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The high-temperature oxidation behaviour of SPS-prepared Mo and Mo–5Ta alloys are investigated under the temperature range 300–700°C for 0–120 min in static air condition. The oxidation weight gains of Mo and Mo–5Ta conform to parabolic law at different oxidation times of 500°C and all remain at low levels. At low temperature (≤ 500°C), the oxidation resistance improves with Ta addition. However, at 600°C and 700°C, the oxidation of Mo–5Ta increases and the weight gain is obvious. Compared with pure Mo, a continuous and dense oxide scale can be formed quickly on the surface of Mo–5Ta alloys during the oxidation process at 500°C, which improves the oxidation resistance of the alloys. The volatile MoO3 and generated Ta2O5 above 500°C cause more voids to form in the matrix, resulting in the deterioration of the oxidation resistance of the alloys. [ABSTRACT FROM AUTHOR]

Herein, single‐pass laser‐cladded 2205 duplex stainless steel is fabricated on the surface of Q235 carbon steel at different laser powers in the range of 1.7−2.7 kW. The relationships between laser powers and geometrical characteristics, microstructure, microhardness, and corrosion resistance of the cladded layers (CLs) are analyzed. The results show that with the increase in laser power, the width and height of the bead increase, and the dilution rate and depth of the molten pool also significantly increase. Furthermore, the shape of ferrite gradually transforms from coarse to slender and eventually turns into a discontinuous vermicular shape. It is found that the CL obtained at a laser power of 2.3 kW has higher average microhardness and exhibits better corrosion resistance than the other samples (≈20 times better than that of the carbon steel substrate), with its corrosion potential and corrosion current density of −0.146 V and 0.13 μA cm−2, respectively. [ABSTRACT FROM AUTHOR]

The relationships between composition, microstructure and electrochemical properties are of fundamental importance in understanding the corrosion of multiphase materials and thus in aiding in the design of new materials. A local electrochemical test system which combines a capillary device with a photolithographic mask has been developed to investigate the local electrochemical properties of a predefined micron-sized area with greater reliability and versatility than existing approaches. Independent electrochemical measurements were conducted on the different phases of a 2205 duplex stainless steel in NaCl solution, demonstrating the feasibility of the developed test system. [ABSTRACT FROM AUTHOR]

Copper foil electrodeposition has been explored using a pure titanium rotating disk electrode (RDE) in acidic electrolytes containing gelatin and/or chloride ions under different convection conditions. In the plating bath without gelatin, the results indicate that stronger convection promotes hydrogen evolution, which reduces the current efficiency during copper plating. Gelatin restrains the growth of copper grains in the lateral direction parallel to the surface. This results in grain refinement on the shiny side, an increase in local grain misorientation and in internal stresses on both the shiny and the matte side, and a reduction in their internal stress difference. At strong convection conditions and with gelatin present, copper deposits as strip-like grains along the centrifugal direction of the cross section, and finally forms a spiral-shaped pattern on the matte side. The causes of these features are discussed in detail. The combined influences of hydrogen and gelatin adsorption are further elaborated in a model for a copper deposition. The current investigation suggests that a moderate convection (somewhat lower than 1000 rpm) and a concentration of 2 ppm gelatin in the plating bath are sufficient for copper foil fabrication in the presence of chloride ions (20 ppm). [ABSTRACT FROM AUTHOR]

• The role of slag chemistry on properties and microstructure of AAS is revealed. • The correlation between NBO/T of slag and properties of AAS is discussed. • Evidence on the beneficial role of hydrotalcite on AAS properties is provided. Aiming at uncovering the critical chemical parameters that govern the performance of alkali-activated slag (AAS), this work investigates the phase assemblage, microstructure, and setting and mechanical properties of AAS prepared using five different slags and two activators (sodium hydroxide or sodium carbonate). The results suggest that the ratio of non-bridging oxygens to tetrahedral cations (NBO/T) of slag structure is an appropriate reactivity indicator, correlating reasonably well with the mechanical performance of AAS at late ages. However, the NBO/T value of slag structure is relatively incompetent in indicating the setting performance of AAS, particularly for the sodium carbonate-activated system. The variability of slag chemistry has considerable impacts on the setting behaviors of AAS, but relatively insignificant effects on compressive strength, suggesting that the strength of AAS is dominated by activator and mixture proportioning parameters. Regardless of activator chemistry, the AAS with a higher amount of hydrotalcite formation tends to have higher compressive strength, implying the beneficial roles of hydrotalcite in microstructure densification and strength achievement. [ABSTRACT FROM AUTHOR]

Abstract: 90W(Mo)–Ni–Fe heavy alloy with gradient structure was fabricated by the diffusion of Mo slice from the alloy's surface at 1480°C. The microstructure and content of binding phase at different regions along the cross section in the samples were investigated by scanning electron microscopy (SEM). The Mo content was determined by energy dispersive analysis (EDS) and the hardness of matrix phase was measured by Vickers' micro-hardness tester. Results show that the grain size, the volume fraction of binding phase and the hardness of matrix phase vary gradually due to the graded distribution of molybdenum. Simultaneously, the interfacial tension gradient induced by the dissolution of molybdenum is the driving force for liquid phase migration during liquid phase sintering. [Copyright &y& Elsevier]

By applying 2205 duplex stainless steel powders to repair and improve carbon steel, multi-pass laser-cladding tests were conducted on Q235 carbon steel surfaces with different laser powers in the range of 1.9~2.5 kW in order to evaluate the performance of the laser-cladding layers. The phase composition, macro- and microstructure, electrochemical corrosion resistance, friction, and wear resistance of the laser-cladding layers were investigated. Macroscopic observation identified no obvious cracks. The phases that made up the multi-pass laser-cladding layers were γ-Fe and α-Fe. Owing to the optimal laser power at 2.3 kW, a large number of equiaxed crystals and a small number of cellular crystals made up the microstructure of the prepared laser-cladding layer, which contributed to its good corrosion resistance. The wear resistance of the multi-pass laser-cladding layer and the carbon steel was also studied. A combined action of adhesive wear and abrasive wear, accompanied by oxidative wear, was determined through observation of pits and furrows on the friction surface of the multi-pass laser-cladding layer, while a typical mechanism of abrasive wear was confirmed by checking the friction surface of the carbon steel. [ABSTRACT FROM AUTHOR]

The effect of welding speed on microstructure, mechanical properties, and corrosion properties of laser-assisted welded joints of a twinning-induced plasticity (TWIP) steel was investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) analysis, electrochemical test, and micro-area scanning Kelvin probe test (SKP). The results reveal that the welded joints, with a fully austenitic structure, are obtained by laser welding. In addition, the preferred orientation of grains in fusion zone (FZ) increased with the increase of welding speed. Additionally, the coincidence site lattice (CSL) grain boundaries of FZ decreased with increasing welding speed. However, potentiodynamic polarization and SKP results demonstrated that the welding speed of 1.5 m/min renders superior corrosion resistance. It can also be inferred that the corrosion properties of the welded joints are related to the grain size and frequency of CSL grain boundary in FZ. [ABSTRACT FROM AUTHOR]

The influence of chloride deposition on the formation, evolution and barrier properties of the patina formed on Cu5Zn5Al1Sn used for architectural cladding is explored via long-term marine field exposures and laboratory investigations. The presence of Cu 2 O, ZnO, Al 2 O 3 and SnO 2 within the inner part of the patina and intercalation of SnO 2 , Zn 5 (CO 3 ) 2 (OH) 6 , Zn 6 Al 2 (OH) 16 CO 3 ·4H 2 O, Zn 5 (OH) 8 Cl 2 ·H 2 O within its outer part, predominantly composed of Cu 2 (OH) 3 Cl, significantly reduce the chloride-induced corrosion compared with Cu metal. The intercalation of zinc-rich corrosion products within the patina and not at the top-surface explain their marginal influence on the runoff process that mainly occurs at the outmost surface. [ABSTRACT FROM AUTHOR]

Abstract: Spraying microarc oxidation (SMAO) equipment, consisting of a mini microarc oxidation (MAO) power source and a movable spraying polar, was employed to solve the problem that field repair of local damage area on workpiece and larger workpiece cannot be immersed in the electrolyzer for conventional microarc oxidation (CMAO) process. SMAO coatings were fabricated on the surface of 2024 Al alloy samples using a self-made SMAO equipment system. Electrochemical techniques were employed to evaluate the corrosion resistance of CMAO and SMAO coatings in 3.5wt.% NaCl solution. The results indicated that SMAO coating is thinner than CMAO coating under the same experimental conditions. SMAO coating treated for 10min can be easily penetrated by the test solution, while treated for 20 and 30min, the coatings with much better corrosion resistance can be fabricated. [Copyright &y& Elsevier]

In the present work, 90W–6Ni–4Mn alloy was prepared by an atmospheric controlling method, which can avoid the oxidation of elemental Mn during sintering, to obtain full density. Different sintering temperatures and holding times were employed to optimize the sintering process. Relative densities higher than 99.0% were achieved for 90W–6Ni–4Mn sintered at temperatures of 1200–1300 °C with various holds. Nearly full density of 99.65% was acquired with an average W grain size of 12.6 μm as sintered at 1250 °C for 60 min. When subjected to tensile testing, this alloy exhibits an ultimate tensile strength of 981 MPa and elongation of 20.6%. Higher sintering temperatures and longer holding times resulted in higher W content in the matrix phase, solid volume fraction and contiguity, due to solution–reprecipitation and grain coalescence during liquid phase sintering. Moreover, under such a circumstance, the insoluble inert gas (argon) trapped in residual closed pores caused the pores to coarsen, deteriorating the density and tensile properties of 90W–6Ni–4Mn alloy. Accordingly, a suitable sintering cycle is fundamental for full density 90W–6Ni–4Mn alloy with mechanical properties comparable to conventional tungsten heavy alloys, but 200–250 °C lower sintering temperature. [ABSTRACT FROM AUTHOR]

Abstract: In the processing of W–Ni–Mn heavy alloys, the affinity of manganese to oxygen and the reduction of its oxides during sintering should be considered. In this work, an atmospheric controlling method was proposed to solve these problems. The sintering cycle consisted of a heating up to 600°C in vacuum, holding after the atmosphere changed to an argon gas, and sintering at temperatures from 1050 to 1200°C. Densities around 99.7% for the 90W–4Ni–6Mn alloys were obtained with sintering temperatures in the 1100–1200°C range. Compared to the conventional heavy alloys, relatively lower temperature results in a finer grain size (6–10μm) after densification and consequently better performance in tensile test. A 1030MPa ultimate tensile strength with a 25% elongation to failure was achieved when sintered at 1150°C. Worth mentioning that grain coalescence plays as a typical coarsening mechanism in the case of the 90W–4Ni–6Mn alloy, and insufficient coalescence process could lead to a poor performance in elongation. These results show that by selecting a suitable sintering cycle, the 90W–4Ni–6Mn alloy with properties comparable to the W–Ni–Fe system can be obtained but with sintering temperatures 300°C lower. [Copyright &y& Elsevier]

Abstract: Ternary Mg–Co–B alloys have been successfully synthesized by a chemical reduction method with subsequent heat-treatment at various temperatures. The products thus obtained have been investigated as anode materials in alkaline aqueous KOH+LiOH co-solution. The as-prepared Mg–Co–B alloys have been found to show excellent electrochemical reversibility, as well as considerably high specific capacities of up to 336mAh/g. The outstanding electrochemical performances of the Mg–Co–B alloys are shown to stem from their specific microstructures, which have been characterized by X-ray diffraction, scanning electron microscopy, BET surface area measurement, and cyclic voltammetry. [Copyright &y& Elsevier]