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Plasma electrolytic oxidation (PEO) treatment has been performed on AZ91 Mg alloy in a silicate-containing alkaline electrolyte to disclose the relationship between second phase and resultant coating. The morphology and corrosion behavior were characterized for PEO coatings on three different AZ91 substrates with microstructures altered by heat treatment. In the presence of β phase, both the substrate and PEO coating exhibit enhanced corrosion resistance with finer and more evenly distributed β phase precipitates. In the as-cast AZ91, the anodized coating displays chemically and morphologically discontinuity on α and β phase with very coarse and defective regions on two-phase boundaries. In aged AZ91 with nano-sized β phase precipitates, the PEO coating shows no obvious difference on two-phase boundaries and is more homogenous with fewer pores and defects. The residual stress values given by X-ray diffraction (XRD) analysis indicate that PEO coating on aged AZ91 with finest β phase has the smallest stress which might be the reason for its improved corrosion resistance under synergetic effect of corrosive ions and residual stress. Conversely, in the absence of β phase, i.e. after solid solution treatment, the coating is characterized by the most inhomogeneous microstructure and the worst corrosion resistance, presumably owing to the absence of protective aluminum-containing oxides in the coating and more severe localized oxidation behavior adjacent to AlMn phase. Understanding the effect of second phase on PEO coating will enable us to optimize porous oxide structures for improved corrosion resistance by properly altering the substrate microstructure. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM) technology was adopted to deposite 2Cr13 thin-wall part using robotic cold metal transfer (CMT) equipment; the process stability, phase identification, microstructural evolution, and tensile properties in different layers were investigated. The results showed that a smooth surface was obtained for each layer due to the stable droplet transfer process, which ensured a stable deposition process. Positions in different layers had no significant influence on the structural aspects of the as-fabricated part according to XRD results. Elongated ferrite grains and fine-grained acicular martensite within the matrix in the top layer were recrystallized, instead of a spatial periodicity of martensite laths within equiaxed ferrite grains in the inner layers. Martensite content was increased gradually away from the base metal in the 05–25 th layers except nearly 100% martensite in the first layer. Long axis of martensite laths was randomly distributed in the X-Y plane in the both top and middle regions, while an epitaxial growth parallel to the building direction was found in the X-Z and Y-Z planes. Higher homogeneous ultimate tensile strength (UTS) and strong anisotropy in poorer ductility were obtained for the AM part when compared with the as-solutioned counterpart. Fracture behavior was transformed from ductile to mixed-mode, and finally to brittle from the 01 st layer to the 25 th layer. [ABSTRACT FROM AUTHOR]

Asymmetric-structured La 5.5 W 0.6 Mo 0.4 O 11.25-δ (LWM) ceramic membranes were fabricated by phase-inversion process followed by sintering. Finger-like pores with distributed small pores extend through most bulk of the membrane and reduce the thickness of the dense layer. The hydrogen permeation properties of the LWM asymmetric membranes were investigated as a function of temperature and H 2 partial pressures in feed gas at the temperature range from 800 °C to 1000 °C. The hydrogen permeation flux as a function of time at 900 °C under humid atmosphere was also investigated. Compared with the conventional symmetric dense LWM membrane, the hydrogen permeation flux through the asymmetric membrane is tripled. Furthermore, the chemical stability of LWM oxides after phase-inversion process and H 2 permeation were confirmed by XRD. [ABSTRACT FROM AUTHOR]

In this work, the morphology, crystallization process and crystal structure of the phase-change material TiSbTe (TST) alloy have been successfully established, which is essential for applying this alloy in phase-change memory. Specifically, atomic force microscopy (AFM) was employed to characterize the as-deposited and post-annealed thin films, and transmission electron microscopy (TEM) analyses of the films annealed in situ were used in combination with selected-area electron diffraction (SAED) and radial distribution function (RDF) analyses to investigate the structural evolution from the amorphous phase to the polycrystalline phase. Moreover, the presence of structures with medium-range order in amorphous TST, which is beneficial for high-speed crystallization, was indicated by the structure factors S(Q)s . The crystallization temperature was determined to be approximately 170 °C, and the grain size varied from several to dozens of nanometers. As the temperature increased, particularly above 200 °C, the first single peak of the rG(r) curves transformed into double shoulder peaks due to the increasing impact of the Ti Te bonds. In general, the majority of Ti atoms were doped into the SbTe lattice and tended to form structural defects, whereas the remainder of the Ti atoms aggregated, leading to the appearance of TiTe 2 phase separation, as confirmed by the SAED patterns, high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images and corresponding energy-dispersive X-ray (EDX) mappings. [ABSTRACT FROM AUTHOR]

Abstract: A series of lead-free piezoceramics of (1− x)K0.5Na0.5NbO3–xBi0.8La0.2FeO3 [(1− x)KNN–xBLF, 0.005≤ x ≤0.04] were synthesized by conventional solid-state sintering. Crystal structures and microstructures of the ceramics were characterized by X-ray diffraction and transmission electron microscopy. X-ray diffraction substantiates the existence of an orthorhombic-tetragonal morphotropic phase boundary (MPB) near x =0.01. Highest electrical performances were observed near the MPB. The maximum remnant polarization, piezoelectric coefficient, and coupling factor were measured as 22.5μC/cm2, 144pC/N, and 0.34, respectively. The effects of BLF on structures and electrical properties were discussed. Our results might be helpful for developing KNN-based piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Abstract: In order to improve the properties of Sn–3.8Ag–0.7Cu and Sn–0.5Cu–0.05Ni solders, 0–0.1wt.% of rare earth Ce was added to the base alloys, and the microstructures were studied. Meanwhile, the solderability of solders on Cu substrate was determined by the wetting balance method, the mechanical properties of soldered joints were investigated by the pull-force test and the fracture morphologies were analyzed. It is found that the new solder alloys possess better solderability than the base solder alloys, and the greatest improvement to the solderability of Sn–3.8Ag–0.7Cu–xCe is obtained with around 0.03–0.05wt.% Ce, while the optimal Ce content is in the range of 0.05–0.07wt.% for Sn–0.5Cu–0.05Ni–xCe solders. The results also indicate that the mechanical properties of soldered joints are improved with increasing Ce addition, with peak mechanical properties at Sn–3.8Ag–0.7Cu–0.03Ce and Sn–0.5Cu–0.05Ni–0.05Ce. The grain sizes of solder alloys are refined due to the addition of Ce, thus the mechanical properties of soldered joints are improved simultaneously. [Copyright &y& Elsevier]