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In this study, magnetron sputtered carbothermic reduced iron boride (FeB) coatings were developed on grey cast iron (GCI) substrates at different substrate temperatures. The impact of substrate temperature on structural, mechanical, and corrosion behavior was examined for two FeB deposition scenarios: FeB coatings deposited at room temperature (RT) and at 500 °C substrate temperature. The evolution of phases and microstructure was studied using XRD and FESEM, respectively. The mechanical properties, creep, deformation behavior, and adhesion strength (scratch test) of the deposited coatings were investigated using nanoindentation at ambient temperature. The highest hardness and Young's modulus of 16 GPa and 231 GPa respectively, were achieved at 500 °C due to microstructural enhancement. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion behavior of the coatings. The results show that substrate temperature strongly influences the surface morphology of the coatings, which in turn governs the mechanical and corrosion behavior of the FeB coating. The FeB-coated GCI at 500 °C substrate temperature showed higher resistance to scratching, better mechanical properties, and improved corrosion resistance which is attributed to the enhanced adhesive strength, refined microstructure, and formation of protective oxide layers of FeB on the surface of the coatings. [Display omitted] • FeB coatings have a hardness of 11.8 GPa, an elastic modulus of 165 GPa at RT, and 15.6 GPa and 231 GPa at 500 °C. • The FeB coating showed conformal cracking at RT and tensile cracking at 500 °C, indicating better adherence at 500 °C. • At 500 °C, the FeB coating displayed improved corrosion resistance and reduced corrosion current density. • EIS data revealed higher charge transfer resistance and a larger semicircle arc for the FeB coating at 500 °C compared to RT. [ABSTRACT FROM AUTHOR]

The corrosion resistance and passivation property of CoCrNi MEA in NaCl solution containing various concentrations of NaHSO3 were systematically investigated. The results reveal that the presence of HSO3− increases defects within the passive film, thins its thickness and disrupts the stability and integrity of the film. Increasing HSO3− concentration reduces the passivity of the MEA, facilitates the nucleation of metastable pitting and increases the tendency of metastable pitting to evolve into stable pitting, as well the corrosion rate increases significantly. Moreover, the corrosion of the MEA is aggravated by the micro-galvanic corrosion cells constituted between the substrate and the oxide inclusion. In addition, the MEA suffers a significant selective dissolution. [ABSTRACT FROM AUTHOR]

Recycling's value in conserving scarce resources, avoiding environmental damage to the land, and reducing energy consumption is well known. This research aims to develop a composite that uses recycled reinforcement that was formed through an in situ method to build confidence in the usage of recycled materials. Thus, in connection with defense and aerospace industry applications, aluminum composite alloys receive more interest due to their light weight and high strength with improved mechanical properties; therefore, this research focuses on the fabrication of in situ-developed recycled TiC (r-TiC)-reinforced AlZnMgCu composites, i.e., new recycled materials. Experiments were conducted to determine the synthesized composites' microstructural, mechanical, tribological, and corrosion properties. The microstructural study showed that r-TiC was distributed uniformly along the grain boundaries until the addition of 12% r-TiC. However, the accumulation of reinforcements began at 14% r-TiC addition and became more aggregated with subsequent increases in the percentage addition of r-TiC. The mechanical and tribological tests showed that the composite with 14% r-TiC was superior to all other compositions, with 60% improved mechanical qualities and the lowest wear rate of 0.0007 mm3/m. Composites containing 2% r-TiC showed the best corrosion resistance, an increase of 22% over AlZnMgCu, without reinforcement. [ABSTRACT FROM AUTHOR]

Corrosion of steel bars embedded in reinforced concrete structures considerably reduces the service life and even causes early failure of the structure. This paper investigates the early corrosion behavior of an alloy corrosion-resistant steel bar in seawater–sea sand concrete (SWSSC) using various electrochemical measurements [electrochemical impedance spectroscopy (EIS) linear polarization resistance (LPR)] and surface characterization techniques [scanning electron microscope-energy dispersive spectroscopy (SEM-EDS), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS)], in comparison to low carbon steel bar (LC) and stainless steel bar (SS). The results reveal that the Cr10Mo1 alloy corrosion-resistant steel bar (CR) in SWSSC shows significant increase in the radius of the capacitive arc in later stages, particularly in the low frequency region. This increase in CR can be attributed to the enhanced corrosion resistance of the passivation film, as well as the rise of impedance at the interface between the passivation film and the concrete matrix. These improvements have effectively inhibited the penetration of free chloride ions into the concrete, thereby impeding the initiation and propagation of corrosion in CR In addition, the mechanical properties, pore structure and the hydration production of SWSSC were investigated. Based on the interactions between steel substrate and concrete matrix, the possible resistance mechanism of CR was proposed. This study innovatively provides a comprehensive evaluation of the effectiveness of CR in SWSSC. [ABSTRACT FROM AUTHOR]

In historical reinforced concrete buildings, square ribbed rebars, round ribbed rebars and square twisted rebars are the main steel rebars. In order to determine the corrosion behavior of such historical steel rebars, we investigated the deterioration mechanisms of steel rebars in historical architecture in simulated concrete pore solution using various electrochemical tests and microscopic examination of corrosion products. The hot-rolled ribbed bar (HRB)335 rebars used in modern buildings were used as a control sample. The results demonstrated that the corrosion process of the historical rebars was similar to that of HRB335 rebars. Nevertheless, there were some differences in the chemical composition, microstructure, passive film characteristics, critical chloride ion concentration, and corrosion products. In the passivation stage, the stability order of the passive film generated on the surface of the rebars was as follows: square ribbed rebars > square twisted rebars > HRB335 rebars > round ribbed rebars. In the Cl− corrosion stage, the damaging effect order of Cl− on the passive film is square ribbed rebars > HRB335 rebars > square twisted rebars > round ribbed rebars. The critical chloride ion concentration was between 0.5% and 2.0% by weight. The corrosion products were mainly Fe2O3 , α -FeOOH, γ -FeOOH. β -FeOOH, and protective Fe3O4. The corrosion products of HRB335 rebars were mainly nonprotective crystallized FeOOH with various morphologies. The results of this study provide a scientific foundation for the conservation design and residual life prediction of historic reinforced concrete buildings. [ABSTRACT FROM AUTHOR]

A liquid-repellent and corrosion resistant surface was fabricated on AZ31B Mg alloy by the usage of CeO 2 and TiO 2 nanoparticles (NPs), plasma electrolyte oxidation (PEO) method, and subsequent surface modification. The whole process included two main steps: a) applying PEO with CeO 2 –TiO 2 NPs on AZ31B and b) decreasing surface energy by using a fluorinating agent. Elements that were present on the surface were investigated by XRD and EDS analyses. Surface morphology and its roughness were scrutinized by FESEM images and AFM tests, respectively. Contact angles (CA) of water and some oils (Ethylene glycerol and Glycerol) on the prepared surface were measured. CAs of water and ethylene glycerol were reported at 175.6° and 151.4°, respectively. Also, the corrosion behavior of the prepared surface was assessed by EIS and potentiodynamic polarization analyses. Results showed that the corrosion rate of the neat AZ31B decreased noticeably from 127.78 to 0.027 mpy for superamphiphobic PEO-NPs AZ31B. The prepared sample showed high mechanical durability, which was scrutinized by water floatation, abrasive with grit SiC paper, adhesive tape peeling, and bending tests. After immersion of the sample in 5 wt% NaCl solution for various hours, results showed that the prepared sample had a noticeable corrosion resistance stability. [Display omitted] • A durable superamphiphobic surface was fabricated on AZ31B. • The prepared surface showed a remarkable water and oil repellency. • A prepared superamphiphobic surface promoted noticeably the corrosion resistance of AZ31B. • A superamphiphobic surface showed brilliant corrosion resistance stability and mechanical durability. [ABSTRACT FROM AUTHOR]

High-strength aluminum alloys have been widely used in aviation, aerospace and other industries because of their high specific strength and good machining property. Corrosion is an important factor affecting the safety and stability of high-strength aluminum alloys in service. Based on the preparation process of high-strength aluminum alloys, this paper focuses on the effect of structural evolution caused by heat treatment on the corrosion property of high-strength aluminum alloys. The corresponding relationship between the micro structure and corrosion behavior of high-strength aluminum alloys is analyzed. Research directions for improving the corrosion property of high-strength aluminum alloys are proposed. The segregation of elements and phases in high-strength aluminum alloys can easily lead to electrochemical inhomogeneity of microstructure, causing corrosion of substrate. Therefore, based on the optimization of composition, the melt casting process, deformation process and heat treatment process of high-strength aluminum alloys should be regulated to prepare the microstructure with uniform distribution of elements and second phases, and uniform electrochemical property, which is crucial for improving the corrosion property of high-strength aluminum alloys. In addition, the corrosion sensitivity of alloys is affected by the width of the precipitate free zone and the distance and distribution of the grain boundary precipitation phases of alloy. Thoroughly studying and clarifying the effect of various structures such as precipitate free zone on the corrosion behavior of alloys is the prerequisite for the preparation of high-strength aluminum alloys with high corrosion property. To balance the mechanical property and corrosion property of high-strength aluminum alloys, heat treatment methods such as aging and thermomechanical treatment should be optimized, and new composite heat treatment methods should be developed. Meanwhile, the test methods and evaluation methods for the corrosion property of high-strength aluminum alloys are discussed. In order to more efficiently and accurately evaluate the corrosion property and service safety of high-strength aluminum alloys, further research work should be carried out in the combined use of traditional evaluation methods with modern data processing technologies such as digital twin, virtual simulation and machine learning. [ABSTRACT FROM AUTHOR]

In this study, Al 2 O 3 –20TiO 2 (AT) and Cr 2 O 3 –3TiO 2 –5SiO 2 (CT) coatings were prepared by atmospheric plasma spraying (APS), The microstructure, phase compositions and corrosion behavior were studied comparatively. The results indicated that both coatings had layered structure, with an average surface roughness RA around 6 μm, an adhesive strength around 35 MPa, and a porosity around 4 %. The AT coating mainly composed of γ-Al 2 O 3 and α-Al 2 O 3 , and the CT coating composed Cr 2 O 3 respectively. Moreover, the AT coating exhibited better corrosion resistance than the CT coating. In artificial seawater, the corrosion process was strongly related to the porosity. The corrosion rate (based on the corrosion current density) of the two coatings showed a same trend which decreased first and then increased. It was thought that the blocking of early corrosion products in holes was helpful to delaying the progress of corrosion. In contrast, the later corrosion products would promote the formation and propagation of cracks, accelerating the corrosion. In the simulated environment with high pressure and hydrogen sulfide seawater, the corrosion process was strongly related to the porosity as well as the brittleness of the coatings. The corrosion rate (based on the weight loss) of the AT coatings still remained the same trend as it in the artificial seawater. However, the CT coating showed a continuously increasing corrosion rate, due to higher porosity and brittleness resulted in a large number of cracks under external stress, which offered corrosion channels. [ABSTRACT FROM AUTHOR]

The effect of 10 wt% alumina, 20 wt% (10Al 2 O 3 -10MoS 2), and 30 wt% (10Al 2 O 3 -10MoS 2 -10Ag) reinforcements on the tribological and corrosion properties of copper was investigated. The nanocomposites were prepared by the ball milling coating method and then fabricated by the cold and hot compaction technique. The copper's hardness increased gradually from 96 HV to 227 HV for the 30 wt% (Al 2 O 3 -MoS 2 -Ag) representing an increase of 136.48 %. Adding 30 wt% (Al 2 O 3 -MoS 2 -Ag) to the copper reduced the wear rate from 22 mg/min to 0.3 mg/min under 50 N applied load, owing to the presence of two types of self-lubricating materials, MoS 2 and Ag. This nanocomposite recorded the lowest mean coefficient of friction of 0.166 compared with 0.23 for copper. Adding the alumina increased the copper corrosion rate to 3.83 mm/year due to increased oxidation ratio that facilitates the penetration of the electrolyte. However, the Cu/(Al 2 O 3 -MoS 2 -Ag) sample recorded corrosion rates of 0.467 mm/year compared with 0.446 mm/year for copper. [ABSTRACT FROM AUTHOR]

• The paper provides a detailed review of different methodologies for analyzing Mg corrosion, including electrochemical, non-electrochemical, and analytical techniques. • A diverse set of analytical tools is used in Mg corrosion research to explore the interplay between corrosion, microstructure, and material dissolution mechanisms. • Tools like SEM/EDS, SKPFM, and TEM offer site-specific analysis, while XPS, FTIR, and BIB provide a more general view of the specimen surfaces. • Instruments such as TKD, AES, and ToF-SIMS/NanoSIMS are specialized for surface layer analysis, contrasting with CT tomography and SEM that reveal details from within the specimen. • Increasing significance of in-situ analysis in Mg corrosion research is highlighted, enabling the real-time observation of corrosion processes and the identification of initial corrosion products as they emerge. Corrosion is a pervasive phenomenon affecting materials across a multitude of scales, from the atomic to the macroscopic. This review paper presents a comprehensive examination of the methodologies employed in the analysis of magnesium corrosion, including electrochemical, non-electrochemical and analytical approaches, emphasizing the need for a diverse array of analytical tools to understand the complex interplay between corrosion, microstructure, and the dissolution mechanisms of magnesium alloys. The research showcases the utility of specific tools like SEM/EDS and SKPFM for targeted site analysis, while XPS and FTIR provide a broader perspective on specimen surfaces. The paper also discusses the value of in-situ analysis techniques, which allow for the real-time observation of corrosion processes, offering a dynamic view of the emergence and evolution of corrosion products. These in-situ methods stand in contrast to ex-situ analyses, which only permit post-experimental evaluation. By highlighting the capabilities of various analytical tools, from those that reveal surface layer details to those that probe deeper structures, and from those that detect primary elements to those that trace minute quantities of impurities, this study underscores the intricate nature of corrosion and the critical role of advanced analytical techniques in fostering a deeper understanding of material degradation. The findings advocate for the increased application of in-situ analysis in magnesium corrosion research, as it provides a more immediate and accurate depiction of corrosion dynamics, potentially leading to more effective corrosion prevention and control strategies. [Display omitted] [ABSTRACT FROM AUTHOR]

Galvanic corrosion behavior of AZ91D alloy / 45 steel couple in 3.5 wt.% NaCl solution under 0, 0.2 and 0.4 T magnetic field were studied by microstructure observation, immersion test and electrochemical measurement. The mixed potential theory was used to estimate the galvanic current density and the mixed potential of the galvanic corrosion between AZ91D alloy and 45 steel. The results indicated that magnetic field could accelerate the corrosion of AZ91D alloy, and impede the corrosion process of 45 steel. The effect of magnetic field on corrosion sensibility and corrosion rate of these two alloys increased as the intensity rising. The galvanic corrosion rate of the couple was accelerated by magnetic field. With the magnetic field intensity rising, the galvanic corrosion sensibility and corrosion rate of the couple increased. The effects of magnetic field on the galvanic corrosion performance of the couple and the corrosion behavior of AZ91D alloy and 45 steel were due to the appearance of field gradient force and magnetohydrodynamic (MHD) force. The mixed potential theory has a certain accuracy to estimate the E couple and i couple values in this work. [ABSTRACT FROM AUTHOR]

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Wire arc additive manufacturing (WAAM) has garnered significant attention in industries owing to its ability to produce complex geometrical components with lower production costs. In the present work, WAAM process was used to fabricate rectangular plates and cylindrical tubes from ER70S6 filler material based on the cold metal transfer technique. The microstructure of the rectangular plate was investigated at three different locations, viz., top, middle and bottom regions along the build direction (BD). It was characterized by the presence of ferrite and pearlite phases along with Mn and Fe rich carbide precipitates. The average grain size of the middle location was found to be marginally higher as compared to the other two locations which resulted into lower hardness in the former. The tensile properties were evaluated for three directions, i.e., 0°, 45° and 90° with respect to BD. The total elongation and strength were found to be slightly higher for the specimen deformed 90° with respect to BD. Furthermore, the performance of the additive manufactured components was analyzed through corrosion and compression tests. The corrosion current density and corrosion rate were found to be higher for the middle location as compared to the top and bottom locations owing to its higher pearlite fraction. The compression of tubes was carried out under axial and transverse loading conditions. Axisymmetric progressive folding of the tubes was observed under axial loading, whereas infinity shape formation was witnessed under transverse loading. The above deformation modes indicated the uniformity in mechanical properties of WAAM tubes without any discontinuity, and further suggested that these tubes could act as excellent energy absorbers. [ABSTRACT FROM AUTHOR]

This study investigated the effect of severe plastic deformation induced by friction stir back extrusion on microstructure, mechanical properties, and corrosion resistance of Al-Cu-Mg alloy containing 0.5 wt.% of lithium micro-alloy and Cu/Mg ratio of 3.8. The effect of the rotational speed of friction stir back extrusion in the range of 600-1200 rpm in the constant traverse speed of 20 mm/min was studied. The results show that the size of equiaxed grains formed during the friction stir back extrusion process due to dynamic recrystallization increases from 21.0 ± 2.3 to 29.6 ± 4.5 μm by enhancing rotational speed from 800 to 1200 rpm. The dominance of the temperature effect on the plastic strain on the surface of wires during the friction stir back extrusion process results in the formation of coarser grains at the surface of wires. Friction stir back extrusion by a rotational speed of 800 rpm and a traverse speed of 20 mm/min result in the maximum yield, tensile strength, and minimum corrosion rate of 353.56 ± 10.31, 509.91 ± 11.56 MPa, and 0.008 mm/year, respectively. The friction stir back extrusion process has increased at least 23, 39, and 29% in yield strength, ultimate tensile strength, and elongation compared to as-cast alloy. [ABSTRACT FROM AUTHOR]

The influence of pre-tensile deformation at different directions on the corrosion properties of AZ31 rolled sheet has been investigated. Uniaxial tensile test with the strain of 6% has been carried out at angles of 0°, 15°, 30°, 45°, 60°, 75° and 90° with rolling direction (RD), respectively. The corrosion behavior of specimens with different deformation directions in 3.5% NaCl solution and 8.5% Na2SO4 solution was measured by immersion test, potentiodynamic polarization method and electrochemical impedance spectroscopy. After immersion tests, the surface characteristics of various specimens were investigated by scanning electron microscope (SEM). Results showed that the tensile directions had a significant influence on the corrosion behavior. With the increase of the angle between tensile direction and RD, the hydrogen evolution rate in the 3.5% NaCl increased first and then decreased. The turning point was A45 specimen with the minimum value of 2.1 mm/y. The similar trends were also observed in the 8.5% Na2SO4 solution. In electrochemical testing, the A45 specimen exhibited the best corrosion resistance with the largest diameter of the impedance arc and lowest self-corrosion current. The further the angle of the specimen deviated from 45° direction, the lower corrosion resistance. [ABSTRACT FROM AUTHOR]

To improve the corrosion resistance and wide the application of Al alloy sheet in the engineering production, a corrosion potential gradient along the thickness of the Al alloy sheet was fabricated using the sprayed Zn layer. The process of arc spraying was employed to obtain the Zn coating with optimizing the parameters. Electrochemical testing was conducted on the surface of Al alloy sprayed with Zn layers at different depths. As the depth in the thickness direction increases, the content of Zn alloy elements gradually decreases and the potential gradually increases. This exhibits a gradual decrease in corrosion tendency. The results of electrochemical impedance spectra (EIS) revealed the existence of pitting corrosion on the surface of the Al alloy. This even extended to the underlying substrate material. In contrast, the Zn coating, when exposed to a corrosive environment, demonstrated the beneficial cathodic effect as a sacrificial anode and the protective function of a passivating film, thus mitigating corrosion. The gradual increase in charge transfer resistance in the impedance spectrum suggested that the corrosion resistance of the sample is increasingly improved. Therefore, it exhibited remarkable resistance to corrosion. Additionally, the SEM surface morphology and XRD pattern were utilized to further explain the corrosion mechanism of the arc-sprayed Zn coating. The Zn coating can provide sacrificial protection to the Al layer due to its higher negative potential and localized corrosion reactivity. This is attributed to the micro-galvanic couples formed between the Zn and Al layer, thus increasing the corrosion resistance of the sheets.

Q345B/2205 dissimilar steel multi-layer multi-pass welded joints were prepared using gas metal arc welding (GMAW). The effects of heat inputs on the microstructures and properties of welded joints were studied. The morphology and composition distribution of Q345B base metal near the fusion line were investigated. The results showed that the welded joints under different heat inputs were all present “carbon depleted zone” and “carburized zones” on both sides of the Q345B base metal and transition layer interface. The microstructure of the “carburized zones” was composed of martensite phase and granular bainite phase. It was found that only the welded joints with heat inputs of 1.765 kJ/mm and 2.860 kJ/mm met the usage requirements. The corrosion behavior and characteristics of the welded joint with a heat input of 1.765 kJ/mm in a 3.5 wt % NaCl solution were investigated intensively. During the soaked process of 14 days, the total impedance value of the welded joint showed first increasing and then decreasing. The maximum value of 8.7 kΩ cm2 was obtained on the 5th day. As the soaked time increased, the corrosion products of the welded joint underwent the formation, thickening, cracking and detachment, which was the main reason of the change in the corrosion resistance. The research results of this article have significant implications for the application of low-alloy steel and stainless steel welded joints in engineering.

High entropy alloys (HEAs) were prepared using a vacuum arc melting method. The effect of Mo partially substituting Ni on the crystal structure and corrosion behaviors was studied. The results show that the HEAs exhibited a multiphase complex crystal structure which was composed of a BCC matrix and several intermetallic phases. The HEAs showed good corrosion resistance despite multiphase heterogeneity. But cyclic polarization showed that the HEAs were susceptible to pitting corrosion. Selective corrosion of Cr-depleted phases after polarization tests was attributed to the galvanic corrosion between Cr-depleted and Cr-rich phases. The spontaneous passive films on the HEAs surface were characterized by p-type semiconductor. Existence of Mo element of the HEAs accelerated passivation reaction kinetics, improved the stability of passive film, accordingly, acquired better general and pitting corrosion resistance.

In this study, 316L stainless steel Laser Powder Bed Fusion (LPBF) samples were manufactured under three different building orientations (0°, 45°, and 90°). Mechanical, microstructural, tribological and corrosion resistance properties were analyzed for all samples. The results demonstrate that the build orientation significantly influences the microstructure, resulting in variations in grain size, texture and defect distribution. Specifically, 0° (Horizontal) samples exhibited excellent mechanical properties, including ultimate tensile strength of 784 MPa and a hardness of 292 HV, while the vertical (90°) samples showed enhanced wear resistance, characterized by reduction in the coefficient of friction. Corrosion resistance was found to be highest in the 0° samples, with a corrosion current density of 0.650 μA/cm2, compared to 1.580 μA/cm2 in the 90° samples. The results from this study show the non-linear effects of build orientation for certain properties and indicates that individual studies are not sufficient to predict the performance of LPBF parts. Therefore, combined studies are required for orientation-based optimization of the mechanical, tribological and corrosion properties of LPBF parts. This study offers valuable insights into the relationship between build orientation and material properties, providing a pathway to tailor the properties of LPBF parts for specific applications.

Most research on the corrosive CoCrFeNi high-entropy alloy (HEA) has mainly modulated element species and atomic concentration recently. However, the corrosive resistance of the passive film in the elevated temperatures environment inevitably need to be extensively explored for application. In this work, the microstructure and corrosion behavior in the elevated temperatures of face-centered cubic (FCC) CoCrFeNiWx (x = 0 and 0.2) HEAs are investigated. The mechanism of passivation layers on the corrosion behavior of HEAs is further discussed for comparison to the alloy of addition tungsten. Through potentiodynamic polarization curves in 3.5 wt% NaCl solution from 25 °C to 70 °C, the addition of tungsten can raise the critical pitting temperature, while maintaining a lower passivation current density and a larger passivation range at the same time. The high resolution X-ray photoelectron spectrometer (HRXPS), electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) are all conducted to analyze the passivation composition and chemical reaction of the present alloys detailly. The CoCrFeNiW0.2 HEA exhibits the uniform Cr2O3 layer on the FCC matrix; the proportion of dispersive WO3 layer on the μ phase precipitates form a double-layer passive film under elevated temperature in 3.5 wt% NaCl. It shows that the synergistic effect of the double-layer passive film significantly enhances the pitting and corrosive resistance in this HEA.

Abstract This study investigates the formation of duplex electroless Ni-P/Ni-B and Ni-P/Ni-B-W alloys through electroless plating process coatings on mild steel using hypophosphite and sodium borohydride as a reducing agent, employing heat-treated. Electroless plating is affordable and suitable for coating convoluted structures. Duplex electroless on mild steel was characterized by X-ray diffraction (XRD), Energy-dispersive X-ray spectrometry (EDS), scanning electron microscopy (SEM) were used to examine the surface and cross-sectional morphologies of the duplex coating, and finally study electrochemical corrosion properties. The analysis reveals that duplex coating yields a thicker, more homogeneous coating with a characteristic cauliflower morphology and spherical nodular structures. The coating was initially amorphous, but finally crystallized when heated to 400 °C. More corrosion resistance was found in the Ni-P/Ni-B and Ni-P/Ni-B-W layers when Ni-B served as the outer covering. This study focuses on the important effects of varying tungsten concentrations and heat treatment on the corrosion resistance, surface quality, and microstructural characteristics of duplex coatings. Showed improved corrosion resistance when exposed to 0.5 g/L of Na2WO4.

Galvanic corrosion behavior of AZ91D alloy / 45 steel couple in 3.5 wt.% NaCl solution under 0, 0.2 and 0.4 T magnetic field were studied by microstructure observation, immersion test and electrochemical measurement. The mixed potential theory was used to estimate the galvanic current density and the mixed potential of the galvanic corrosion between AZ91D alloy and 45 steel. The results indicated that magnetic field could accelerate the corrosion of AZ91D alloy, and impede the corrosion process of 45 steel. The effect of magnetic field on corrosion sensibility and corrosion rate of these two alloys increased as the intensity rising. The galvanic corrosion rate of the couple was accelerated by magnetic field. With the magnetic field intensity rising, the galvanic corrosion sensibility and corrosion rate of the couple increased. The effects of magnetic field on the galvanic corrosion performance of the couple and the corrosion behavior of AZ91D alloy and 45 steel were due to the appearance of field gradient force and magnetohydrodynamic (MHD) force. The mixed potential theory has a certain accuracy to estimate the Ecouple and icouple values in this work.

Corrosion is a pervasive phenomenon affecting materials across a multitude of scales, from the atomic to the macroscopic. This review paper presents a comprehensive examination of the methodologies employed in the analysis of magnesium corrosion, including electrochemical, non-electrochemical and analytical approaches, emphasizing the need for a diverse array of analytical tools to understand the complex interplay between corrosion, microstructure, and the dissolution mechanisms of magnesium alloys. The research showcases the utility of specific tools like SEM/EDS and SKPFM for targeted site analysis, while XPS and FTIR provide a broader perspective on specimen surfaces. The paper also discusses the value of in-situ analysis techniques, which allow for the real-time observation of corrosion processes, offering a dynamic view of the emergence and evolution of corrosion products. These in-situ methods stand in contrast to ex-situ analyses, which only permit post-experimental evaluation. By highlighting the capabilities of various analytical tools, from those that reveal surface layer details to those that probe deeper structures, and from those that detect primary elements to those that trace minute quantities of impurities, this study underscores the intricate nature of corrosion and the critical role of advanced analytical techniques in fostering a deeper understanding of material degradation. The findings advocate for the increased application of in-situ analysis in magnesium corrosion research, as it provides a more immediate and accurate depiction of corrosion dynamics, potentially leading to more effective corrosion prevention and control strategies.

Pure Mg has advantages of low density， good shock absorption performance and good biocompatibility， but its strength is low. Alloying is an important method to modify microstructure and properties of pure Mg. Sn has characteristics of low melting point， high eutectic temperature with Mg， high solid solubility in Mg， stable chemical properties and large output， which is appropriate to be an alloying element. The effects of alloying element Sn on microstructures and properties of Mg alloys were reviewed in this paper. Sn enriches at the front of the solid-liquid interface， dissolves in Mg matrix， reduces the ratio of critical resolved shear stress value of the pyramidal plane to that of the basal plane， and elevates the electric potential of Mg matrix. Mg2Sn precipitates can hinder dislocation and grain boundary movement， and form galvanic corrosion cells with Mg matrix. Therefore， effects of Sn addition include grain refinement， age hardening and strengthening， improving plasticity， accelerating or reducing corrosion rate， enhancing discharge efficiency and discharge potential. At present， the main problems restricting the development of Mg-Sn alloys are slow aging， low hardness and strength. In the future， endeavors should be made to develop rapidly age-hardenable Mg-Sn alloys with high strengths， wrought Sn-containing Mg alloys with good ductility， and Sn-containing structural-functional Mg alloys.

Monolayer (TiN/Ti) and multilayer films (TiN/Ti; CrN/Ti, TiN/CrN/Ti) with an average thickness of 2300 nm were deposited on SS304 steel using the cathodic arc deposition method. Analysis revealed the presence of numerous macroparticles (peaks) and pinholes (valleys) uniformly distributed across the surface. The monolayer film exhibited superior surface quality compared to the multilayer films but demonstrated poor adhesion to the substrate. X-ray diffraction spectroscopy detected a noticeable shift in the preferred orientation of the deposited film, transitioning from (111) to (200) when employing a multilayer structure. Applying ceramic coatings onto stainless steel induced significant alterations in the potentiodynamic polarization curves of monolayer and multilayer films, resulting in a shift towards more noble potentials and lower corrosion currents than the substrate. Furthermore, the potential passive range expanded when employing multilayer structures based on TiN and CrN.

In the present work, a wall-structured nickel-aluminum bronze (NAB) alloy was fabricated via electron beam directed energy deposition (EB-DED) additive manufacturing with a single-pass multi-layer deposition strategy. A comprehensive comparative analysis of microstructure, mechanical properties, and corrosion resistance was conducted against a conventionally cast NAB alloy. The inherent rapid solidification and cyclic thermal processing of the EB-DED technique profoundly influenced the microstructural evolution of the NAB alloy. The as-deposited NAB alloy exhibited a fine-grained microstructure, devoid of the martensitic β′ phase, accompanied by the spheroidization of partial κIII precipitates, and a homogeneous distribution of alloying elements. These distinctive microstructural attributes synergistically enhanced the strength, hardness, and toughness of the NAB alloy, conferring superior mechanical properties compared to its cast counterpart. Furthermore, the as-deposited alloy demonstrated remarkable corrosion resistance in a 3.5 wt% NaCl solution, significantly outperforming the cast alloy. The underlying mechanisms governing the structure-property relationships were elucidated. This comprehensive investigation provided insights into the unique characteristics and potential applications of EB-DED fabricated NAB alloys, positioning them as promising candidates for high-performance components subjected to severe mechanical and corrosive service conditions.

In order to create a cost-effective Zr alloy with superior overall characteristics, Zr-xFe (x = 0, 2, 4, 6, 8, 10 at.%) binary alloys were prepared by a vacuum arc furnace system. The microstructure of these alloys was examined utilizing various techniques such as optical microscope, X-ray diffractometer, scanning electron microscopy, and transmission electron microscopy. The results showed that the addition of Fe effectively refined α-Zr slats, and the Zr3Fe compound phase was dispersed throughout the alloy. However, the composition line of the alloying elements in the phase diagram intersected with the Zr2Fe and β-Zr eutectic lines when the Fe content exceeded 6 at.%. Zr–Fe alloys were transformed from monocrystalline-eutectoid to eutectic-eutectoid reactions. The Zr3Fe compound phase accumulated inside the grain and at the grain boundary as a result of the eutectic reaction, which stabilized the microstructure of the Zr–Fe alloys. This seriously affected the mechanical and corrosion properties of the alloys. The mechanical and corrosion properties of the alloys were assessed by universal testing machine, dynamic microhardness tester, Vickers hardness tester, and electrochemical workstation. The mechanical and corrosion properties of Zr–2Fe were excellent due to the coupling effect of Zr3Fe and grain refinement. The surface of the Zr–Fe alloy was analyzed by X-ray photoelectron spectroscopy, revealing the presence of passivation film components ZrO2 and Fe2O3.

Nickel-base alloy is a type of metal material with excellent properties and is widely used in many fields. However, in the harsh environment of the acid solution, corrosion causes the reduction of the service life of the alloys, thereby limiting the alloys' use and development. In this paper, the effect of Chromium (Cr) content on the microstructure and corrosion behavior of nickel-based alloys in hydrochloric acid (HCl) was studied by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), electron backscatter diffraction (EBSD) and electrochemical workstation. Meanwhile, X-ray photoelectron spectroscopy (XPS) was used to investigate the composition and properties of the surface passive films. For the Cr20 and Cr30 alloys with a single face-centered cubic (FCC) structure, the Cr2O3 content in the passive films increased with the Cr content, effectively improving the corrosion resistance. As the Cr content continued to increase, the second phases having a body-centered cubic (BCC) lattice were precipitated both in the Cr40 and Cr50 samples, inducing microgalvanic corrosion, thus deteriorating the corrosion resistance. XPS results showed that, in the Cr30 alloy, the relative content of Cr2O3 and the bound water were the highest, indicating that its passive film had the best corrosion resistance. For the passive film, the pitting resistance was related to Cr content, appropriate Cr content improved the corrosion resistance.

This study investigates the corrosion characteristics of Co30Cr20Ni20Fe20Mo10 (Co30HEA), Co40Cr20Ni15Fe15Mo10 (Co40HEA), and Co50Cr20Ni10Fe10Mo10 (Co50HEA), designed as Co-rich high entropy alloys, compared to 316 L stainless steel and L605. Co30HEA has a single FCC phase, whereas the other two alloys exhibit a dual phase of FCC + (Cr, Mo) σ phase. The presence of high Cr and Mo content in the σ phase results in Cr depletion zones. Co30HEA shows the highest corrosion resistance in Ringer's solution, which diminishes with increasing Co content. Its passive film exhibits ideal capacitive behavior at low frequencies, indicating strong passivation. The films, primarily composed of Cr oxides and hydroxides, vary in thickness, with Co30HEA having a film about twice as thick as the others. All three alloys demonstrate pitting corrosion; however, Co30HEA shows the smallest pits mainly at grain boundaries, while the others show pits near the σ phase due to unstable passive films in the Cr and Mo-depleted zones, acting as anodic sites for galvanic corrosion.

Abstract This study investigates the corrosion behavior of laser beam-welded UNS S32304 and SS304L in 3.5% NaCl solutions, focusing on the effects of temperature. The primary objective is to enhance the understanding of corrosion resistance in welded materials and inspire advancements in corrosion mitigation strategies. The methodology involves assessing corrosion resistance under varying temperatures and comparing the performance of laser beam welding (LBW) with that of the base metals. Scanning electron microscopy analysis reveals effective passivation, while quantitative analysis indicates differences in chloride ion coverage between the weld metal and base metals. Tafel plots and electrochemical impedance spectroscopy demonstrate enhanced corrosion potential and improved barrier properties for the weld metal. Results indicate a marginal reduction in corrosion resistance at 50 °C for both base metals. LBW metals corrosion resistance demonstrates superior performance, with only 5% reduction in breakdown potential compared to 10% in base metals. Compared to the base metal, it exhibits a substantial reduction in corrosion rate, ranging from 60 to 75%. This supports enhanced corrosion resistance and material stability. Additionally, similar results are observed after the analysis with scanning electron microscopy images, reinforcing the efficacy of LBW in improving corrosion resistance of LBW UNS S32304 and SS304L. These findings underscore the potential of LBW for applications requiring robust corrosion performance. By contributing to the understanding of the corrosion behavior of laser beam-welded materials, this study addresses a critical research gap in material science and corrosion engineering. Future research may explore long-term durability and corrosion resistance under diverse environmental conditions to further elucidate the mechanisms driving the observed differences in corrosion behavior.

The effect of utilization of zinc (Zn) and graphite (Gr) as a hybrid interlayer for dissimilar lap joint of AA2024 and pure copper, employing friction stir welding (FSW), was investigated in this study. The microstructure of the samples was examined using a scanning electron microscope (SEM), and the composition of the present phases was evaluated with energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were performed to analyze the corrosion behavior. Subsequently, the post-corrosion morphology was examined using SEM and EDS. The results show that applying two passes of FSW in the presence of hybrid Zn-Gr interlayer, led to the modification of detrimental brittle intermetallic compounds (IMCs). The corrosion investigations demonstrated that the corrosion current density (icorr) in the AA2024/(Zn-Gr)/Cu sample after 1- pass FSW was reduced by about 80% in comparison to the Al/Zn/Cu sample. This behavior can be attributed to the presence of a large number of diffusion channels and the inhibitory effect of graphite particles. The 2-pass FSWed AA2024/(Zn-Gr)/Cu sample exhibited the highest level of corrosion resistance, owing to the better dispersion of graphite particles, which led to improved passivation on the aluminum side. As a result, the inherent issue of intergranular corrosion in the Al–Cu alloy was effectively resolved at the joint interface. This ultimately led to an enhanced corrosion resistance of the Al–Cu bimetals produced by FSW.

Lithium-ion batteries are superior energy storage devices that are widely utilized in various fields, from electric cars to small portable electric devices. However, their susceptibility to thermal runaway necessitates improvements in battery case materials to improve their safety. This study used electrochemical analyses, including open-circuit potential (OCP), potentiodynamic polarization, and critical pitting temperature (CPT) analyses, to investigate the corrosion resistance of super duplex stainless steel (SAF 2507) applied to battery cases in relation to post-weld heat treatment (PWHT) time. The microstructure during the manufacture, laser welding, and PWHT was analyzed using field-emission scanning electron microscopy, X-ray diffraction, and electron backscatter diffraction, and the chemical composition was analyzed using dispersive X-ray spectroscopy and electron probe micro-analysis. The PWHT increased the volume fraction of austenite from 5% to 50% over 3 min at 1200 °C; this increased the OCP from −0.21 V to +0.03 V, and increased the CPT from 56 °C to 73 °C. The PWHT effectively improved the corrosion resistance, laying the groundwork for utilizing SAF 2507 in battery case materials. But the alloy segregation and heterogeneous grain morphology after PWHT needs improvement. [ABSTRACT FROM AUTHOR]

The corrosion behavior of CoCrNi medium-entropy alloy (MEA) in the coastal marine environment polluted by excessive CO2 was investigated. Increasing NaHCO3 concentration expediates the active dissolution of the passive film and damages its protectiveness. The positive half-cycle of AC increases local acidity and encourages Cl− to adsorb on the passivation film, whereas H+ ions are easily adsorbed during the AC-negative half-cycle. H+ and Cl− as aggressive ions can significantly undermine the stability and denseness of passivation film. Furthermore, the interactive effect of alternating current and HCO3− significantly interferes with the passivation of the MEA, contributes to the nucleation of metastable pitting, and increases the occurrence probability of stable pitting, aggravating anti-corrosion performance. The cathodic reaction under the influence of alternating current is dominated by hydrogen evolution; the generated hydrogen atoms can tear the passivation film and deteriorate the corrosion resistance. [ABSTRACT FROM AUTHOR]

The corrosion behaviors of three bridge steels in a real tropical marine environment for 2 years were studied. One weathering steel (WS) was designed with higher levels of nickel, copper, and molybdenum compared to the other. These two kinds of WSs and one kind of ordinary high-strength low-alloy steel (Q345qe) were compared under two conditions (marine atmospheric zone and marine immersion zone at Sanya Marine Environmental Test Station). The morphology, corrosion rate, and corrosion product analysis of the steels were performed through SEM, XPS, FTIR and other characterization methods. The results demonstrated that weathering steels facilitate the densification of the corrosion product layer due to the addition of alloying elements Cr, Ni, and Cu, promoting rust nucleation and enhancing the compactness of the protective layer. However, in an immersion environment, the extensive erosion by chloride ions renders the benefits of WS ineffective. [ABSTRACT FROM AUTHOR]

Basalt powder (BP) is the residue of a plant that crushes basalt stones. This work deals with the effect of waste BP on the properties of cement mortars and the physical properties of hardened mortars. Modified concrete was prepared by partial replacement of BP in amount of 5, 10, 20% by weight of cement. Physico-mechanical properties and corrosion resistance were investigated. Electrochemical impedance spectroscopy (EIS) was used to examine the corrosion behavior of cement pastes with a partial addition of basalt powder in aggressive solutions of 5% NaCl and 5% MgCl2 for up to 270 days. Infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were also performed to investigate the hydration process and microstructure formation of the basalt blended paste. Results indicate that the addition of basalt powder as a partial replacement of cement influences the microstructure of the interfacial transition zone (ITZ), which is denser and stronger than in cement paste without basalt powder. The filler effect of the basalt powder improves the compressive strength of cement paste. Also, comparing BP0 and BP20 in 5% NaCl after 270 days, the partial substitution of cement with BP resulted in a higher compressive strength of 671 and 895 kg/cm2, respectively. The EIS results also showed the highest values of Rp 953 ohms cm2 after 270 days. This high corrosion resistance might indicate the binding by high Al2O3 that reduced the free aggressive chloride ions in the solution. Article Highlights: The addition of basalt powder as a partial replacement of cement, improved the compressive strength of the concrete. The physicochemical and mechanical investigations showed that the basalt addition led to physical densification and more ITZ robust of cement matrix. EIS measurements showed that BP20 sample in 5% NaCl had a high Rp, 953 ohms cm2 after 270 days indicated higher corrosion resistance. [ABSTRACT FROM AUTHOR]

The corrosion behavior of novel MgO–Mg 1.08 Al 1.84 Ti 0.08 O 4 refractories was investigated as a potential replacement for traditional MgO–MgAl 2 O 4 refractories as the inner lining of RH snorkels. The incorporation of Mg 1.08 Al 1.84 Ti 0.08 O 4 fine powder with dense microstructure resulted in superior densification and mechanical strength compared to traditional MgO–MgAl 2 O 4 refractories. The novel MgO–Mg 1.08 Al 1.84 Ti 0.08 O 4 refractories significantly enhanced their corrosion resistance, due to the reduction in porosity and pore diameter, as well as the increase in pore complexity and contact angle. These factors effectively impeded the penetration of RH slag. Additionally, the presence of Mg 1.08 Al 1.84 Ti 0.08 O 4 in contact with RH slag formed a more complex (Mg, Fe)(Al, Ti) 2 O 4 spinel solid solution, which exhibited strong Fe element absorption ability. Thus, this decreased the Fe concentration in the RH slag, resulting in an increase in liquid slag viscosity and enhancing the slag penetration resistance of MgO–Mg 1.08 Al 1.84 Ti 0.08 O 4 refractories. The microstructure of the MgO–Mg 1.08 Al 1.84 Ti 0.08 O 4 refractories featured an isolated distribution of Ca 2 SiO 4 phase, which suggested fewer channels for liquid RH slag to penetrate the refractory materials. According to Factsage 6.2 thermodynamic simulation, the dissolution of Mg 1.08 Al 1.84 Ti 0.08 O 4 into liquid slag was lower compared to the sintered MgAl 2 O 4 , which was advantageous for resisting the dissolution of refractory materials into liquid slag. [ABSTRACT FROM AUTHOR]

This study investigates the corrosion behavior of laser beam-welded UNS S32304 and SS304L in 3.5% NaCl solutions, focusing on the effects of temperature. The primary objective is to enhance the understanding of corrosion resistance in welded materials and inspire advancements in corrosion mitigation strategies. The methodology involves assessing corrosion resistance under varying temperatures and comparing the performance of laser beam welding (LBW) with that of the base metals. Scanning electron microscopy analysis reveals effective passivation, while quantitative analysis indicates differences in chloride ion coverage between the weld metal and base metals. Tafel plots and electrochemical impedance spectroscopy demonstrate enhanced corrosion potential and improved barrier properties for the weld metal. Results indicate a marginal reduction in corrosion resistance at 50 °C for both base metals. LBW metals corrosion resistance demonstrates superior performance, with only 5% reduction in breakdown potential compared to 10% in base metals. Compared to the base metal, it exhibits a substantial reduction in corrosion rate, ranging from 60 to 75%. This supports enhanced corrosion resistance and material stability. Additionally, similar results are observed after the analysis with scanning electron microscopy images, reinforcing the efficacy of LBW in improving corrosion resistance of LBW UNS S32304 and SS304L. These findings underscore the potential of LBW for applications requiring robust corrosion performance. By contributing to the understanding of the corrosion behavior of laser beam-welded materials, this study addresses a critical research gap in material science and corrosion engineering. Future research may explore long-term durability and corrosion resistance under diverse environmental conditions to further elucidate the mechanisms driving the observed differences in corrosion behavior. [ABSTRACT FROM AUTHOR]

Since F/M steel is one of the leading candidate materials for the lead-cooled fast reactor (LFR), its compatibility with the liquid LBE environment is an essential issue before application. One major way to improve LBE corrosion resistance is to control the oxygen concertation in liquid LBE for the growth of a stable, protective oxide layer on the surface of the structure material. However, the influence of the surface state on corrosion behavior is a more realistic issue when it comes to practical applications. In this study, the corrosion behavior of Si-reinforced 9Cr and 11Cr F/M steels with different surface states was investigated by a static liquid LBE corrosion test under solid-phase oxygen-controlled conditions. The result showed that at 550 °C, the coarse surface state caused dissolution behavior at the initial stage of corrosion, while the fine surface state formed the oxide layer. Moreover, at 610 °C, Si-reinforced 11Cr F/M steel shows better liquid LBE corrosion resistance due to its thinner oxide layer formation. [ABSTRACT FROM AUTHOR]

This article aims to investigate aging temperature effects on the wear and corrosion characteristics of stainless steel alloy Custom 450. Electrochemical measurements were performed in 1 M H2SO4 solution. Pin-on-disk tests and microstructural evaluations were also done. The results displayed that the steel hardness increased when the aging temperature was raised to 500 °C. However, higher temperatures resulted in a hardness reduction of about 11% compared with annealed specimens. Such observation was due to the increase in the reversed austenite content by up to 10.7%. The aged specimen's wear rate was reduced by about 85% when the aging temperature was 500 °C, based on the high hardness. The suggested wear mechanism changed from abrasive and cutting wear mode to the adhesive wear mechanism when the aging temperature increased. Tafel polarization tests showed that corrosion rates of specimens decreased by about 99% when the aging temperature increased to 600 °C. This was attributed to increasing the amount of the reversed austenite phase, and Ni-rich precipitates in the aged martensite matrix. [ABSTRACT FROM AUTHOR]

The non-equiatomic Al0.32CrFeTi0.73(Ni1.50−xMox) (x = 0, 0.23) high-entropy alloy (HEA) coatings were prepared by the high-velocity oxygen fuel (HVOF) method. The microstructures and corrosion behaviors of the HVOF-prepared coatings were investigated. The corrosion behaviors were characterized by polarization, EIS and Mott-Schottky tests under a 3.5 wt.% sodium chloride aqueous solution open to air at room temperature. The Al0.32CrFeTi0.73Ni1.50 coating is a simple BCC single-phase solid solution structure compared with the corresponding poly-phase composite bulk. The structure of the Al0.32CrFeTi0.73Ni1.27Mo0.23 coating, combined with the introduction of the Mo element, means that the (Cr,Mo)-rich sigma phase precipitates out of the BCC solid solution matrix phase, thus forming Cr-depleted regions around the sigma phases. The solid solution of large atomic-size Mo element causes the lattice expansion of the BCC solid solution matrix phase. Micro-hole and micro-crack defects are formed on the surface of both coatings. The growth of both coatings' passivation films is spontaneous. Both passivation films are stable and Cr2O3-rich, P-type, single-layer structures. The Al0.32CrFeTi0.73Ni1.50 coating has better corrosion resistance and much less pitting susceptibility than the corresponding bulk. The corrosion type of the Mo-free coating is mainly pitting, occurring in the coating's surface defects. The Al0.32CrFeTi0.73Ni1.27Mo0.23 coating with the introduction of Mo element increases pitting susceptibility and deteriorates corrosion resistance compared with the Mo-free Al0.32CrFeTi0.73Ni1.50 coating. The corrosion type of the Mo-bearing coating is mainly pitting, occurring in the coating's surface defects and Cr-depleted regions. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) was performed on an AZ91 magnesium alloy cladding layer fabricated by a cold metal transfer (CMT) technique. Electrochemical properties and immersion corrosion behavior of the cladding layer before and after FSP in 3.5 wt.% NaCl solution were investigated. After applying the FSP, the corrosion potential and corrosion current density of the cladding layer increased from −1.455 V to −1.397 V and decreased from 4.135 μA/cm2 to 1.275 μA/cm2, respectively. The results of OM and SEM displayed the refinement of grains and the dispersion of β-Mg17Al12 second phase in the friction stir processed (FSPed) cladding layer and more severe corrosion of the unprocessed sample. The corrosion rate of the FSPed cladding layer was lower, and a more compact corrosion product film was formed on the surface of the FSPed cladding layer. EDS results and XRD patterns showed that the corrosion products was mainly composed of Mg(OH)2. The increase in Al content in the α-Mg matrix, grain refinement, and fragmentation and dispersion of the β-Mg17Al12 second phase induced by FSP were the main factors that led to the improvement in corrosion resistance of the cladding layer of the AZ91 magnesium alloy fabricated by CMT. [ABSTRACT FROM AUTHOR]

In order to overcome the serious corrosion problem of furnace hearth refractory materials for smelting reduction ironmaking, the Cr 2 O 3 –Al 2 O 3 –MgO–ZrO 2 refractories were synthesized, and the phase component, microstructure, mechanical characteristics, and slag erosion behavior of composite refractories were investigated and evaluated. The results indicate that the composite refractories mainly consist of Mg(Al, Cr) 2 O 4 spinel phase, (Al, Cr) 2 O 3 solid solution and ZrO 2. The content of Mg (Al, Cr) 2 O 4 spinel significantly increases with the increasing MgO content, while the content of (Al, Cr) 2 O 3 obviously decreases. Furthermore, the comprehensive mechanical properties of the MgO modified composite refractories can be obviously enhanced by increasing the MgO content, and sample S4 presents the best mechanical characteristics when the MgO addition is 10 wt%. The corresponding hardness, compressive strength and bending strength are 14.22 GPa, 267.14 MPa and 80.0 MPa, respectively. This is mainly because the formation of Mg(Al, Cr) 2 O 4 significantly improves the densification of composite refractories, and a large number of high-strength Mg (Al, Cr) 2 O 4 spinel "bridge" formed between the large-sized (Al, Cr) 2 O 3 grains. The erosion test results indicate that increasing the MgO content can significantly improve the slag infiltration resistance of composite refractories, because the formation of Mg (Al, Cr) 2 O 4 spinel layer significantly improves the densification of MgO reinforced composite refractories. Although the slag corrosion resistance of Mg(Al, Cr) 2 O 4 is lower than that of (Al, Cr) 2 O 3 , the Cr 2 O 3 –Al 2 O 3 –MgO–ZrO 2 refractories still presents good erosion resistance, permeability resistance, and excellent mechanical characteristics. [ABSTRACT FROM AUTHOR]

Nacre-inspired metal matrix composites have received much attention due to their excellent deformation coordination ability, which can achieve the synergy of strength and ductility. The preparation of nacre-like Al matrix composites by freeze casting has been a promising application, but the continuous ceramic-rich layer affects the corrosion resistance of the composites, facing complex corrosion problems during service. In this work, the microstructure and corrosion behavior of the nacre-inspired (TiBw-TiB2)/Al composites fabricated by freeze casting and squeeze casting were systematically studied. The results indicated that the Al layers and ceramic-rich layers had little change, about 35 μm and 31 μm, respectively, with an increasing ratio of the Ti/TiB2. Meanwhile, a high Ti/TiB2 ratio resulted in an increase in the Fe-Ti intermetallic phases, which was detrimental to the corrosion performance of the composites and was prone to pitting. The electrochemical test results showed that the 3Ti7TiB2 composite had the lowest corrosion current density (15.9 μA) and intergranular corrosion depth (231 μm), indicating that it had the best corrosion resistance, which can be attributable to its stable and dense passivation film. Two different corrosion phenomena during the intergranular corrosion test existed in the present nacre-inspired (TiBw-TiB2)/Al composites: intergranular corrosion in the Al matrix layer and pitting corrosion in the ceramic-rich layer. Among all the composites, the corrosion depth of the 3Ti7TiB2 composite was the smallest and significantly less than that of the 2024Al alloy. In addition, the continuous ceramic-rich layer acted as a corrosion channel during corrosion, significantly degrading the corrosion resistance of the nacre-like Al composites. [ABSTRACT FROM AUTHOR]

SiCf/SiC composites, as promising materials for the hot‐section components of turbine engines, are susceptible to hot corrosion due to the steam environments. Especially, under rotational and thermal stress, numerous microcracks may be generated in the SiCf/SiC ceramic matrix, which can trigger the rapid invasion of corrosive gases and deteriorate the composite mechanical properties. Therefore, it is of great importance to investigate the degradation mechanisms of SiCf/SiC with precracks existing. Here, the corrosion behavior of precracked SiCf/SiC in the Na2SO4‐wet‐oxygen environment was evaluated. By comparing mechanical evolution under different corrosion conditions, microfailure mechanisms of SiCf/SiC were revealed. The results indicate that brittle cracking of the matrix and oxidation erosion of fibers are the key factors in reducing the tensile strain of composites. Specifically, the composite damage resistance increases at 67 MPa‐1300°C. At this point, the prestress level is moderate and close to the matrix cracking limit. The prefabricated microcracks can be healed at 1300°C by liquid oxidation products, which hinders cracks bridging large‐scale. This study is conducive to a better understanding of failure mechanisms of SiCf/SiC in complex service environments. [ABSTRACT FROM AUTHOR]

The present study presented the systematic investigations on the influence of Co and Cu on the corrosion behaviors and wear resistance of Ti–Nb based shape memory alloys. The results demonstrated that the addition of Co and Cu can effectively enhance the corrosion resistance of Ti–Nb based shape memory alloys. By optimizing the chemical composition, the superior corrosion resistance with (φcorr = –0.95499 V, Jcorr = 357.92 μA cm−2) and (φcorr = –0.96775 V, Jcorr = 467.54 μA cm−2) can be obtained in Ti–Nb–Co1.0 and Ti–Nb–Cu1.5 shape memory alloys, respectively. Similarly, the wear properties of Ti–Nb based shape memory alloys were also dependent on the ternary alloying elements. The friction coefficient of Ti–Nb based shape memory alloy firstly decreased and then increased with the content of ternary alloying element increasing. And then decreased again, as the exceeding ternary alloying element was added. In addition, the wear behaviors of Ti–Nb based shape memory alloys can be attributed to the combination of abrasive wear, adhesive wear, and oxidative wear, irrespective of the types of ternary alloying elements. In contrast, Ti–Nb–Cu5.0 shape memory alloy has the lowest friction coefficient of 0.45, which is smaller than that (0.50) of Ti–Nb–Co5.0 shape memory alloy. [ABSTRACT FROM AUTHOR]

In this work, the effect of laser shock peening (LSP) on the electrochemical behavior of HSLA steel (ASTM A 588 Grade D) in 3.5 wt.% NaCl solution was investigated. The microstructural evolution, micro-texture development, surface roughness, residual stress development, microhardness, dislocation density, potentiodynamic polarization, and electrochemical impedance spectroscopy were studied in depth. The corroded surfaces (with and without LSP) were characterized using scanning electron microscopy and Raman spectroscopy for understanding the nature of the passive film formation and its stability. The results revealed that LSP treatment marginally refines the near-surface microstructure from 9.1 to 7.4 μm and generated high compressive residual stress (CRS) of about 500 MPa on the top surface; such variation happened due to severe plastic deformation during LSP. The micro-texture analyses of the laser-peened specimens (on the surface) revealed that {011} <111> texture components were significantly increased while the γ-fiber weakened after laser-peening. Dislocation density was obtained ~ 9.266 × 1012 on the unpeened and ~ 1.158 × 1013 on the laser-peened surfaces, indicating that higher pressure shock waves plastically deformed the top layer of the peened specimen. The corrosion studies indicated about 4 times improvement in the corrosion resistance of the peened specimens—the combined effects of LSP-induced gradient CRS and refined microstructure improved the corrosion resistance. The EDS and Raman spectroscopy results demonstrated the persistence of a compact and continuous passive oxide film/layer, primarily made of Fe2O3, on the surface of the laser-peened specimens. [ABSTRACT FROM AUTHOR]

Brazing is a joining process that involves melting a filler metal and flowing it into the joint between two closely fitting parts. While brazing is primarily used for joining metals, it can also be adapted for certain coating deposition applications. The present study investigates the microstructure and corrosion behavior and sliding wear resistance of WC (Tungsten Carbide)-CoCr-Ni reinforced Co-based composite coatings deposited onto the surface of AISI 904L stainless steel using a vacuum brazing method. The primary objective of this experimental work was to evaluate the influence of WC-based particles added to the microstructure and the properties of the brazed Co composite coating. The focus was on enhancing the sliding wear resistance of the coatings while ensuring that their corrosion resistance in chloride media was not adversely affected. The morphology and microstructure of the composite coatings were investigated using scanning electron microscopy (SEM) and phase identification by X-ray diffraction (XRD). The SEM analysis revealed in the coating the presence of intermetallic compounds and carbides, which increase the hardness of the material. The sliding wear resistance was assessed using the pin-on-disk method, and the corrosion properties were determined using electrochemical measurements. The results obtained showed that as the WC particle ratio in the Co-based composite coating increased, the mechanical properties improved, the alloy became harder, and the tribological properties were improved. The evaluation of the electrochemical tests revealed no significant alterations of the manufactured composite in comparison with the Co-based alloys. In all cases, the corrosion behavior was better compared with that of the stainless-steel substrate. [ABSTRACT FROM AUTHOR]

In this study, the welding performance of three filler wires, ER4043, ER5356, and the newly developed FMg0.6, were systematically investigated in the gas metal arc welding of high-strength AA6011-T6 plates. An extensive analysis of the microstructural evolution, mechanical properties, fatigue resistance, and corrosion behavior of different weldments was conducted. The ER4043 and FMg0.6 joints exhibited finer grain sizes in the fusion zone (FZ) than the ER5356 joint. The as-welded ER5356 and FMg0.6 joints exhibited higher hardness and tensile strength values than the ER4043 joint. The FMg0.6 joint demonstrated the highest mechanical strength among all of the joints with superior fatigue resistance under both the as-welded and post-weld heat treatment (PWHT) conditions. In the as-welded state, the ER5356 joint exhibited the lowest corrosion resistance, attributed to the precipitation of β-Al2Mg3 at the grain boundaries. The FMg0.6 joint, characterized by a high-volume fraction of eutectic Mg2Si in the as-welded state, exhibited a higher corrosion rate than that of the ER4043 joint. However, the PWHT effectively improved the corrosion resistance of the FMg0.6 joint. Given its excellent tensile properties, superior fatigue properties, and satisfactory corrosion resistance, particularly with PWHT, the newly developed FMg0.6 filler has emerged as a promising candidate for welding high-strength 6xxx alloys. [ABSTRACT FROM AUTHOR]

In this work, a novel type of nuclear shielding material capable of shielding γ rays and neutrons, W-B-Ni-Fe cermets, was synthesized using W, NiB, and Fe powders by reactive boride sintering. The cermets possessed a constant (Ni + Fe)/B atomic ratio of 1.50 and various W/B atomic ratio (ARWB) of 8.26, 3.25, 1.88 and 1.24, respectively. Microstructure and mechanical properties were characterized and analyzed, and corrosion behavior was discussed using electrochemical method in 1.0 M H2SO4 aqueous solution. After sintering, the cermets were composed of orthorhombic W2(Ni,Fe)B2 hard phase, W phase and Ni based binder phase. The homogeneous microstructure with both fine W2(Ni,Fe)B2 and W particles was obtained when ARWB was 3.25. At room temperature (RT), the hardness increased monotonically with ARWB decreasing, while the compressive and bending strengths peaked when ARWB was 3.25 due to the cooperative effect of hard-phase and grain-refinement strengthening. At high temperature (500 ℃), the presence of ductile W phase enabled an increase of bending strength compared to that at RT. The corrosion of cermets in 1.0 M H2SO4 solution began with active dissolution of Ni based binder phase, and then the passivation process occurred with the formation of blue WO3-x phase. With ARWB decreasing, Icorr was first sharply decreased and then sharply increased. The impedance value of cermet was lowest when ARWB was 3.25 which is due to the relatively lower forming ability of passive film.