Microstructure Evolution and Shear Strength of Tin-Indium-xCu/Cu Joints

The low melting temperature In-48Sn alloy is a promising candidate for flexible devices. However, the joint strength of the In-48Sn alloy on the Cu substrate was low due to the rapid diffusion of Cu into the In-rich alloy. In this study, the effect of the addition of xCu (x = 2.0 and 8.0 wt.%) on wettability, interfacial reaction, and mechanical strength of the In-Sn-xCu/Cu joint is analyzed. The results demonstrate that both the In-48Sn and In-Sn-xCu alloys exhibit good wettability on the Cu substrate and that the contact angle increases with an increase in the Cu content. Furthermore, fine grains are observed in the alloy matrix of the In-Sn-xCu/Cu joint and the interfacial intermetallic compound (IMC) comprising the Cu-rich Cu6(In,Sn)5 near the Cu substrate and the Cu-deficient Cu(In,Sn)2 near the solder side. The In-Sn-2.0Cu/Cu joint with fine microstructure and a small amount of IMC in the alloy matrix shows the highest average shear strength of 16.5 MPa. Although the In-Sn-8.0Cu/Cu joint also exhibits fine grains, the presence of large number of voids and rough interfacial IMC layer causes the formation of additional stress concentration points, thereby reducing the average shear strength of the joint.

Platinum and gold placer from Tugidak Island, Alaska: Platinum-group minerals and their inclusions, gold, and chromite mineralogy

ABSTRACT Black sand beach placers from Kodiak, Sitkinak, and Tugidak Islands, Alaska, have been mined intermittently for gold and minor platinum-group alloys for more than 100 years. High-grade platinum-rich magnetic separate and accompanying black sand from the southern beach placer of Tugidak Island were studied using electron microprobe WDS and scanning electron microscope EDS; mineral classification and identification were based on these techniques. The major platinum mineral is isoferroplatinum, followed by minor tetraferroplatinum and tulameenite, and rare ferronickelplatinum. Two types of alteration were identified in about 3–4% of the alloy grains: rim formation involving Pt loss and increased Fe, Ni, and/or Cu, and fracturing and vein filling by Cu-rich alloy. Ruthenium-Ir-Os-Pt alloys occur as inclusions and veins as well as form part of composite grains. Ten percent of the alloy grains contain a large variety of platinum-group minerals (PGM). Inclusions of cuprorhodsite, malanite, cuproiridsite, laurite, erlichmanite, cooperite, braggite, bowieite, kashinite, miassite, hollingworthite, irarsite, sperrylite, stillwaterite, genkinite, stibiopalladinite, keithconnite, zvyagintsevite, and probable palladodymite and vincentite were identified. Two unidentified inclusion phases also occur. Most of the PGM inclusions are primary and were trapped by a growing crystal from a melt; some inclusions exhibit textures that suggest trapping of an As,Te,S-rich immiscible melt. Secondary inclusions and evidence of deformation were observed in a few alloy grains. Associated with PGM inclusions or as separate inclusions are various base-metal sulfides. Two silicate-melt inclusions in one isoferroplatinum grain have an andesite–shoshonite composition. Minor gold and Ag-rich gold in the high-grade magnetic separate contain magnetite, pyrrhotite, and chromite inclusions. The gold composition suggests that their sources are the numerous quartz veins and apophyses related to granitoids on Kodiak Island. The composition of the placer chromite is similar to chromite from the Border Ranges mélange fault system and suggests that the Uyak Complex ultramafic and mafic rocks are part of a supra-subduction-zone ophiolite and are the source of the platinum-group minerals.

Role of Nickel Content in One-Way and Two-Way Shape Recovery in Binary Ti-Ni Alloys

The shape recovery characteristics of titanium nickelide with an Ni content of 50.0 at % and 50.7 at % were studied in a wide range of structures obtained as a result of cold drawing with an accumulated true strain of e = 0.52 and subsequent annealing in the 250 to 700 °C temperature range. Shape memory effect (SME) inducing was carried out by bending using a non-isothermal loading mode, which made it possible to reveal implementing elastic strain in the equiatomic alloy up to 12% and thereby increase the total shape recovery by a factor of 1.5. The obtained results prove that the Ni content strongly affects the value and specific features of changes of the shape recovery characteristics with loading strain as well as grain/subgrain size. In equiatomic alloy, the total recovery strain manifests its maximum of 13.5–15% and the recovery strain of 9% at a loading strain range of 12 to 14%. In Ni-rich alloy, the total recovery strain manifests its maximum of 20% and the recovery strain of 14% at a loading strain range of 15 to 21%. The maximum two-way SME value correlates with the residual strain in both alloys and reaches its maximum of 3.0% in a material with a recrystallized structure. Varying the loading strain value under bending in the 11 to 21% range allows regulation of the temperature of shape recovery in Ni-rich alloy in the 45 to 80 °C range.

Impact of the Co/Ni-Ratio on Microstructure, Thermophysical Properties and Creep Performance of Multi-Component γ′-Strengthened Superalloys

The Ni content is a crucial factor for the development of γ′-strengthened Co-based superalloys and some studies have systematically addressed its influence on various properties in model superalloys. In this paper, we report for the first time the influence of the Co/Ni ratio in the more advanced nine-component superalloy ERBOCo-1: exchanging Co and Ni in this Co/Ni-based superalloy while keeping the other alloying elements constants has a big influence on a variety of material properties. The elemental segregation after casting is slightly more pronounced in the alloy with higher Ni-content. Microstructural characterization of this alloy termed ERBOCo-1X after heat-treatment reveals that the precipitates are cuboidal in the Co- and spherical in the Ni-rich alloy, indicating a decrease in the γ/γ′ lattice misfit. Analyzing the elemental partitioning behavior by atom probe tomography suggests that the partitioning behavior of W is responsible for that. Furthermore, it is found that even though Ni exhibits the highest overall concentration, the γ matrix phase is still Co-based, because Ni is strongly enriched in the γ′ precipitates. Creep tests at 900 °C reveal that even though the microstructure looks less favorable, the creep resistance of the Ni-rich alloy is slightly superior to the Co-rich variant.

The Role of Surface Hydroxylation, Lattice Vacancies and Bond Covalency in the Electrochemical Oxidation of Water (OER) on Ni-Depleted Iridium Oxide Catalysts

The usage of iridium as an oxygen-evolution-reaction (OER) electrocatalyst requires very high atom efficiencies paired with high activity and stability. Our efforts during the past 6 years in the Priority Program 1613 funded by the Deutsche Forschungsgemeinschaft (DFG) were focused to mitigate the molecular origin of kinetic overpotentials of Ir-based OER catalysts and to design new materials to achieve that Ir-based catalysts are more atom and energy efficient, as well as stable. Approaches involved are: (1) use of bimetallic mixed metal oxide materials where Ir is combined with cheaper transition metals as starting materials, (2) use of dealloying concepts of nanometer sized core-shell particle with a thin noble metal oxide shell combined with a hollow or cheap transition metal-rich alloy core, and (3) use of corrosion-resistant high-surface-area oxide support materials. In this mini review, we have highlighted selected advances in our understanding of Ir–Ni bimetallic oxide electrocatalysts for the OER in acidic environments.

Experimental Study on Zn-Doped Al-Rich Alloys for Fast on-Board Hydrogen Production

For the purpose of investigating the effect of Zn replacement of In3Sn on the hydrogen production performance of Al-rich alloy ingots, Al-Ga-In3Sn alloys with various Zn dosages (0–5 wt.%) were prepared by a traditional melting and casting technique. The phase compositions and microstructures were characterized using X-ray diffractometer (XRD) and scanning electron microscope (SEM) with an Energy Dispersed X-ray system (EDS). The SEM results indicate that, with a small amount of Zn instead of In3Sn, the number and total area of grain boundary (GB) phases will decrease gradually, and the average single GB area will eventually stabilize. The distribution of Zn in the alloy is similar to that of Ga, and an area with high Zn content appeared in the high-Zn-doped sample. The melting behaviors of Al with other metals were measured by DSC. The reaction of these alloys and water were investigated at different temperatures. Compared with Al-Ga-In3Sn alloy, low addition of Zn changed the composition of GB phase and increased the maximum hydrogen production rate. The reason for the changes in the hydrolysis reaction of Al with the addition of Zn was discussed.

The geometric and electronic structures of a Ag13Cu10(SAdm)12X3 nanocluster

A Cu-rich alloy nanocluster [Ag13Cu10(SAdm)12]X3 is reported, and its geometric and electronic structures are further determined via theoretical calculations.

Microstructural and Mechanical Properties of Binary Ti-Rich Fe–Ti, Al-Rich Fe–Al, and Ti–Al Alloys

Three series of binary, FeTi (Ti-rich), FeAl and TiAl (Al-rich) alloy samples were produced in an argon arc furnace. An annealing treatment of 72 h at 1000 °C was applied to the samples, giving rise to different equilibrium microstructures depending on chemical composition. Their mechanical properties were studied through the determination of elastic constants that measure the stiffness of the elaborated materials. Young’s modulus of the binary alloys was determined using Resonance Ultrasonic Vibration (RUV). The accuracy of this technique was demonstrated. A scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS) and X-ray diffraction (XRD) made it possible to identify intermetallic compounds FeTi and Fe 2 Ti, FeAl and Fe Al 2 , and TiAl and Ti Al 2 in respective systems Fe–Ti, Fe–Al, and Ti–Al. The link between their composition, microstructure, and elastic properties was established.