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 Acta Metallurgica Sinica (English Letters)Journal Prestige (SJR): 0.576 Citation Impact (citeScore): 2Number of Followers: 7      Hybrid journal (It can contain Open Access articles) ISSN (Print) 1006-7191 - ISSN (Online) 2194-1289 Published by Springer-Verlag  [2352 journals]
• Retraction Note to: Experimental and Quantum Studies on Adsorption and
Corrosion Inhibition Effect on Mild Steel in Hydrochloric Acid by
Thiophene Derivatives
• Abstract: The editor has retracted this article [1] because Figure 7a-7d, as well as parts of the text, were duplicated from the following articles [2,3].
PubDate: 2019-05-01

• Silver Dopant-Induced Effect on Structural and Optoelectronic Properties
of CdSe Thin Films
• Abstract: Thin films of CdSe and silver (Ag)-doped CdSe have been prepared on glass substrates by thermal evaporation in argon gas atmosphere. X-ray diffraction pattern indicates the presence of hexagonal structure with preferred orientation along (100) plane. Elemental composition of the thin films has been analyzed using energy dispersive X-ray analysis. Scanning electron microscopy has been used to investigate the morphology of the thin films. Transmission electron microscope reveals spherical nature of nanoparticles. A decrease in the band gap due to the formation of band tails in the band gap with increase in Ag doping in CdSe lattice has been observed. Photoluminescence spectra indicate redshift in band edge emission peak with increase in Ag doping in CdSe. Electrical conductivity measurements are also studied, and two types of conduction mechanisms taking part in the transport phenomena are observed. Hall measurements indicate n-type behavior of undoped and Ag-doped CdSe thin films.
PubDate: 2019-05-01

• Effect of Aging Heat Treatment on the Microstructure and Creep Properties
of the Cast Ni-Based Superalloy at Low Temperature
• Abstract: Effect of aging heat treatment on the grain boundary microstructure and creep properties of a cast Ni-based superalloy was investigated. With increasing aging temperature from 750 to 1000 °C, M23C6 carbides along the grain boundaries evolve from fine distributed block, continuous film into the coarse discrete block. Moreover, the M23C6 carbides are mainly enveloped within γ′ layers along grain boundaries during 1000 °C aging. Creep rupture lifetime and elongation at 760 °C and 645 MPa are improved with increasing the aging temperature. In particular, the creep rupture lifetime of the specimens aging at 1000 °C is one order of magnitude higher than that of the specimens aging at 750 °C. The enhancement of ductility induced by the γ′ envelopes plays a significant role in the improvement of creep rupture lifetime.
PubDate: 2019-05-01

• Numerical Investigation on Residual Stresses of the Safe-End/Nozzle
Dissimilar Metal Welded Joint in CAP1400 Nuclear Power Plants
• Abstract: The residual stress evolution in a safe-end/nozzle dissimilar metal welded joint of CAP1400 nuclear power plants was investigated in the manufacturing process by finite element simulation. A finite element model, including cladding, buttering, post-weld heat treatment (PWHT) and dissimilar metal multi-pass welding, is developed based on SYSWELD software to investigate the evolution of residual stress in the aforementioned manufacturing process. The results reveal a large tensile axial residual stress, which exists at the weld zone on the inner surface, leads to a high sensitivity to stress corrosion cracking (SCC). PWHT process before dissimilar metal multi-pass welding process has a great influence on the magnitude and distribution of final axial residual stress. The risk of SCC on the inner surface of the pipe will increase if PWHT process is not taken into account. Therefore, such crucial thermal manufacturing process such as cladding, buttering and post-weld heat treatment, besides the multi-pass welding process, should be considered in the numerical model in order to accurately predict the distribution and the magnitude of the residual stress.
PubDate: 2019-05-01

• Creep Behavior and Life Assessment of a Novel Heat-Resistant Austenite
Steel and Its Weldment
• Abstract: In the present study, creep activation energy for rupture was obtained as 221–348 kJ/mol for 22Cr15Ni3.5CuNbN due to the precipitation-hardening mechanism. The extrapolation strength of creep rupture time of 105 h at 923 K for 22Cr15Ni3.5CuNbN is more valid (83.71 MPa) predicted by the Manson–Haferd method, which is superior to other commercial heat-resistant steels. The tensile creep tests ranging from 180 to 240 MPa at 923 K were conducted to investigate creep deformation behavior of welded joint between a novel heat-resistant austenite steel 22Cr15Ni3.5CuNbN and ERNiCrCoMo-1 weld metal. Apparent stress exponent value of 6.54 was obtained, which indicated that the rate-controlled creep occurred in weldment during creep. A damage tolerance factor of 6.4 in the weldment illustrates that the microstructural degradation is the dominant creep damaging mechanism in the alloy. Meanwhile, the welded joints perform two types of deformation behavior with the variation in applied stress, which resulted from the different parts that govern the creep processing. Also, the morphology evolution of the fracture surfaces confirms the effects of stress level and stress state.
PubDate: 2019-05-01

• Corrosion Behavior of High-Strength Steel for Flexible Riser Exposed to CO
2 -Saturated Saline Solution and CO 2 -Saturated Vapor Environments
• Abstract: The corrosion behavior of high-strength steel used for flexible riser exposed to CO2-saturated saline solution and CO2-saturated vapor environments was studied through immersion experiment and electrochemical corrosion experiment. The corrosion behavior and mechanism of the tested steel were analyzed on the basis of corrosion kinetics, nature of corrosion products, corrosion product morphology, elemental distribution and polarization curves. The experimental results showed that the microstructure of the tested steel was bainitic microstructure. The corrosive activity of the tested steel exposed to CO2-saturated vapor environment was significantly lower than that exposed to CO2-saturated saline solution environment. On prolonging the exposure time, the corrosion rate gradually decreased, the corrosion heterogeneity increased, and the dimensions of FeCO3 crystals gradually became small. At later stages of corrosion, the corrosion current density decreased significantly and the anodic Tafel slope increased, indicating that the corrosion process was strongly inhibited. The corrosion mechanism of low-alloy steel with bainitic microstructure was proposed based on experimental results.
PubDate: 2019-05-01

• Comparative Study on Solid-State and Metastable Liquid-State Aging for
SAC305/Cu Joints
• Abstract: In order to study the influence of the physical state of solder on the interfacial reaction of dip-soldered Sn–3.0Ag–0.5Cu/Cu system, two kinds of experiments were designed, including: (1) solid-state aging between the solder and Cu substrate; (2) liquid-state aging between the metastable supercooled liquid-state solder and Cu substrate. The aging times were 30, 60, 120 and 180 min, respectively, and the aging temperature was 8 °C lower than the melting point of the Sn–3.0Ag–0.5Cu (SAC305) alloy (217 °C). The experimental data revealed that the physical state of the solder obviously affected the formation of the intermetallic compound (IMC), and resulted in the difference in the diffusion of atoms on the interface between the SAC305 solder and Cu substrate. The IMC interface after aging for 30 min presents unique characteristics compared with that of the sample after dip soldering. The IMC interface of solid-state aged SAC305/Cu couple is relatively planar, while the IMC interface under metastable supercooled liquid-state aging conditions presents scallop-like shape.
PubDate: 2019-05-01

• Effect of Al on Expansion Behavior of Mg–Al Alloys During
Solidification
• Abstract: The cooling curves and the change of contraction/expansion during solidification and cooling were tested by using a self-made device which could achieve the one-dimensional contraction instead of three-dimensional contraction of the casting. Then, the effects of Al content (0, 1.1, 3, 5, 10, 12.9, 15, 17, 19, 22, 24 and 30 wt%) on the thermal contraction/expansion of the binary Mg–Al as-cast alloys during solidification were obtained. The results showed that expanding instead of contraction was present in Mg–Al alloys with the addition of 0–30 wt% Al during solidification. The values of expansion significantly increased at first and then decreased with the increase in Al content. And the maximum expansion ratio of 0.44% (maximum expansion value: 0.841 mm) was present in the Mg–15 wt% Al alloy. Contraction instead of expansion occurred once the temperature drops to the temperature corresponding to the expansion value in total, indicating the occurrence of a continuous expansion during the solidification process in mushy zone for the Mg alloys with Al addition of 5–30 wt%. The expansion value in total consisted of two parts: the expansions occurring in the liquid-phase zone and mushy zone. The expansion in liquid zone was present in every Mg–Al alloy, and it contributed to the most proportion of the total expansion value when the Al content in Mg–Al alloy was lower than 10 wt% or higher than 22 wt%. However, the total expansion value was mainly determined by the solidification behavior in mushy zone when the Al content was among 10–22 wt% in Mg–Al alloys.
PubDate: 2019-05-01

• Effects of Phosphorus and Iron on Microstructures and Mechanical
Properties in NiCrFe-Based Alloys
• Abstract: The microstructures and mechanical properties, especially creep properties, of the NiCrFe-based alloys with various contents of phosphorus and iron were investigated. The results showed that the tensile yield strength decreased with increasing iron contents while had no obvious change with the addition of phosphorus. For creep properties, the alloy with 15.8 wt% iron and 0.09 wt% phosphorus possessed the longest creep life (679 h) among all alloys. Only M23C6 was formed in the alloys with low phosphorus contents, while both intergranular M3P and M23C6 precipitated with the increment of phosphorus, which enhanced the strength of grain boundary by hindering the movements of dislocations during creep tests. The reasons for the enhancement of creep life were mainly related to the solid solution strengthening effect of phosphorus and optimization of grain boundary precipitations by phosphorus.
PubDate: 2019-05-01

• Hot Corrosion Behavior of SiO 2 –Al 2 O 3 –Glass Composite Coating on
Ti–47Al–2Cr–2Nb Alloy: Diffusion Barrier for S and Cl
• Abstract: Type I hot corrosion behavior of SiO2–Al2O3–glass composite coating based on Ti–47Al–2Cr–2Nb substrate was investigated in the mixture salt of 25 wt%NaCl + 75 wt%Na2SO4 at 850 °C. The results showed that there was a bidirectional ion exchange between composite coating and the film of mixed salts, and the sodium ion in the molten salts penetrated into the glass matrix of composite coating, while the potassium ion in the glass matrix dissolved into the molten salts. A decrease in hot corrosion rate was achieved for the coated alloy in comparison with the bared substrate due to the composite coating acting as a diffusion barrier to sulfur and chlorine and preventing the molten salts from diffusing to the coating/alloy interface during the hot corrosion exposure. Additionally, the composite coating decreased the oxygen partial pressure at the coating/alloy interface and promoted the selective oxidation of Al to form a protective Al2O3 layer.
PubDate: 2019-05-01

• Thermal Conductivity and Tensile Properties of Carbon Nanofiber-Reinforced
Aluminum-Matrix Composites Fabricated via Powder Metallurgy: Effects of
Ball Milling and Extrusion Conditions on Microstructures and Resultant
Composite Properties
• Abstract: Carbon nanofiber (CNF)-reinforced aluminum-matrix composites were fabricated via ball milling and spark plasma sintering (SPS), SPS followed by hot extrusion and powder extrusion. Two mixing conditions of CNF and aluminum powder were adopted: milling at 90 rpm and milling at 200 rpm. After milling at 90 rpm, the mixed powder was sintered using SPS at 560 °C. The composite was then extruded at 500 °C at an extrusion ratio of 9. Composites were also fabricated via powder extrusion of powder milled at 200 rpm and 550 °C with an extrusion ratio of 9 (R9) or 16 (R16). The thermal conductivity and tensile properties of the resultant composites were evaluated. Anisotropic thermal conductivity was observed even in the sintered products. The anisotropy could be controlled via hot extrusion. The thermal conductivity of composites fabricated via powder extrusion was higher than those fabricated using other methods. However, in the case of specimens with a CNF volume fraction of 4.0%, the thermal conductivity of the composite fabricated via SPS and hot extrusion was the highest. The highest thermal conductivity of 4.0% CNF-reinforced composite is attributable to networking and percolation of CNFs. The effect of the fabrication route on the tensile strength and ductility was also investigated. Tensile strengths of the R9 composites were the highest. By contrast, the R16 composites prepared under long heating duration exhibited high ductility at CNF volume fractions of 2.0% and 5.0%. The microstructures of composites and fracture surfaces were observed in detail, and fracture process was elucidated. The results revealed that controlling the heating and plastic deformation during extrusion will yield strong and ductile composites.
PubDate: 2019-05-01

• Formation of Vacancy-Type Dislocation Loops in Hydrogen-Ion-Implanted
Fe–Cr Alloy
• Abstract: Fe–10 at.%Cr alloy was implanted with hydrogen ions at room temperature, followed by annealing at high temperatures. The annealing process made the defects develop into large dislocation loops. The nature of the dislocation loops formed after annealing was studied by the evolution of loops under in situ electron irradiation in high-voltage electron microscope. It indicated that only interstitial-type loops were observed when annealed at 550 °C and below, but vacancy-type loops started to form at the temperature higher than 600 °C. According to the previous study of our group, the presence of chromium element made the formation temperature of vacancy-type loops higher than that in pure iron. The effect of alloying elements on the formation temperature of the vacancy-type loops was discussed.
PubDate: 2019-05-01

• Microalloying Effect of Sn on Phase Transformation During Heat Treatment
in Mg–Y–Zn–Zr Alloys
• Abstract: The microstructure and mechanical properties of the as-cast and heat-treated Mg–4.6Y–2.5Zn–0.6Zr–xSn (x = 0, 0.2 and 0.5 wt%) alloys were investigated in this work. The results showed that the eutectics have been refined with 0.2% Sn addition and it has no effect on the phase category of the alloys. However, Sn3Y5 phase was found in 0.5% Sn-added alloy. After heat treatment at 520 °C, the transformation of the long-period stacking ordered (LPSO) phase takes place in the Mg–Y–Zn–Zr alloy, but the transition is not completed in the alloys containing Sn. In addition, during the heat treatment, the mechanical properties of Sn-free alloys are significantly improved, and the strength of alloys containing Sn does not change much. Through observation and analysis of the microstructure and mechanical properties, it is found that Sn addition hinders the process of α′-Mg → α-Mg + 14H and the process is the key to the transition of 18H-LPSO to 14H-LPSO.
PubDate: 2019-05-01

• Effect of pH on the Electrochemical Behaviour and Passive Film Composition
of 316L Stainless Steel
• Abstract: The effect of pH on the electrochemical behaviour and passive film composition of 316L stainless steel in alkaline solutions was studied using electrochemical measurements and a surface analysis method. The critical pH of 12.5 was found for the conversion from pitting corrosion to the oxygen evolution reaction (OER). OER was kinetically faster than pitting corrosion when both reactions could occur, and OER could postpone pitting corrosion. This resulted in pitting being initiated during the reversing scan in the cyclic polarization at the critical pH. According to the X-ray photoelectron spectroscopy analysis, the content of Cr and Mo decreased with pH, while Fe content increased. This induced the degradation of the passive film, which resulted in the higher passive current densities under more alkaline conditions. The selective dissolution of Mo at high pH was found, which demonstrated that the addition of Mo in austenitic stainless steels might not be beneficial to the corrosion resistance of 316L in strong alkaline solutions.
PubDate: 2019-05-01

• Numerical Simulation of Macrosegregation Caused by Thermal–Solutal
Convection and Solidification Shrinkage Using ALE Model
• Abstract: Solidification shrinkage has been recognized as an important factor for macrosegregation formation. An arbitrary Lagrangian–Eulerian (ALE) model is constructed to predict the macrosegregation caused by thermal–solutal convection and solidification shrinkage. A novel mesh update algorithm is developed to account for the domain change induced by solidification shrinkage. The velocity–pressure coupling between the non-homogenous mass conservation equation and momentum equation is addressed by a modified pressure correction method. The governing equations are solved by the streamline-upwind/Petrov–Galerkin-stabilized finite element algorithm. The application of the model to the Pb-19.2 wt%Sn alloy solidification problem is considered. The inverse segregation is successfully predicted, and reasonable agreement with the literature results is obtained. Thus, the ALE model is established to be a highly effective tool for predicting the macrosegregation caused by solidification shrinkage and thermal–solutal convection. Finally, the effect of solidification shrinkage is analyzed. The results demonstrate that solidification shrinkage delays the advance of the solidification front and intensifies the segregation.
PubDate: 2019-04-16

• Modeling the Dynamic Recrystallization of Mg–11Gd–4Y–2Zn–0.4Zr
Alloy Considering Non-uniform Deformation and LPSO Kinking During Hot
Compression
• Abstract: Hot compression tests of Mg–11Gd–4Y–2Zn–0.4Zr alloy (GWZK114) were conducted at a deformation temperature range of 300–500 °C and a strain rate range of 0.01–10.0 s−1. Based on systematic microstructure observation, it is confirmed that long period stacking ordered (LPSO) phase displays essential and evolving roles on the dynamic recrystallization (DRX) behavior. The results indicate that the plastic deformation is mainly coordinated by simultaneous exist of LPSO kinking of lamella 14H-LPSO phase and DRX at 350–450 °C, and DRX at 500 °C. Further, it is found that the LPSO kinking induced during 350–450 °C can delay the DRX. A phenomenological DRX model of GWZK114 alloy is established to be $$X_{\text{DRX}} = 1 - \exp [ - 0.5(\frac{{\varepsilon - \varepsilon_{\text{c}} }}{{\varepsilon^{*} }})^{0.91} ]$$ . Non-uniform distribution of plastic strain during compression was considered via finite element method and it ensures a good prediction of DRX fraction under a large plastic strain. Meanwhile, an enhanced DRX model, taking its formulation as $$X_{\text{DRX}} = \{ 1 - \exp [ - 0.5(\frac{{\varepsilon - \varepsilon_{c} }}{{\varepsilon^{*} }})^{0.91} ]\} (\frac{T}{226.8} - 1)^{n}$$ , $$n = 3.82\dot{\varepsilon }^{0.083}$$ , is proposed for the first time to capture the hindering effect of 14H-LPSO kinking on DRX behavior. The predicted results of this enhanced DRX model agree well with the experimental cases, where 14H-LPSO kinking is dominated or partially involved (300–450 °C). Besides, a size model of DRX grains is also established and can depict the evolution of DRX grain size for all the investigated compression conditions with accounting for temperature rising at high strain rates (5 s−1 and 10 s−1).
PubDate: 2019-04-16

• Stern–Geary Constant for X80 Pipeline Steel in the Presence of Different
Corrosive Microorganisms
• Abstract: The Stern–Geary constant (B value) is indispensable to measure the corrosion rate in the microbiologically influenced corrosion (MIC) systems. Linear polarization resistance (LPR) and weight loss methods were used to study the variation of B values for X80 pipeline steel in the presence of Pseudomonas aeruginosa, Acetobacter aceti and Desulfovibrio vulgaris. The results showed that B values in the presence of three different bacteria were 35.60 ± 0.55 mV, 33.00 ± 1.00 mV and 58.60 ± 0.55 mV, respectively, suggesting that the change of corrosion system significantly affected the B values of X80 pipeline steel. This work further indicated that the determination of B values is necessary to accurately measure the MIC rate by LPR method.
PubDate: 2019-04-12

• Biodegradation Behavior of Coated As-Extruded Mg–Sr Alloy in
Simulated Body Fluid
• Abstract: As-extruded Mg–Sr alloy, a kind of promising biodegradable biomedical material, was coated using micro-arc oxidation and also using a phosphate conversion coating. The corrosion behaviors were investigated using Hanks’ solution. The corrosion of the as-extruded Mg–Sr alloy became more serious with increasing immersion time; that is, the corrosion pits became more numerous, larger and deeper. The micro-arc oxidation coating and the phosphate conversion coating were effective in improving the corrosion resistance of the as-extruded Mg–Sr alloy. The micro-arc oxidation coating was much more effective. Moreover, the as-extruded Mg–Sr alloy and the coated as-extruded Mg–Sr alloy exhibited lower corrosion rates than the as-cast Mg–Sr alloy and the corresponding coated as-cast Mg–Sr alloy, indicating that the corrosion properties of the coated samples are dependent on their substrates. The finer microstructure of the substrate of the as-extruded condition corroded much slower. The corrosion resistance of the coated Mg–Sr alloy depended on the coating itself and on the microstructure of the substrate.
PubDate: 2019-04-10

• Evolution of Microstructure, Residual Stress, and Tensile Properties of
Mg–Zn–Y–La–Zr Magnesium Alloy Processed by Extrusion
• Abstract: The microstructure, texture, residual stress, and tensile properties of Mg–6Zn–2Y–1La–0.5Zr (wt%) magnesium alloy were investigated before and after extrusion process, which performed at 300 °C and 400 °C. The microstructural characterizations indicated that the as-cast alloy was comprised of α-Mg, Mg–Zn, Mg–Zn–La, and Mg–Zn–Y phases. During homogenization at 400 °C for 24 h, most of the secondary phases exhibited partial dissolution. Extrusion process led to a remarkable grain refinement due to dynamic recrystallization (DRX). The degree of DRX and the DRXed grain size increased with increasing extrusion temperature. The homogenized alloy did not show a preferential crystallographic orientation, whereas the extruded alloys showed strong basal texture. The extrusion process led to a significant improvement on the compressive residual stress and mechanical properties. The alloy extruded at 300 °C exhibited the highest basal texture intensity, the compressive residual stress and hardness, and yield and tensile strengths among the studied alloys.
PubDate: 2019-04-09

• Element Segregation and Solidification Behavior of a Nb, Ti, Al
Co-Strengthened Superalloy ЭК151
• Abstract: The as-cast microstructure, element segregation and solidification behavior of a multi-alloyed superalloy ЭК151 have been investigated. The results show that the severe element segregation leads to the complicated precipitations at the inter-dendritic region, including η-Ni3(Ti, Nb), eutectic (γ + γ′) and Laves, which shows the characteristics of both Ti, Al-strengthened and Nb-strengthened alloys. Differential thermal analysis, heating and quenching tests reveal the solidification sequence as follows: Liquids → γ matrix → (Nb, Ti)C → η-Ni3(Ti, Nb) → eutectic (γ + γ′) → Laves. The melting points are between 1250 and 1260 °C for (Nb, Ti)C, between 1200 and 1210 °C for η phase, between 1180 and 1190 °C for eutectic (γ + γ′) and Laves. γ′ initially precipitates from matrix at 1150 °C and achieves the maximum precipitation at 1130 °C. According to the microstructure evolution captured during solidification and composition analysis by an energy dispersive spectrometer and electron probe microanalyzer, (Nb, Ti)/Al ratio is put forward to explain the formation of η-Ni3(Ti, Nb) and eutectic (γ + γ′). The solidification of γ matrix increased the Nb, Ti concentration in the residual liquids, so the high (Nb, Ti)/Al ratio would result in the formation of η-Ni3(Ti, Nb); the precipitation of the phase consumed Nb and Ti and decreased the (Nb, Ti)/Al ratio in the liquid, which led to the precipitation of eutectic (γ + γ′). Laves formed by the sides of η-Ni3(Ti, Nb) and in front of the eutectic (γ + γ′) after Al, Ti were further depleted by the two phases and Cr, Co, Mo were rejected to liquids.
PubDate: 2019-04-09

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