction method and ZnO crystal pairs with a single boundary are successfully obtained. The obtained specimens with one ZnO–ZnO boundary (ZnO homojunction) show nonlinear current-voltage (I–V) characteristics without the addition of Bi2O3, CoO, MnO2, and/or rare earth metal oxides. A specimen with higher breakdown voltage shows superior nonlinearity with negative resistivity in its I–V characteristics. Electrical characterization of the ZnO homojunction is conducted and extremely slow response with the current (or voltage) stress is confirmed. The phenomenon had never been observed in commercial ZnO varistors. The surface temperature of the ZnO homojunction is enhanced by larger applied current. The effect of the Joule heat on the nonlinearity in the I–V curves of the ZnO homojunction is discussed.

It has been reported that Ti reduces Al2O3 forming Ti3Al at the interface. From the viewpoint that the structural change of the Ti3Al phase influences the metal-ceramic joining strength, the Ti3Al formation process was analyzed by XPS, XRD, TEM and RBS. Titanium films were deposited on the (1102) surface of Al2O3 substrates and annealed. XRD analysis shows that Ti3Al formation starts at 1073 K. Initially, the (1120) and (2020) Ti3Al planes are oriented parallel to the surface. After 1173 K-300 s heat treatment, XRD shows only the (2020) Ti3Al peak; After 1173 K-600 s heat treatment, HREM observation shows that the lattices of the Ti3Al (0220) plane match those of the A12O3 (1210) plane at the interface. It is suggested that the (2020) oriented grains grow preferentially on the (1102) Al2O3 plane.

The quantity of formed Al increases with heating time. After 420 s, the rate of Al formation falls off. The rate of the Al2O3 reduction is in good agreement with the slightly modified Johnson-Mehl equation. The Ti2O/Ti3Al(O)/Al2O3 layer sequence and morphology can be explained by the pure Ti decrease.

Acoustic emission (AE) events were recorded during the peeling of pressure-sensitive adhesive (PSA) tape from a silicate glass surface. The distributions of AE event durations and energies are found to have the form of power laws. Power-law dependencies (hyperbolic distributions) are recognized as a consequence of self-organized criticality (SOC), resulting from the absence of any characteristic length or time scales. In these studies, standard optical microscopy was used to characterize the fractal nature of the PSA-glass interface. The present results suggest that it is the inherent static structural features found at the fractal PSA-glass interface which produce the observed hyperbolic distributions in AE events, rather than a true SOC process.

Bonding characteristics and interfacial microstructures in explosively welded Ti/stainless steel clad of the as-welded and annealed states were investigated. In case of Ti/SUS430 ferritic stainless steel combination, the average shear strength of an as-welded clad was 555 MPa, and metastable phases such as amorphous and fine crystalline phases were observed at the interface. These were considered to be the trace of melting and subsequently rapid solidification at the contact surface of both the parent materials. By annealing below 1173 K, the strength gradually decreased with increasing holding time. The average shear strength of the clad annealed at 1073 K for 360 ks was 242 MPa, while that of the clad annealed at 1273 K abruptly decreased down to 107 MPa with increasing holding time up to 360 ks. The reaction layer formed at the interface consisted only of TiC in the former. On the other hand, the coexistence of TiC, TiFe, TiFe2 and χ was observed at the interface in the latter. The TiC in the former was considered to serve as a barrier for diffusion of Ti, Fe and Cr across the interface and to suppress the formation of intermetallic compounds. As a result, the growth of reaction layer was inhibited and high bonding strength was preserved even after prolonged annealing. The results of the Combination of Ti and SUS304 austenitic stainless steel were also discussed.

The magnetic properties of sputtered RE-TM(CoGd)/Pd multilayered films were studied. CoGd layers with high Gd concentration were amorphous. Reducing the Gd concentration, CoGd layers changed from amorphous to crystalline gradually. Like in the crystalline Co/Pd multilayered films, perpendicular magnetic anisotropy(PMA) was observed only for CoGd/Pd multilayered films with thin magnetic layer. It is interesting to note that critical magnetic layer thickness, below which the easy magnetization axis is perpendicular to the film plane, reaches 2.5nm for CoGd/Pd multilayered films with amorphous CoGd layers and is larger than that of Co/Pd multilayered films. Kerr rotation was found decreased with the adding of Gd.

Polycrystalline TiN/ZrN multilayers with a 7.5% lattice mismatch between the layers and TiN/CrN multilayers with a 2.3% mismatch were grown by reactive magnetron sputtering on WC/Co sintered hard alloy substrates. Multilayer structure and composition modulation amplitudes were studied using x-ray diffraction method. Hardness and elastic modulus were measured by nanoindentation testing. Hardness of TiN/ZrN multilayers decreased rapidly with increasing bilayer thickness (Λ), peaking at hardness values ≈30% lower than rul e-of-mixtures values at Λ=30 Å, before increasing slightly with further increases in Λ. A comparison with other lattice mismatched systems, TiN/VN and TiN/NbN, showed a similar hardness variation, but a sign was negative. The results suggest that coherency strains were responsible for the larger hardness change. Nanoindenter elastic modulus results showed the same behavior with hardness dependence, i.e., elastic softening at Λ=30 Å. The results of TiN/CrN systems showed no hardness and elastic anomalies within boundaries corresponding to individual values. It was thought too large the difference between hardness (or modulus) of TiN and CrN.

TiN, ZrN, and CrN films were grown by reactive magnetron sputtering on WC-Co sintered hard alloy substrates. Hardness and elastic modulus were measured by nano-indentation tester with low load on tip at 200 mgf. Hardness values were shown the higher value the thinner film thickness due to stress in the films.

Surface properties of BaTiO3 which contain different Ba/Ti ratios were examined by FTIR spectroscopy. Most of the carbonates on the surfaces of these powders were removed by heat treatment at 1200°C. However, it was more difficult to remove the carbonates from the powder with a higher ratio of Ba/Ti. Analysis of the heat treated, aged powders in humid air showed that the barium-excess powder recovered carbonates within several hours. In contrast, titanium-excess powders took a longer time, indicating that barium ion concentration is a reaction-control parameter. It was found that oleic and stearic acids were effective in retarding the degradation of the BaTiO3 powders. They also made the dissolution rate of the powders in water considerably slower.

The magnetic properties of sputtered Pd/Co multilaysers in hydrogen atmospheres were studied. The x-ray diffraction(XRD) patterns in hydrogen atmospheres showed that the lattice expansion of hydrogenated Pd decreased with decreasing thickness of Pd layers, which is reminiscent of nano-crystalline Pd. Perpendicular magnetic anisotropy(PMA) and saturation magnetization were reduced by the hydrogénation. The interface anisotropy energy per unit area, Ks, and volume anisotropy energy per unit volume, Kv are discussed. These results suggest that interface magnetic anisotropy between Pd and Co layers is suppressed by hydrogenation.

The sensitivity of acoustic techniques to topological and morphological variations in SiC/porous SiC laminated ceramics is studied using a transfer matrix formalism. To implement this transfer matrix technique, the mechanical properties of the SiC porous layers are characterized using the effective medium approximation of Kuster and Toksoz. We show that topological defects have a stronger acoustic signature than morphological defects. Also, we observe that there are particular frequencies at which the defects do not present any acoustic signature.

Polyethyleneterephthalate substrates were coated with thin films of silicone oxide deposited by magnetically enhanced chemical vapor deposition. The rates of oxygen and water vapor transport through the coated and uncoated film systems were obtained as a function of temperature. Activated rate theory treatment of oxygen transmission rates revealed that silicone oxide coatings were imperfect; the apparent free energies of activation (ΔEp) for transport through film substrates which were coated on a single side were statistically identical to uncoated controls. However, multilayer coatings, consisting of two silicone oxide layers separated by an organic layer resulted in a dramatic increase in the ΔEp value. Similar effects were observed in polymer films coated on both sides with identical oxide layers. A simple empirical model for the change in transport mechanism is offered to explain this unanticipated results.

Activated rate theory treatment of water vapor transmission rates for these same film systems showed no obvious change in transport mechanism. However, ΔEp values obtained for water vapor permeation through silicone oxide coated polyethyleneterephthalate, polystyrene, polypropylene, and polycarbonate substrates were identical within experimental error, suggesting attractive interaction between the oxide layer(s) and water.