Search

The effect of coupling of copper and phosphorus in steel on atmospheric corrosion behavior was investigated using high-throughput experimental methods. Wire beam electrodes and plates with discrete distribution of composition gradients were prepared through a selective laser melting method. By combining array electrode scanning tests and EPMA, the electrochemical properties and the relationship between different copper and phosphorus contents were rapidly determined. Plenty of data obtained were analyzed according to relevant standards and screened to identify compositional ranges corresponding with the relevant compositions of existing grades of steel. To further analyze the effect of copper and phosphorus on the corrosion behavior, dry/wet cyclic corrosion test were performed using plates. A combination of XRD, FTIR, SEM, EDS, and EPMA were used to analyze the corrosion behavior. It was observed that both copper and phosphorus promoted the formation of amorphous substances, supporting the proposed mechanism by previous researchers. Furthermore, in the absence of manganese interference, copper could accumulate at the metal/rust layer interface, rendering the rust layer cation-selective and effectively inhibiting the deep penetration of chloride ions. Moving forward, we expect to develop this high-throughput experiments to investigate the coupling effects of other elements on corrosion behavior.

The corrosion resistance of ferrous alloys is greatly influenced by the presence of alloying elements, however, predicting the coupling effects of these elements remains a challenge. In the present paper, the effects of various alloying elements on the corrosion resistance of iron matrix material were investigated using high-throughput density functional theory (DFT) calculations. This work explores the dissolution behavior of metal and alloy surfaces and established correlations between calculated parameters and experimentally measurable values to predict polarization curves and simulate corrosion behavior. The results showed that doping with Cu, P, Ni, Al, Mn, Co, Si, Ti, and Zn on the Fe (110) surface can reduce the corrosion current density of the iron matrix. For Fe-Cu and Fe-Mn steels, coupling P-Ti in Fe-Cu steel and P-Si in Fe-Mn steel can significantly improve their corrosion resistance. The developed model can quantitatively predict material properties and efficiently screen compositions to design corrosion-resistant alloys.

White Etching Layer (WEL) and Brown Etching Layer (BEL) always form on the surface of rails and bearings subjected to rolling cyclic contact stress. Because of the different properties between WEL/BEL and matrix, the cracks initiate and propagate easily, leading to failure ultimately. The WEL and BEL found on pearlite rail, have been widely investigated, but WEL and BEL on bainite rail and martensite bearing have not been further studied. Especially the BEL on martensite bearing raceways has rarely been reported. This study investigates the features of WEL and BEL found on martensite bearing raceway. The BEL locates in the middle of WEL and matrix, but its hardness values are the highest, which is different from the general results reported: WEL > BEL > matrix. The WEL is mainly consisted of austenite with coarse grains, ferrite and retained tempered martensite. The mainly composition of BEL is quenched martensite. Thermal effect is the main formation mechanism of the WEL and BEL in this study. BEL forms because the surface temperature exceeds Acm point, and then rapidly decreases. The formation of WEL may originate from two processes: (1) The austenitizing and slowly cooling process again of BEL; (2) The austenitizing and slowly cooling process of the matrix. WEL and BEL forming processes are closely related to the diffusion and redistribution of carbon. The contributory heat conduction and diffusion mechanism in the confined spaces of grease lubricated bearings have been also discussed in this study.

The effect of HCO3− and Cl− on the corrosion behavior of Q345 carbon steel in soil simulated solutions was investigated through electrochemical and surface characterizations. The results show that the sample behaves with active dissolution state in low concentration of Cl− solution while pseudo passivation of sample is observed in high concentration of Cl− solution. However, in solutions containing low concentration of HCO3−, the addition of high concentration Cl− does not result in the pseudo passivation of sample due to the formation of discontinuous film, which increases the corrosion rate. In addition, in solution containing high concentration of HCO3−, the addition of high concentration Cl− leads to much higher increase of corrosion rate. The deep corrosion pit is observed on the matrix due to the rapid rupture of FeCO3 film and the sufficient development of pitting.

White etching layers (WELs) and brown etching layers (BELs), formed on the upper layer of bearing raceways generally lead to surface crack initiation and propagation and significantly affect the stable operation of precision bearings. In this study, the microstructure features of WELs and BELs from two failure bearings have been characterized and analyzed. The BEL mainly consists of quenched martensite with higher hardness values. The bainite simultaneously exists at the boundary of the BEL/matrix. Owing to the relative roll and slip, temperature increases and rapid decreases are the main formation mechanisms of the BEL in this study (thermal-induced effect). The WEL can be only found on one sample, and elongated and coarse grains are found in this region. It can be speculated that the WEL may originate from the surface region temperature increasing again and then slowly decreasing. Cracks can initiate at the boundaries of the WEL/BEL/matrix. The crack propagation behaviors are significantly affected by the properties of the WEL and BEL microstructure. It is difficult for the cracks to propagate from a softer WEL into a harder BEL. Thus, the depth of cracks in the WEL is shallower. However, because of the brittle nature of quenched martensite in the BEL, cracks can easily propagate downward under contact stress. Thus, the depth of cracks can exceed 100 μm easily. The formation mechanisms of the WEL/BEL and crack propagation behaviors have been further proved and discussed in this study.

The optimization of water chemistry in pressurized water reactor (PWR) primary circuit is one of the most effective ways to achieve both safety and economy for operating PWR nuclear power plants (NPPs). Special attention has been paid to fundamental research and engineering application of Zn-injection water chemistry (ZWC) in PWR primary circuit in recent years in China due to the rapid development of nuclear power. The present paper mainly reports the status of PWR NPPs in China and some fundamental understandings of ZWC on material corrosion. Effects of temperature (T), pH at T value, Zn concentration, Zn-injection sequence and lasting time on electrochemical corrosion behavior, oxide film characteristic and stress corrosion cracking (SCC) susceptibility of nuclear-grade austenitic alloys were investigated. A modified point defect model was used to discuss the effects of ZWC on the oxide films in high-temperature pressurized water. Some water chemistry parameters in PWR primary coolant system are proposed for mitigating corrosion and SCC of nuclear-grade austenitic alloys.

Corrosion fatigue crack growth (FCG) behavior of 316LN stainless steel was investigated in high-temperature pressurized water at different temperatures, load ratios (R = Kmax/Kmin) and rise times (tR). The environmental assisted effect on FCG rate was observed when both the R and tR exceeded their critical values. The FCG rate showed a linear relation with stress intensity factor range (ΔK) in double logarithmic coordinate. The environmental assisted effect on FCG rate depended on the ΔK and quantitative relations were proposed. Possible mechanisms of environmental assisted FCG rate under different testing conditions are also discussed.

Low cycle fatigue behaviors of SA508-3 low-alloy steel were investigated in room-temperature air, high-temperature air and in light water reactor (LWR) water environments. The fatigue mean curve and design curve for the low-alloy steel are developed based on the fatigue data in room-temperature and high-temperature air. The environmental fatigue model for low-alloy steel is developed by the environmental fatigue correction factor (Fen) methodology based on the fatigue data in LWR water environments with the consideration of effects of strain rate, temperature, and dissolved oxygen concentration on the fatigue life.

Coatings on the surface of Mg alloys are inevitably damaged during their practical applications, and corrosion can easily initiate from the damaged areas to accelerate the failure of Mg parts. A dual self-healing coating has already been developed to solve this problem in our previous work. Considering the practical application of this coating, it is necessary to investigate its service behavior in atmospheric environment. Thus, the corrosion behavior of AM60 Mg substrate with and without the self-healing coating was compared in Shenyang industrial atmospheric environment. The results show that the enrichment of sediments and rainwater on the scratch areas can accelerate the corrosion of the exposed Mg substrate. The inhibitors can be released from the damaged coating to inhibit corrosion. The dual self-healing coating shows better inhibition ability to narrow scratches due to the higher inhibitor concentration and less resumption. Also, the coating with wide scratches displays enough inhibition ability as well. The dual self-healing coating is a good alternative for Mg alloy parts in the practical applications.

The grain growth process plays an important role in the texture formation in magnesium alloys. The microstructural and micro-textural evolution of a cold-rolled Mg–Zn–Gd alloy during annealing at 350 °C for 60–190 min were tracked by quasi-in-situ electron backscatter diffraction method. The results show that grain growth takes place gradually with the annealing time increasing. Moreover, the TD-split texture maintains the texture type but alters in three aspects - the increased tilting angle, the decreased pole intensity and the widened distribution of high-intensity area. Grains with their c-axis tilting 45–70° from normal direction show preferential growth which is closely associated with the texture changes. The original grain size advantage is one of the important factors leading to the growth advantage, some grain boundaries, such as 50–60° [1¯21¯0], 50–60° [2¯75¯0], 60–70° [1¯21¯0] (∑18b), and 70–80° [101¯0] (∑10) are also considered to be related to this preferential growth.

Abstract Grain boundary (GB) oxidation of proton-irradiated 304 nuclear grade stainless steel in primary water of pressurized water reactor was investigated. The investigation was conducted by studying microstructure of the oxide and oxide precursor formed at GB on an "atom-by-atom" basis by a combination of atom-probe tomography and transmission electron microscope. The results revealed that increasing irradiation dose promoted the GB oxidation, in correspondence with a different oxide and oxide precursor formed at the GB. Correlation of the oxide and oxide precursor with the GB oxidation behavior has been discussed in detail.

Crevice corrosion behavior of Alloy 690 in high-temperature aerated chloride solution was studied using a self-designed crevice device. The SEM, EDS, XRD, and XPS analyses results indicated that the oxide films outside the crevice consisted of Ni-Cr oxides containing a small amount of hydroxides, and the oxide films on crevice mouth consisted of a (Ni,Fe)(Fe,Cr)2O4 spinel oxides outer layer and a Cr(OH)3 inner layer, and the oxide films inside the crevice consisted of a α-CrOOH outer layer and a Cr(OH)3 inner layer. When crevice corrosion occurred, the hydrolysis of Cr3+ led to the formation of Cr(OH)3 inside the crevice, and caused the pH value of crevice solution to decrease, and Cl− migrated from outside the crevice into inside the crevice due to electrical neutrality principle and accumulation. When the water chemistry inside the crevice reached the critical value of active dissolution of metal, the active dissolution of metal inside the crevice occurred. In addition, (Ni,Fe)(Fe,Cr)2O4 spinel oxides on the crevice mouth were formed by the deposition of metal ions migrated from inside the crevice. The mechanism of crevice corrosion and the formation mechanism of oxide films at different regions were also discussed.

A SnO2-doped dicalcium phosphate coating was prepared on AZ31 alloy by means of hydrothermal deposition. The results showed that the coating possessed a globular morphology with a long lamellar crystalline structure and a thickness of approximately 40 μm. The surface of the coating became smooth with an increase additive amount of the SnO2 nanoparticles. The corrosion current density and hydrogen evolution rate of the coating prepared in presence of SnO2 were reduced compared to the coating without SnO2 and the bare AZ31 substrate, indicating an improvement in the corrosion resistance of the SnO2-doped coating. Keywords: Phosphate coating, Biomaterials, Magnesium alloys, Corrosion, Stannic oxide

The influence of yttrium on the corrosion behavior of Mg–Y alloys has been investigated by electrochemical measurements, scanning electron microscope (SEM) observation, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis in NaCl solution. The corrosion resistance decreased with increasing Y content due to increasing Y-rich zone. The solid-dissolved Y improved the chemical activity of the substrate which promoted the corrosion reaction by forming Y2O3. The corrosion resistance was improved by increasing the Y concentration of matrix and proper net Y-rich structure. The sample has the best corrosion resistance when all the Y element was dissolved into the matrix of Mg–5Y in 0.1 M NaCl. Keywords: Mg–Y alloys, Corrosion behavior, Yttrium element, Solid-dissolved Y

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

This study investigated stress corrosion cracking (SCC) behavior of scratched areas across various depths and stress on alloy 690TT, through precise loading (252 samples in total) and SCC tests. Resultsindicate that SCC mainly initiates at the side walls of the scratch grooves rather than the bottom (sustains the highest stress level), given the low applied load stress about 13% of that at the bottom. Scratch depth is a more significant factor to SCC initiation in scratch groove than loading stress. A probabilistic model was established to predict SCC initiation induced by scratches of varyingdepths.

Hydrogen evolution reaction is inevitable during the corrosion of Mg alloys. The effect of hydrogen on the corrosion behavior of the Mg–2Zn and Mg–5Zn alloys is investigated by charging hydrogen treatment. The surface morphologies of the samples after charging hydrogen were observed using a scanning electron microscopy (SEM) and the corrosion resistance was evaluated by polarization curves. It is found that there are oxide films formed on the surface of the charged hydrogen samples. The low hydrogen evolution rate is helpful to improve the corrosion resistance of Mg alloys, while the high hydrogen evolution rate can increases the defects in the films and further deteriorates their protection ability. Also, the charging hydrogen effect is greatly associated with the microstructure of Mg substrate.

A nano-ZrO2 modified coating system was prepared by incorporation of nano-ZrO2 concentrates into phenolic-epoxy resin. The corrosion performance of the coatings was evaluated in hot mixed acid solution, using electrochemical methods combined with surface characterization, and the effects of nano-ZrO2 content were specially focused on. The results showed that 1% and 3% nano-ZrO2 addition enhanced the corrosion resistance of the coatings, while 5% nano-ZrO2 addition declined it. The coating with 3% nano-ZrO2 presented the minimum amount of species diffusion, the lowest average roughness (5.94 nm), and the highest C/O ratio (4.55) and coating resistance, and it demonstrated the best corrosion performance among the coating specimens.

An analysis architecture is built to make full use of natural environment corrosion of materials data. All environmental factors, such as average temperature, average relative humidity, rainfall hours, sunshine duration, chloride ion settlement, etc., in nine atmospheric test stations, including Beijing, Wuhan, Jiangjin, and Wanning, and seawater temperature, salinity, dissolved oxygen, pH values, etc. in four marine test stations, including Qingdao, Zhoushan, Xiamen, and Yulin, are modelled monthly using a statistical analysis technique. Normal distribution, logarithmic normal distribution, Weibull distribution, and uniform distribution of the samples are checked by the Shapiro-Wilk and Kolmogorov-Smirnov methods. Subsequently, the probability distribution function, the expected population value and variance, and the confidence interval are estimated. Corrosion data for twenty-two kinds of carbon steels, low alloy steels, and stainless steels, including A3, 3C, 16Mn, 10CrMoAl, 1Cr18Ni9Ti, in atmospheric and marine test stations are analyzed. The main environmental factors for atmospheric and marine corrosion of each type of steel are determined by grey relational analysis. Subsequently, a predictive model incorporating the main corrosion environmental factors, exposure time, and corrosion rate is built by the BP artificial neural network. After the evolution of corrosion pit depth is predicted by the artificial neural network, a fracture mechanics calculation is used to evaluate the residual life of a structure with corrosion pit defects.

In this manuscript, we have developed an efficient spraying method to successfully fabricate a series of flower-like coordination polymers (CP) microparticles, including Co/BDC (1,4-benzenedicarboxylate) metal organic frameworks (MOF) and infinite coordination polymers (ICP) microparticles, as well as Ni-Co/BDC MOF and Zn/DOBDC (2,5-dioxido-1,4-benzenedicarboxylate) MOF. The spraying method has shown high efficiency and universality in synthesizing the flower-like CP. The crystalline structure can be adjusted by varying the solvent composition in the spraying process. SEM observation demonstrated the MOF and ICP microparticles possess the similar flower-like structure, which is composed of nanoflakes with smooth surface, and the flower-like microparticles could be monodisperse with as low as 5% polydispersity. Moreover, the fabrication of the flower-like CP microparticles by spraying has a wide operation window, because there is no need to precisely control the experiment conditions, like solvents, concentration, and spray order. Due to the practicality of spray technique, this work would pave the way for the manufacture of the flower-like materials and have great potential in applications of catalysis, sensor, energy storage, and so on.

The inhibition of AA2024-T3 corrosion by the synergistic combination of 3-Amino-1,2,4-triazole-5-thiol (ATAT) and cerium chloride in sodium chloride solution is assessed. Analysis of electrochemical impedance spectroscopy results show improved corrosion inhibition for the inhibitor combination by increased charge transfer resistance. Scanning vibrating electrode techniquewas utilized for corrosion current monitoring and quantification. X-ray photoelectron spectroscopy and time of flight secondary ionmass spectrometry were utilized to characterize the ATAT/Ce based film and to explain the mechanism of inhibition. The obtained results demonstrate a good potential of the inhibitor combination for improved suppression of corrosion processes. [ABSTRACT FROM AUTHOR]

A micro-arc oxidation (MAO) coating was deposited with phytic acid (PA) and tannic acid (TA) on the AZ31 Mg alloy. The surface morphologies and chemical compositions were investigated using field-emission scanning electron microscopy, X-ray photoelectron spectrometry, Fourier transform infrared and X-ray diffractometry. Plate counting method was employed to confirm the antibacterial effect of the TA. The corrosion resistance of the coatingwas measured using electrochemical and hydrogen evolution tests. The results indicated that the thicker TA-MAO coating had smaller pores, no micro-cracks compared to the MAO coating, which possessed a good corrosion resistance and antibacterial activity in Hank's solution. The molecular recognition effect of TA was discussed. TA also could be used as a stabilizing agent of the hydroxyapatite (HA) precipitate during the immersion. Additionally, the corrosion mechanism for the TA-MAO coating was proposed. [ABSTRACT FROM AUTHOR]

Numerical modelling of the effects of different applied load levels on the growth of metastable single pit in stainless steel is the subject of the present work. A cellular automata model integrated with finite element analysis is used, taking into account both the electrochemical reactions during metastable pitting growth process and the real-time influence of local stress/strain distribution at pit surface on anodic dissolution. Specifically, in the current work the impacts of uniaxial load levels on pitting corrosion for various conditions of passive layer degradation extents and hydrogen ions diffusion coefficients are quantitatively assessed in terms of current transient. For a general condition with uniaxial applied load level increases from 0 MPa to 250 MPa, the ascending trend of current transient and current density transient is observed due to the increase of plastic strain accumulation at pit bottom, revealing the enhancement of metastable pit growth rate. Meanwhile, the critical magnitude of load level enabling metastable pitting to alter into the development of stable pit for each condition is discussed and predicted. [ABSTRACT FROM AUTHOR]

A type of self-healing coating for AM60 Mg alloy was prepared by loading interphase inhibitors into micro-arc oxidation (MAO) coating. The effects of inhibitor species, impregnation methods, and MAO status on the self-healing properties of the coatings were studied using electrochemical impedance spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The results showed that, among the three selected inhibitors, Na3PO4 is the most efficient inhibitor as it forms a long-lasting protective product film Mg3(PO4)2 in the scratched areas. In comparison with atmospheric impregnation, vacuum impregnation can efficiently load inhibitors into MAO pores both in quantity and depth. Although the large size of MAO pores is harmful to the corrosion resistance of MAO coating, it is beneficial for the self-healing properties owing to the easy loading of inhibitors. [ABSTRACT FROM AUTHOR]

The influences of glucose and amino acid (L-cysteine) on the degradation of pure magnesium have been investigated using SEM, XRD, Fourier transformed infrared (FTIR), X-ray photoelectron spectroscopy (XPS), polarization and electrochemical impedance spectroscopy and immersion tests. The results demonstrate that both amino acid and glucose inhibit the corrosion of pure magnesium in saline solution, whereas the presence of both amino acid and glucose accelerates the corrosion rate of pure magnesium. This may be due to the formation of -C=N- bonding (a functional group of Schiff bases) between amino acid and glucose, which restricts the formation of the protective Mg(OH)2 precipitates. [ABSTRACT FROM AUTHOR]

The size, distribution, and volume fraction of second phases are altered during extrusion deformation. As a result, the microgalvanic corrosion of Mg alloys will change. The corrosion behaviors of cast and extruded EW75 (Mg-5Y-7Gd-1Nd-0.5Zr) were studied by scanning electron microscopy observations, hydrogen evolution and weight loss measurements, and electrochemical tests. Extruded EW75, which has a lower volume fraction, smaller size, and more uniform distribution of second phases, is found to exhibit better corrosion resistance than cast EW75; the difference can be attributed to weaker microgalvanic corrosion and a more protective surface film. [ABSTRACT FROM AUTHOR]

Based on corrosion fatigue tests using a boat-shaped specimen in borated and lithiated high-temperature water, the corrosion fatigue behavior of Alloy 690 tubes was investigated. An Institute of Metal Research fatigue model for the nickel-based alloys is proposed, which incorporates fatigue life data of Alloy 690 tubes, as well as round-bar specimen data from the open literature. The proposed environmental fatigue life correction factor Fen addresses the effects of temperature, strain rate, and dissolved oxygen concentration. An evaluation methodology for environmental fatigue damage of structural materials in nuclear power plants is proposed. [ABSTRACT FROM AUTHOR]

In order to elucidate the impact of s phase on the oxidation film formation and stress corrosion cracking (SCC) resistance of 316L stainless steel, corrosion, SCC and three-point bending tests were conducted and the microstructures of the s phase in 316L safe-end pipes were characterized via optical microscopy, environmental scanning electron microscopy and scanning Kelvin probe force microscopy. The results indicated that the s phase was detrimental to the SCC resistance of 316L in high temperature and high pressure environments and the existence of inherently hard and brittle s phase could change the cracking mode. [ABSTRACT FROM AUTHOR]

Characteristics of oxide films formed on 304 (UNS S30400) stainless steel during crevice corrosion in 290°C pure water have been investigated. It was found that the oxide films were different at different sites along the crevice. Decreased dissolved oxygen within the crevice resulted in a potential gradient. Such a potential drop affected the development of oxide films. The lamellar oxide near the crevice mouth was mainly FeCr2O4. The regular oxide far from the crevice mouth was mainly Fe3O4. Possible mechanisms of crevice corrosion and growth of the oxide films at different sites in high-temperature water are also discussed. [ABSTRACT FROM AUTHOR]

A window was developed on a high-temperature, high-pressure refreshed autoclave to perform in situ tests. High-purity single crystal sapphire was used as window material to withstand the harsh environment and minimize the production of fluorescence. The cone-shaped internal structure enables a large light flux necessary for the in situ optical observation. Through this window, in situ optical observation and Raman tests were successfully performed in high-temperature, high-pressure water using a long-distance microscope and a custom-made Raman system. The formation of spinel oxide on 304 stainless steel in oxygenated water containing a high concentration of Ni cations was verified by in situ Raman tests. [ABSTRACT FROM AUTHOR]

The microscopic residual stresses beneath scratches on thermally treated (TT) UNS N06690 have been measured using synchrotron radiation x-ray diffraction; the effect of these residual stresses on initiating stress corrosion cracking (SCC) has been studied in 10% sodium hydroxide (NaOH) + 10 g/L lead oxide (PbO) solution at 330°C. Results show that scratching causes local residual tensile stresses parallel to the scratching direction at the scratched surface and local residual compressive stress normal to the scratching direction beneath the scratch. The residual tensile stresses at the scratched surface will act as a precursor of SCC. The residual compressive stresses beneath the scratch cannot stop crack growth of N06690 TT in 10% NaOH + 10 g/L PbO solution at 330°C. [ABSTRACT FROM AUTHOR]

The assembly of Ag nanowires on quartz substrates from suspensions of water and ethylene glycol under stirring has been investigated. The introduction of stirring makes a remarkable difference to the assembly morphology. Firstly, the surface coverage of Ag nanowires is increased by a factor of 4 (in water) and 8 (in ethylene glycol) with stirring. Secondly, the Ag nanowires assembled in the stirred ethylene glycol dispersion were highly aligned. The influence of the surface of substrates, solvents and profile of the nanowires on the alignment has been explored, which indicates that stirring is an efficient way to generate nanowire arrays. This study has revealed the great potential of the stirring-assisted assembly technique in producing structurally controlled nanoarchitectures, opening up new opportunities for manufacturing ordered nanomaterials. [ABSTRACT FROM AUTHOR]

This work mainly investigated the microstructure and mechanical properties of Mg-Zn-Y-Zr alloys with Zn/Y ratios of 5 and 10. An X-ray diffraction (XRD) analysis indicated that the two alloys were mainly composed of an icosahedral phase (I-phase) and α-Mg matrix. For the alloy with a Zn/Y ratio of 10, however, the diffraction peaks of the I-phase were stronger. Microstructure observation showed that the I-phase preferentially existed in the form of I-phase/ α-Mg matrix interdendritic eutectic pockets at grain boundaries. Moreover, when the Zn/Y ratio was increased 2 times, the volume fraction of the I-phase in the α-Mg matrix increased 1.5 times and a tiny Mg7Zn3 phase formed. Energy-dispersive spectroscopy (EDS) mapping and electron probe microanalysis (EPMA) results suggested that the chemical composition of the I-phase was not a constant value. Computer-aided cooling curve analysis (CA-CCA) indicated that, for the alloy with a Zn/Y ratio of 5, formation of the I-phase relied on the W-phase transformation and the eutectic reaction of the residual melt. However, the I-phase formation for the alloy with a Zn/Y ratio of 10 depended on the eutectic reaction of the melt. Tensile tests indicated that the mechanical properties of the two as-cast alloys were poor. After hot extrusion processing, the mechanical properties of the alloy with a Zn/Y ratio of 10 were noticeably increased. The ultimate tensile strength (UTS) and elongation to failure reached 320 MPa and 13 pct, respectively. [ABSTRACT FROM AUTHOR]

The aim of the study is the development of an intumescent nanocomposite coating to provide fire protection for the metallic substrate. Acrylic nanocomposites containing nanoclay and relative intumescent nanocoatings are prepared. The effect of nanoclay on the thermal degradation of an intumescent nanocomposite coating is analyzed by using differential thermal analysis, thermogravimetry, and X‐ray diffraction. The influence of the added content of nanoclay on fire performance is studied by a fire protection test and measurements of the limiting oxygen index and effective thermal conductivity. The distribution of nanoparticles in the acrylic nanocomposite is characterized by transmission electron microscopy. The flame‐retardant efficiency of the intumescent nanocomposite coating is improved by 1.5% well‐distributed nanoclay particles. However, 3% nanoclay produces a negative effect on the fire performance of the coating. Fire protection tests and scanning electron microscopy observations reveal that the fire‐retardant property of a conventional intumescent coating is destroyed by aging, whereas the nanocomposite coating modified with 1.5% nanoclay demonstrates good aging and fire resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1681–1689, 2007 [ABSTRACT FROM AUTHOR]

Abstract  The cooperation of pH, temperature and Cl− concentration on electrochemical behavior of NiTi shape memory alloy in artificial saliva was studied using orthogonal test method. The results showed that the pitting potential for NiTi in artificial saliva decreased at low and high pH; at 25∘C, the pitting potential was the lowest compared to those at 10∘C, 37∘C and 50∘C; when the Cl− concentration was not less than 0.05 mol/L the pitting potential decreased with the increase of Cl− concentration. The free corrosion potential of austenitic NiTi was lower than that of mixture of austenite and martensite. [ABSTRACT FROM AUTHOR]

The effect of hydrogen on the stress corrosion cracking (SCC) for X-70A and X-70B pipeline steels in near-neutral pH environments was studied by monotonic tensile tests on slow strain rate tests (SSRT) machine and cyclic tests on SSRT machine and fatigue machine. The results showed that SCC intensity increased at high cathodic protection potential. Hydrogen charged at high pressure enhanced SCC sensitivity. Cyclic tests under elastic strain condition could not take the specimens to fracture and the hydrogen content was very low. However, when the load was raised to produce plastic deformation, the specimens failed within limited time and there was brittle fracture appeared on the fracture surface. Moreover, the hydrogen content was higher than that under elastic strain condition. The SCC mechanism of X-70A and X-70B pipeline steels in near-neutral pH environments was related to hydrogen accumulation induced by plastic strain. [ABSTRACT FROM AUTHOR]

Slow strain rate tests (SSRT) and environmental scanning electron microscopy (ESEM) were utilized to investigate stress corrosion cracking (SCC) behavior of electropulsed POSCO and Bao Steel X-70 pipeline steels specimens in XJ solution purged with 5% CO2 + 95% N2 at the strain rate of 2E-6/s. The results showed that the ultimate tensile strengths (UTS) were raised considerably for the electropulsed specimens. The UTS for electropulsed POSCO X-70 pipeline steel was enhanced much more compared to electropulsed Bao Steel X-70 pipeline steel. In addition, the relationship among UTS, the original grain size and high voltage in electropulsing treatment was revealed. SCC sensitivity increased with the decreasing electrochemical potential, especially at high cathodic potential. [ABSTRACT FROM AUTHOR]

In this article, the authors discuss various articles on stress corrosion cracking, advances in corrosion resistant materials and the role of atomic hydrogen in hydrogen embrittlement published in this issue of the periodical.

During the deformation of Mg alloys, {10-12} extension twin, as one of the most active deformation mechanisms, contributed much to the formation of basal texture, yet little to dynamic recrystallization (DRX) grains, i.e., effective grain refinement. In this work, {10-12} extension twin had been creatively utilized to achieve grain refinement and property improvement in a Mg-Gd-Y alloy by multi-directional impact forging (MDIF). Firstly, flourishing {10-12} extension twins divided the parent grain into many fine independent regions (~10 μm). Meanwhile, a large number of twin boundaries were pinning mainly by interaction with neighboring dislocations in twin or matrix. Secondly, those pinned twin boundaries can effectively accumulate dislocation slips and promote the formation of extensive low angle grain boundaries (LAGBs). These high densities of LAGBs can further subdivide the independent regions provided by extension twins into micro-regions (~5 μm). Thirdly, those fine micro-regions developed to be DRX after a dynamic recovery. Finally, we obtained a yield isotropy high-strength Mg alloy with an ultimate tensile strength of 354 MPa after MDIF of 110 passes. This work proposed a brand new insight to prepare wrought Mg alloy with fine grain, yet without strong texture, which is beneficial to better formability and mechanical property isotropy.