Analytical electron microscopy (AEM) was used to examine the initial interfacial reaction layers between a eutectic Sn–3.5Ag solder and an electroless nickel-immersion gold-plated (ENIG) Cu substrate during reflow at 255 °C for 1 s. AEM confirmed that a thick upper (Au,Ni)Sn2 layer and a thin Ni3Sn4 layer had formed through the reaction between the solder and ENIG. The amorphous electroless Ni(P) plated layer transformed into two P-rich Ni layers. One is a crystallized P-rich Ni layer, and the other is an intermediate state P-rich Ni layer before the crystallization. The crystallized P-rich layer consisted of Ni2P and Ni12P5. A thin Ni2P layer had formed underneath the Ni3Sn4 layer and is believed to be a predecessor of the Ni2SnP ternary phase. A Ni12P5 phase was observed beneath the Ni2P thin layer. In addition, nanocrystalline Ni was found to coexist with the amorphous Ni(P) phase in the intermediate state P-rich Ni layer.

ZrO2 films deposited on silicon (100) substrates using pulsed-pressure metalorganic chemical vapor deposition (PP-MOCVD) with zirconium n-propoxide (ZnP) Zr(OC3H7)4 were dense and fully crystalline for substrate temperatures of 500 to 700 °C. Film thicknesses were 40 to 815 nm thick, measured after growth using ellipsometry and scanning electron microscopy (SEM). The growth rate was between 0.1 μm/h at 500 °C and 1 μm/h at 700 °C. Transmission electron microscopy (TEM) and x-ray diffraction (XRD) indicated an average grain size of 10 to 20 nm. There was a random orientation of cubic/tetragonal zirconia at the highest experimental temperature of 700 °C. SEM and atomic force microscopy (AFM) was used to characterize island height of discontinuous films in the initial stages of growth where defects in the substrate caused preferred nucleation of isolated particles. At later stages of growth, the average surface roughness of continuous films was 30 nm, which revealed a more uniform growth had developed. A growth model is proposed, and optimal growth conditions are suggested for targeted microstructures of ZrO2 films.

A number of physiological systems involve contact or indentation of solids with tensed surface layers. In this paper the contact problem of spherical indentation of a linear elastic solid, covered with a tensed membrane is addressed. Semianalytical solutions are obtained relating indentation force to contact radius, as well as contact radius to depth. Good agreement is found between derived equations and results from finite element method (FEM) simulations. In addition, effect of membrane on subsurface stresses is shown quantitatively and compared favorably to FEM results. This work is applicable to mechanical property assessment of a number of biological systems.

Aluminum nitride was bonded with a titanium foil at 1400 °C for up to 1 h in Ar. The AlN/Ti interfacial reactions were investigated using analytical electron microscopy. Reaction layers, consisting of δ-TiN, τ2-Ti2AlN, γ-TiAl, α2-Ti3Al, a two-phase region (α2-Ti3Al + α-Ti), and α-Ti (Al, N) solid solution, were observed after annealing at 1400 °C for 0.1 h. Among these phases, the α2-Ti3Al and (α2-Ti3Al + α-Ti) were formed during cooling. Further diffusion of N atoms into the reaction zone precipitates a chopped fiber-like α2-Ti2AlN in the matrix of γ-TiAl, with [110]γ−TiAl//[11¯20]τ2−Ti2AlN and (1¯1¯1)γ−TiAl//(1¯10¯3)τ2−Ti2AlN, by substituting N atoms for one-half Al atoms after annealing at 1400 °C for 1 h. The released Al atoms, due to the precipitation of τ2-Ti2AlN, resulted in an ordered Al-rich γ-TiAl or Ti3Al5. Furthermore, the α-Ti (Al, N) was nitridized into a lamellar layer (δ-TiN + α-Ti) with [110]δ−TiN//[11¯20]α−Ti and (111)δ−TiN//(0001)α−Ti.

With thin solid film usage expanding in numerous technologies, reliable measurements of material properties such as yield strength become important. However, for thin solid films the measurement of yield strength is not readily available, and an alternative method to obtain this property is to measure hardness and convert it to yield strength. Tabor suggested dividing hardness by ∼3 to obtain yield strength, which has been used extensively, despite its shortcomings. Since the pioneering work of Tabor, researchers have performed numerical and experimental studies to investigate the relationships between hardness, yield strength, and elastic modulus, using the indentation technique. In this study, finite element analysis was performed to simulate the nanoscratch technique. Specifically, the nanoscratch finite element analysis was used to validate a previously developed analytical scratch hardness model. A full-factorial design-of-experiments was performed to determine the significant variables for the ratio of calculated scratch hardness to yield strength and a simple analytical prediction model for the ratio of hardness to yield strength was proposed.

A fully dense nanocrystalline (nc) Cu with mean grain size of 72 nm and a broad grain size distribution was synthesized by electrodeposition. Uniaxial tensile tests were done at different strain rates and room temperature. A very high strength of 1.04 G was obtained at strain rate of 0.1 s−1. The nearly perfect plasticity with a large strain of close to 20% was displayed at specific low strain rates of 4 × 10−5 to 10−4 s−1. With increasing strain rate, the nearly perfect plasticity disappeared. Strain rate sensitivity and activation volume of the nc Cu were estimated from the flow stress at a fixed strain of 1% and a strain rate change (jump) test. It was deduced from the high strain rate sensitivity exponent of 0.08 and small activation volume of 12b3 that both dislocation and grain boundary activities would take place in this nc Cu, which explained the nearly perfect plasticity observed in the tensile test.

In the present work, the oxide layers developed at elevated temperature on three vanadium-free titanium alloys, of interest as implant biomaterials, were studied by Rutherford backscattering spectroscopy, elastic recoil detection analysis, and scanning electron microscopy. The chemical composition of the alloys investigated, in wt%, was Ti–7Nb–6Al, Ti–13Nb–13Zr, and Ti–15Zr–4Nb. Upon oxidation in air at 750 °C, an oxide scale forms, with a chemical composition, morphology, and thickness that depend on the alloy composition and the oxidation time. After equal exposure time, the Ti–7Nb–6Al alloy exhibited the thinnest oxide layer due to the formation of an Al2O3-rich layer. The oxide scale of the two TiNbZr alloys is mainly composed of Ti oxides, with small amounts of Nb and Zr dissolved. For both TiNbZr alloys, the role of the Nb-content on the mechanism of the oxide formation is discussed.

The microstructures, interfacial reactions, and bonding strength properties of the Ti–Cu dissimilar joints using a commercially available Ag–28Cu–2Ti filler were studied, particularly as they relate to the role of an Ag barrier layer at the Ti interface. A joint microstructure and interfacial reactions closely related to the formation of brittle interfacial Ti–Cu intermetallics were fully dominated by the presence of the Ag layer at the Ti interface. Reliable Ti(base)/TiAg/Ag/Ag–Cu eutectic/Cu(base) joints without any detrimental Ti–Cu intermetallics were achieved at low brazing temperatures below 810 °C by applying an Ag interlayer of suitable thickness. It was notable that their bonding strengths were strong enough to exceed the strength of a Cu bulk base metal. This research demonstrates the potential application of an Ag interlayer for the reliable Ti–Cu dissimilar joints.

The temperature dependence of the thermal stability in a NiCoCrAlY coating alloy was examined by experimental observation and thermodynamic modeling in the 400–1200 °C temperature range. The results indicated that the thermal stabilities of primary β–NiAl, β–NiAl/α–Cr eutectic, and γ–Ni were slightly temperature dependent, but those of γ′–Ni3Al, σ–(Cr,Co,Ni), and α–Cr were strongly temperature dependent in the annealed NiCoCrAlY specimens. The temperature dependence of the thermal stabilities among γ′–Ni3Al, σ–(Cr,Co,Ni), and α–Cr might be ascribed to the σ → α transformation at ∼1100 °C and the γ′ → γ transformation at ∼800 °C. Further, using Thermocalc associated with TTNi7 database, thermodynamic equilibria were calculated. The modeling results were compared with the experimental results and found to be in reasonable agreement with the experimental observations of β–NiAl, σ–(Cr,Co,Ni), and γ′–Ni3Al. Some deviations observed are discussed in the light of both limited availability of thermodynamic data and experimental problems.

Silicon pack cementation has been applied to improve the oxidation resistance of Zr2Al3C4. The Si pack coating is mainly composed of an inner layer of ZrSi2 and SiC and an outer layer of Al2O3 at 1200 °C. The growth kinetics of silicide coating at 1000–1200 °C obey a parabolic law with an activation energy of 110.3 ± 16.7 kJ/mol, which is controlled by inward diffusion of Si and outward diffusion of Al. Compared with Zr2Al3C4, the oxidation resistance of siliconized Zr2Al3C4 is greatly improved due to the formation of protective oxidation products, aluminosilicate glass, mullite, and ZrSiO4.

In this work, we study the cooling behavior of several typical bulk glassy alloys on casing and present the relationship between the thermal conductivity of a glassy alloy and the cooling rate upon mold casting. The cooling rates obtained for Ti-, Zr-, Pd-, and Cu-based bulk glass forming alloys are found to scale with the thermal conductivities of the studied glassy alloys.