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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.

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.

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.

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.

To address the current issues of brittleness and lower mechanical performance for Zn alloys, the Zn–Mn–Li system that has significant potential for enhancing strength and toughness is selected for the design, fabrication, and investigation. Li and Mn are selected as alloying elements, and a series of Zn-0.4Mn-xLi alloys are prepared. A comprehensive study of as-cast alloys is conducted on the microstructure, mechanical properties, and corrosion behavior. The results reveal that the initially precipitated β-LiZn4 phase in the as-cast Zn-0.4Mn-xLi alloys gradually transforms into a β-LiZn4/Zn lamellar structure with the increase of Li content. The β-LiZn4/Zn lamellar structure significantly contributes to the strength of the alloy. The as-cast Zn-0.4Mn-0.8Li alloy exhibits optimal mechanical strength, with yield strength and ultimate tensile strength of 203.2 ± 8.9 MPa and 271.5 ± 20.0 MPa, respectively. Electrochemical and immersion experiments indicate a dense Li-rich corrosion product layer formed on the alloy surface suppresses the generation of pitting corrosion and enhances the corrosion resistance of the alloy. These results manifest that the Li content of the Zn–Mn–Li alloy has a significant influence on the performance, such as the microstructure, mechanical properties, and corrosion behavior. According to the results of mechanical properties and corrosion behavior, Zn-0.4Mn-0.8Li alloy exhibits an optimal comprehensive performance, which provides valuable insight for the development of superior Zn–Mn–Li alloys.

Balancing mechanical and corrosion performance is a decisive factor in the use of high entropy and medium entropy alloys (H & MEAs) as advanced engineering structural materials. This study investigates the microstructure of Fe77.3-xMnxSi9.1Cr9.8C3.8 (x = 14, 23.2) HEAs by combining experiments and first-principles calculations to elucidate the effects of adjusting Mn content on the mechanical and corrosion properties of FCC and FCC + HCP phases. The results demonstrate that HEAs with low Mn content exhibit a single FCC phase, whereas increasing Mn content not only precipitates the HCP phase but also refines the grain size. The yield strength, compressive fracture strength, work hardening index, and plasticity of Fe77.3-xMnxSi9.1Cr9.8C3.8 (x = 14, 23.2 at.%) HEAs are 1300 and 1526 MPa, 2380 and 2332 MPa, 0.42 and 0.36, 16.7% and 16%, respectively. Both HEAs exhibit superior electrochemical and salt spray corrosion performance compared to 304 stainless steels, with the Fe63.3Mn14Si9.1Cr9.8C3.8 alloy performing the best, exhibiting a self-corrosion potential of −0.523V and a self-corrosion current density of 2.605 × 10−6 A cm−2. The excellent corrosion resistance of Fe63.3Mn14Si9.1Cr9.8C3.8 can be attributed to the moderate grain size, resulting in excellent passivation film characteristics, and the lower Mn content, leading to a higher Cr2O3 content in the passivation film. First-principles calculations reveal that Fe63.3Mn14Si9.1Cr9.8C3.8 has a lower density of states number at the Fermi level (i.e., Fe63.3Mn14Si9.1Cr9.8C3.8 is 214.145eV, Fe54.1Mn23.2Si9.1Cr9.8C3.8 is 337.077eV), a wider pseudogap width, higher work function (5.700ev, 5.189ev), and better stability. Additionally, there exists a strong trade-off between corrosion and mechanical properties due to the influence of the HCP phase and grain size.

Steel containers used for geological disposal of high-level radioactive waste will be gradually thinned or even perforated due to corrosion, which will lead to radiolysis of nuclides when they contact with infiltrated groundwater and produce H2O2. This work focused on investigating the influence of H2O2 concentration (0%, 0.001%, 0.01%, 0.1% and 1% by volume) on the corrosion behavior of NiCu low alloy steel as the candidate material for containers was comparatively studied by combining corrosion weight loss test, corrosion product analysis, morphology characterization, thermodynamic analysis and electrochemical measurements. As [H2O2] = 0.001%, H2O2 inhibited the formation of γ-FeOOH and enhanced the compactness of rust layer, which effectively blocked the migration of aggressive ions and slowed down the cathodic reduction reaction of rust, thus improving the corrosion resistance of NiCu steel. With the increase of [H2O2] (0.01%→1%), the cathodic process of NiCu steel corrosion was promoted by the increase of dissolved oxygen involved in cathodic depolarization. Meanwhile, the relative content of Fe3O4 in the rust increased, while Fe6(OH)12SO4 and Fe6(OH)12CO3 decreased obviously, which led to the loose and porous rust layer, thus accelerating the corrosion of NiCu steel.

Having homogenized the as-cast AlCoCrFeNi2.1 high-entropy alloy followed by cold rolling and subsequent annealing, this study produces surface nanocomposite using friction stir processing (FSP). Three weight percentages of SiC nanoparticles sized between 45 and 60 nm were added during FSP. The microstructural evolutions and corrosion behavior were assessed after and before FSP. As part of the investigation, a series of potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) were conducted in a 3.5 wt% NaCl solution. Through friction stir processing, the initial microstructure underwent significant modification due to dynamic recrystallization and the Zener pinning applied by SiC-reinforcing nanoparticles. The hard B2 phases, which function as preferred sites for localized corrosion, were broken and redistributed during FSP, resulting in a notable increase in corrosion resistance. After performing FSP, the cold-rolled and annealed sample exhibited a significant increase in corrosion resistance, from 1.7 kΩ.cm2 to 129.4 kΩ.cm2.

Biodegradable pure Zn and zinc alloys have received much attention in recent years, but the mechanical properties, corrosion behavior and biocompatibility of the previous reported pure zinc and zinc alloys do not fully meet the clinical requirements. Alloying and deformation technology are widely used in improving the properties of biodegradable pure Zn and zinc alloys. In this work, we have developed two new types of binary zinc alloys with the two rare earth elements (REE) cerium (Ce) and ytterbium (Yb). The effects of Ce and Yb on the microstructure, mechanical properties, corrosion behavior, in vitro biocompatibility of biodegradable Zn-xCe and Zn-xYb (x = 0.1, 0.2, 0.5, 1.0 wt %) were systematically investigated. The ultimate tensile strength, yield strength and elongation of Zn-xCe and Zn-xYb alloys are significantly improved compared with pure Zn. The Zn-xCe and Zn-xYb alloys have superior antibacterial properties The osteoblast MC3T3-E1 cells exhibited excellent cell activity with polygonal or fusiform extension and adhesion cultured in the series of Zn-xCe and Zn-xYb alloys’ extract solutions, indicating the good in vitro biocompatibility of Zn-xCe and Zn-xYb alloys. This work demonstrated that the Zn-xCe and Zn-xYb binary alloys have great potential as new biodegradable metals for future biomedical implants and devices.

The study investigated the microstructures and corrosion behaviors of Hastelloy X (HX) and HX reinforced by cerium oxide particles (HX-C) produced by selective laser melting (SLM) and compared to the wrought equivalent (HX-W). The aim was to eliminate hot cracking and investigate the HX's corrosion behavior in the presence of cerium oxide particles. The HX samples showed fine cellular and columnar solidification structures with uniform-size sub-cells and severe microcracking. Incorporating cerium oxide particles (1 wt%) resulted in finer and relatively equiaxed grains without microcracking. The HX-W alloy contained a micron-sized carbide (Mo-rich M6C type) within the matrix. The HX-C sample displayed higher porosities compared to the HX sample (1.8 % against 0.3 %). Potentiodynamic polarization and electrochemical impedance spectroscopy tests were conducted in a standard NaCl solution at temperatures of 25, 50, and 70 °C to assess the corrosion behavior of Hastelloy samples. The HX-C matrix showed superior corrosion resistance compared to the HX-W and HX samples due to its finer grain structure and stable passive layer formation. Cerium oxide particles were found to be efficient in decreasing hot cracking and improving corrosion resistance.

A novel Zr–Ti conversion coating (ZrTiCC) was fabricated on 6016 aluminum alloy. The coating thickness was evaluated, and the corrosion resistance of the coating was investigated through CuSO4 drop experiments to determine the optimum process. Potentiodynamic polarization results revealed the corrosion current density of ZrTiCC (4.821 μA/cm2) was lower than that of bare specimen (12.263 μA/cm2), and the δE of ZrTiCC (0.752V) was significantly lower than bare specimen (0.087 V). Scanning electron microscope and energy dispersive spectrometer was used to characterize the morphology and composition changes of the coating during its growth. The coating was proved to have a double-layer structure, and cracks appeared when the coating thickness continued to increase, which reduced the corrosion resistance. The growth mechanism of the coating was explained in detail. X-ray photoelectron spectroscopy was used to determine the components of the coating, which comprised Al2O3 at the base, with TiO2, AlF3, and ZrF4 at the top and ZrO2 evenly distributed throughout. Bode diagram revealed the impedance modulus of the coating at low frequency was increased to 8.6 × 104 Ω/cm2 after five days immersion in 0.5 M NaCl. The coating's self-sealing behavior and active protection may relate to the formation of SiO2, as well as the dissolution and regeneration of the upper coating (AlF3 and ZrF4) on 6016 aluminum alloy.

The effect of Ce on the corrosion behavior of Fe–36Ni Invar alloy was investigated in a 3.5 wt% NaCl solution. The proper addition of Ce enhanced the corrosion resistance. The second-phase particles were gradually transformed in type, size, and number following the addition of Ce, which alleviated the localized corrosion behavior. The appropriate Ce content increased the fraction of low coincident site lattice boundaries. Furthermore, the enhancement of protectiveness and compactness of the passive film was achieved. However, overadded Ce led to the degradation of corrosion resistance. 0.0170 wt% Ce was advised for the sake of the enhancement of corrosion resistance.

Degradable zinc (Zn) based metals exhibit great promise as potential load-bearing bone-implant materials due to their suitable biodegradability, good fabricate-friendliness, biocompatibility, and favorable osteogenesis-promoting capacity. Nevertheless, most as-cast Zn-based metals display poor mechanical properties due to their coarse grain size and few slip systems, which is challenging to meet bone-implant application requirements. Herein, the alloying using rare earth (RE) elements of neodymium (Nd), yttrium (Y), and holmium (Ho) combined with hot-rolling was used to prepare the hot-rolled (HR) Zn-5RE binary alloys for load-bearing bone fixation or bone repair applications. HR Zn–5Y sample demonstrated the best mechanical properties matching with an ultimate tensile strength of ∼260 MPa, yield strength of ∼200 MPa, elongation of ∼43.5%, strength-elongation product of ∼11.3 GPa%, and macro-hardness of ∼104.7 HB among the HR samples, close to the requirements of mechanical properties for degradable bone-implant materials. HR Zn–5Y sample exhibited the lowest corrosion rate of ∼178 μm/y measured by electrochemical polarization testing, the degradation rate of ∼29 μm/y measured by static immersion testing, and high tribological properties in Hanks’ solution. The diluted Zn–5Y extract showed an appropriate cytocompatibility to 3T3 and MG-63 cells and moderate osteogenic differentiation ability to 3T3 cells among HR Zn-5RE and pure Zn extracts. Meanwhile, the HR Zn–5Y sample showed a suitable and effective antibacterial capacity against S. aureus and E. coli. Overall, the HR Zn–5Y sample is a promising moderate load-bearing bone-implant material for bone pins, plates, and guiding bone regeneration membrane application.

The corrosion behavior and chloride threshold concentration of AISI 316L stainless steel reinforcement bar (rebar), subjected to high-energy shot peening (HESPed), are compared with its solution-annealed (SAed) counterpart in simulated concrete pore solution (CPS). X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that HESP significantly reduces the surface grain size to the ultrafine/nanometric range and increases the density of various dislocation structures, including dislocation walls and cells. This augmented presence of grain boundaries and dislocations, acting as high diffusivity paths, contributed to the formation of a thicker surface film with higher Cr content and lower donor/acceptor density in the HESPed sample compared to the SAed. Moreover, corrosion behavior analyses in CPSs with NaCl concentrations ranging from 0.0 to 2.0 M demonstrated that HESPed samples exhibit broader passivation ranges, more positive corrosion potentials, and higher polarization resistance under equivalent chloride concentrations. Additionally, threshold chloride concentrations obtained from the potentiodynamic polarization tests show values between 0.5 and 1.0 M for the SAed and between 1.0 and 1.5 M for the HESPed samples. Based on diffusion equations, a physical model is proposed to elucidate the improved behavior resulting from the HESP treatment.

The cooling curves of the Al–Zn–In–Mg–Ag alloys in copper mold, iron mold, and 400 °C-preheated iron mold cast were simulated and three solidification rates were calculated to be 7.05 °C/s, 0.76 °C/s, and 0.28 °C/s. The effects of cooling rate on the microstructure, electrochemical characteristics, and corrosion morphologies of Al–Zn–In–Mg–Ag alloys are investigated. The results demonstrate that the alloy with a low cooling rate has the lowest self-corrosion rate (0.09 mm/year), the highest actual capacity (2503.16 Ah/Kg2), as well as the highest anode current efficiency (87.46%). The anode current efficiency of the Al alloys is affected by the self-corrosion and the detachment of the second phases and grains. As the cooling rate decreases, the grain size becomes larger, the amount of the MgZn2 second phase decreases, and the content of In, Zn, and Ag activation elements increases in the matrix. The corrosion of the Al–Zn–In–Mg–Ag alloy initiates from the micro-galvanic corrosion between the MgZn2 second phase and the Al matrix. It then extends along the grain boundaries and towards the intragranular, accompanied by the shedding of the MgZn2 particles and the grains.

Pure Zn is well-known for its appropriate corrosion rate, making it suitable for use as future absorbable implants. Yet, it suffers from insufficient strength, thus, both plastic deformation and alloying are required. Hydrostatic extrusion has proven to be an efficient technique, providing high mechanical properties for zinc alloys. However, its effect on degradation rate and biocompatibility of Zn alloys remains unknown. Thus, within the present study, an attempt to evaluate those properties has been made on hydrostatically extruded pure Zn, Zn–Mg and Zn–Mg–Cu alloys. The materials were characterized by advanced microscopy techniques and uniaxial tensile tests. Corrosion properties were assessed based on electrochemical and static immersion tests. Finally, the cytotoxic effect of zinc extracts on endothelial cells were examined by standard MTT assays combined with confocal imaging.The results showed that hydrostatic extrusion results in significant refinement of α-Zn grains and the intermetallic phase Mg2Zn11 for the investigated alloys. The alloys exhibited ultimate tensile strength exceeding 300 MPa and elongation higher than 20%. Corrosion tests demonstrated that all the materials showed a similar level of degradation rate. Moreover, the uniform distribution of the intermetallic phase contributed to homogeneous corrosion of Zn alloys. Biological studies indicated that the least cytotoxic response in endothelial cells was obtained for the Zn–Mg alloy. Such an effect was caused by the limited amount of released Zn ions in the favor of Mg ions.The refinement of α-Zn grains and intermetallic phases caused by hydrostatic extrusion were key factors determining the performance of Zn-based materials.

In this study, we have developed a class of new Co–Cr–Mo–Nb–B high-entropy metallic glass alloys with high stability and high corrosion resistance. It was found that for Co26Cr26Mo26Nb7B15 metallic glass, the glass transition temperature reached to 1058 K, and the initial crystallization temperature of Co24.5Cr26.5Mo26.5Nb7.5B15 metallic glass was as high as 1132 K. There is a large hardness of 18.1 GPa and Young's modulus of 267 GPa of Co27.5Cr27.5Mo26.5Nb3.5B15 metallic glass. The excellent thermodynamic property and mechanical properties were proved to be related to the covalence bond and hybridization of metal-metalloid bonds. The Co–Cr–Mo–Nb–B metallic glasses exhibited a lower self-corrosion current density and higher self-corrosion voltage compared with 316 in 1 M hydrochloric acid solution, and the high corrosion resistance could be attributed to passive films enriched with Cr3+ and Mo4+. These findings provide a new and effective way to design high-entropy metallic glasses with excellent comprehensive properties and suitable for high stability applications.

To replace the hard chrome plating process, chromium-rich stainless steel coatings with the thickness of over 500 μm are deposited on 27SiMn substrates by the high efficiency (0.5 m2/h) processes of ultra-high speed laser cladding (UHS) and broad beam laser cladding (BLC). The solidification process and microstructure characteristics, affected by the UHS's high cooling rate and BLC's broad energy input, are analyzed respectively using optical microscope, SEM and TEM, followed by the investigation of corrosion behavior via the kinetic potential test in 3.5% NaCl solution. The intrinsic relationship between microstructure and corrosion behavior is discussed from the viewpoint of solidification and corrosion mechanisms.

Ga and Ag elements with good biocompatibility are introduced into a Mg–2Zn alloy to design an antibacterial alloy able to inhibit the bacterial infection of bone implants. The effects of Ga/Ag element on the corrosion behavior, cytotoxicity, and antibacterial activity of the as-extruded Mg–2Zn alloy are investigated in vitro. The immersion measurement results show that the mass loss rate of the Mg–2Zn alloy increases from 0.09 ± 0.006 mm/y to 0.24 ± 0.03 mm/y after the addition of 0.5 wt% Ga and 0.5 wt% Ag. This is due to that Ga and Ag elements can increase the cathodic current density and reduce the charge transfer resistance (Rct). Furthermore, Ag is enriched in the Mg7(ZnAg)3 phase, resulting in an increase in the micro-galvanic corrosion and the maximum local corrosion depth. The cytotoxicity tests reveal that Ag and Ga do not induce toxicity to osteoblastic cells (MC3T3-E1) after incubation for 72 h. Moreover, the addition of Ag and Ga increases prominently the antibacterial activity of Mg–2Zn alloys, which is principally associated with the release of Ga and Ag ions and the alkaline antibacterial environment.

The study utilizes a multi-directional compression (MDC) process on a basal-textured ZK60 alloy with the aim of inducing extensive twinning, which is followed by an aging treatment on the pre-deformed sample. The mechanical response and corrosion behavior of the deformed and aged samples are systematically investigated. The MDC process effectively generates numerous {10 1‾ 2} twins with increased compression passes, resulting in the enhanced grain refinement. The interplay between twins and numerous dislocations formed during pre-deformation plays a crucial role in altering both the distribution and morphology of the second phase precipitated during aging. During the aging process, the alloy exhibits a higher concentration of dense rod-like β′ phase and disk-like β″ phase. Remarkably, the compressive yield strength and ultimate strength of aged ZK60 alloy along the rolling direction are significantly improved without obvious compromise of ductility by pre-compression. Notably, the yield strength of the sample after 12-passes compression and aging (APD-12) is approximately 45 % higher than that of the sample without pre-compression (APD-0). Furthermore, the corrosion resistance of ZK60 alloy displays notable improvement upon pre-compression treatment. Specifically, the hydrogen evolution in the APD-12 sample is halved compared to the APD-0 sample. Electrochemical assessments were conducted on both pre-compressed and non-pre-compressed samples, revealing their distinct behaviors. Furthermore, an in-depth exploration has also been undertaken into the underlying mechanisms contributing to the enhancement of mechanical properties and corrosion resistance resulting from the pre-compression.

The corrosion behavior and corrosion mechanism of the Pb-rich phase and Cu-rich structure of the Sn–Pb bronze alloy in a high-chloride and high-humidity environment were studied. The phase composition of the bronze alloy was analyzed by observing the metallographic and EPMA element distribution, the potential of the microstructure was characterized by SKPFM. The corrosion products and morphology results after electrochemical and neutral salt spray tests were analyzed. The results showed that the matrix structure of bronze material was composed of Pb-rich phase and Cu-rich structure (α(I) phase and (δ+α(II)) eutectoid). During the corrosion process, the rich Pb phase preferentially corroded as the anode and diffused towards the surroundings, while the rich Cu structure served as the cathode. In the rich-Cu structure, compared with δ, the α phase was used as the anode. The corrosion products on the alloy surface mainly included Cu2O, PbCO3, and Cu2(OH)3Cl. As the corrosion gradually deepened along the depth of α phase, the galvanic couple effect between α phase and δ phase and the “oxygen concentration cell” effect gradually increased.

This study delves into the intricate corrosion behavior of ferrous and non-ferrous alloys in the challenging Antarctic marine atmosphere. Despite the harsh conditions and exceptionally low anthropogenic emissions in Antarctica, materials are still susceptible to severe corrosion. The investigation focuses on two materials: Q235 carbon steel and T2 copper. Both display distinct corrosion cases between their skyward and groundward sides due to the abrasive impact of persistent strong winds carrying ice particles and grit. Electrochemical reactions at the anode and cathode drive surface corrosion processes, involving Cl− and SO42−, ultimately leading to the formation of various corrosion products. The study highlights the role of sulfur-containing aerosols, Methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO42-) in corrosion processes, as well as the interaction between Cl− and copper in forming corrosion products. The findings emphasize the complex interplay of environmental factors like wind, ice cover, and aerosols with materials, leading to diverse corrosion products and surface transformations. Further research is crucial to gain a comprehensive understanding of corrosion challenges in extreme environments like Antarctica and to develop effective mitigation strategies.

Five Cr-containing refractory high-entropy alloy (RHEA) coatings were prepared by magnetron sputtering technology and then exposed to static lead–bismuth eutectic to investigate their oxidation resistances at 550–650 °C. The obtained TiNbCrMoV coating had a BCC crystalline structure, while the others were amorphous. The TiNbCrMoV coating exhibited the best corrosion resistance, followed by TiNbZrCrV and CrNbZrMoV coatings, and finally TiCrZrMoV and TiNbZrMoCr coatings. The excellent corrosion resistance of TiNbCrMoV coating was mainly attributed to the presence of grain boundaries which provided the diffusion channels of atoms, thus forming a protective oxide layer. Possible mechanisms were proposed to help understand the corrosion behaviors of these RHEA coatings.

Sulfate-reducing Bacteria (SRB) corrosion is a serious threat to the safety of marine pipelines.To reveal the influence of the corrosion behavior of X60 pipeline steel in the presence of SRB cultured in seawater and mud from the East China Sea The corrosion behavior of X60 pipeline steel was studied with weight loss measurements, microstructure and membrane composition analysis, electrochemical measurements The corrosion rate in sterile seawater is 0.11 mm/y, whereas, in SRB-infested seawater, it increases by 245 % to 0.38 mm/y. In sterile sea mud, the corrosion rate is 0.15 mm/y, but in SRB-infested sea mud, it increases by 87 % to 0.28 mm/y. In the corrosive environment of seawater and mud in the East China Sea, SRB significantly accelerates the microbial corrosion of X60 pipeline steel. These findings provide theoretical guidance for further research on SRB corrosion mechanisms and corrosion control of marine pipelines.

In this study, the effects of adding sub-micron hydroxyapatite (HA) particles were investigated on high cycle fatigue (HCF) and corrosion behaviors of Mg3Zn magnesium alloy. To this end, the Mg3Zn alloy and Mg3Zn/2.5 wt%HA bio composite were fabricated using mechanical-electromagnetic stir casting method followed by hot extrusion process. The results of the microstructural evaluation showed that grain refinement occurred in the composite by 48 % and Vickers microhardness increased approximately by 12 %. According to the results of the pH and weight loss measurements during the immersion tests, the presence of sub-micron HA particles increased the pH of the simulated body fluid (SBF) containing the composite specimens because of the micro-galvanic corrosion between the primary phase and the secondary phase of Ca2Mg6Zn3 in the matrix. However, a thicker protective surface layer formed on the composites, which may lead to a more desirable protection in the longer immersion time, compared to those of the monolithic alloy. Under the tensile monotonic load, the composite exhibited a moderate increase in the yield stress and a reduction in the ultimate tensile strength and the maximum strain at fracture, while the yield stress amelioration is more considerable under the compressive monotonic load. In comparison to the monolithic alloy, an improvement was observed in the high cycle fatigue behavior of the composite, which could be attributed to the yield stress enhancement, retarding the crack initiation under the same stress amplitudes.

Permanganate conversion coating is one of the possible alternatives to chromate conversion coating for magnesium (Mg) alloys. Permanganate conversion coating enhances the corrosion resistance of Mg alloys, which is closely related to the thickness and defects of the coating. In this study, the growth kinetics of the permanganate conversion on the LZ91, a dual-phase magnesium alloy, as affected by the bath temperature ranging from 15 to 60 °C, was detailed. The permanganate conversion coating was mainly composed of MnO2/MnOOH and MgO/Mg(OH)2. Increasing the bath temperature reduced the growth rate and thickness of the coating although the bath temperature hardly influenced the composition and crystallinity of the coating. The permanganate conversion coating formed at 15 °C for 10 s was nonuniform with a thickness ranging from 100 to 300 nm, which was prone to cracking after post-coating drying at room temperature. The presence of cracks on the permanganate conversion coating was detrimental to the corrosion resistance. On the other hand, the permanganate conversion coating formed at 40 and 60 °C for 10 s was more uniform with a thickness of less than 100 nm, yet exhibited better corrosion resistance than the counterpart formed at low temperatures (15 and 25 °C).

This study aimed to investigate the impact of building planes on the microstructure and corrosion behaviors of 316L stainless steel (SS) manufactured using selective laser melting (SLM) when subjected to a 0.1 M HCl solution. The investigation of material corrosion behavior involved the utilization of a wide array of surface characterization techniques, as well as various electrochemical measurements. The findings were subjected to a comparison with those obtained from a commercially rolled 316L SS (R 316L SS). The analysis revealed that the XZ and YZ planes displayed a distinctive fish scale melt pool structure, while the XY plane exhibited a columnar melt pool structure. The densities of the low-angle grain boundaries for different building planes were observed as YZ

The present study investigated the inhomogeneity of microstructure and properties of hybrid laser-MIG welded 10-mm-thick 316L/AH36 joints. The study focused on the inhomogeneity of the laser zone, hybrid zone, and transition zone. The temperature field was simulated using ABAQUS and showed a higher cooling rate in the laser zone. As a result, the microstructure in the laser zone was dominated by martensite while that in the hybrid zone was composed of 84 % austenite and 16 % ferrite. The laser zone showed poorer impact toughness and corrosion resistance than the hybrid zone. However, the corrosion resistance of the whole weld was the worst. Because the inhomogeneous microstructure formed a galvanic couple that accelerated the corrosion process. This work indicated that the energy ratio (the ratio of laser to arc energy) should be considered in the welding of dissimilar thick steel to reduce the inhomogeneity in the two zones and obtain a desirable property balance among hardness, toughness, and corrosion resistance.

Zinc (Zn)-based alloys are considered the next-generation biodegradable material for promising bone-implant devices due to their good degradability, formability, and functionality. Nevertheless, the as-cast Zn alloys showed a low strength-toughness, making it challenging to meet the mechanical properties requirements for high-load-bearing bone implants due to their hexagonal close-packed structure, coarse grain size, and less sliding system. Herein, we have developed biodegradable Zn–5Ce alloys by cerium (Ce) alloying followed by hot-rolling, hot-extrusion, and high-pressure torsion (HPT), respectively, for potential bone-implant application. Mechanical testing revealed that the HPT sample exhibited the best mechanical performance matching among the Zn–5Ce samples with a high ultimate tensile strength of ∼345 MPa, yield strength of ∼230 MPa, a moderate elongation of ∼11.4%, and macro-hardness of ∼96.6 HB. Electrochemical corrosion and static immersion testing revealed that the HPT sample showed the highest electrochemical corrosion rate of ∼416 μm/y and degradation rate of ∼43.8 μm/y in Hanks' solution among the Zn–5Ce samples, which is suitable for degradation rate requirements for bone-implant application. Bio-tribological testing revealed that the HPT sample showed high bio-tribological properties matching in Hanks’ solution with the lowest friction coefficients of ∼0.530 and moderate wear loss of ∼2.2 mg. Cytocompatibility and osteogenic differentiation assessment revealed that the diluted extract of the HPT sample showed the highest cytocompatibility towards 3T3 and MG-63 cells and osteogenic differentiation performance towards 3T3 cells among the most diluted extracts. Accordingly, the HPT Zn–5Ce sample is expected to be used for high-load-bearing degradable bone-implant devices, including bone fixation and guided bone regeneration systems.

Cu–Fe composite is a promising candidate for electromagnetic shielding material, while it exhibits poor corrosion resistance due to the different corrosion potential of Fe particles and Cu matrix. In this study, a Cu–Fe composite was processed by multi-directional compression. The effect of multi-directional compression on the mechanical properties of the Cu–Fe composite was evaluated by the tensile test, and the effect of multi-directional compression on the corrosion properties was evaluated by the weight loss test and electrochemical measurement. After 12 compression passes, the yield strength of the Cu–Fe composite is more than two times higher than that of the initial state, and the corrosion rate decreases to nearly half compared to the initial state. Microstructure examination reveals that high density of twin boundaries were generated by multi-directional compression, which could effectively refine the grain size of Cu matrix and improve the strength of Cu–Fe composite. In addition, twin boundaries would reduce the Volta potential difference between Cu matrix and Fe particles, which could effectively inhibit galvanic corrosion, finally leading to a high corrosion resistance of the Cu–Fe composite.

In this study, the mechanical and corrosion characteristics of a corrosion-resistant layer made of stainless steel (STS) 316 L and Fe–Cr–Si alloy powder were investigated using laser-directed energy deposition (DED). In the STS 316 L deposited specimen, both the substrate and deposited layer were face-centred cubic (FCC). The deposited Fe–Cr–Si layer was clearly separated from the substrate because it was composed of body-centred cubic (BCC). Despite the phase differences, the surface of the Fe–Cr–Si-deposited layer showed a lower corrosion rate than that of the STS 316 L. All the deposited specimens exhibited typical high-temperature tensile behavior. However, the Fe–Cr–Si deposited layer at 600 °C showed a notable reduction in strength and increased elongation compared to the room temperature (RT) and 300 °C test results owing to the carbide concentration and phase transformation in the deposited layer. Because nuclear facilities mainly operate at temperatures below 600 °C, Fe–Cr–Si materials can also be used as nuclear piping coating materials. This study provides a mechanism for the high-temperature properties and corrosion resistance of the Fe–Cr–Si deposited layer and makes it competitive for application in fourth generation nuclear power systems.

In this work, the corrosion behavior of pure Mg, Mg3Ag, Mg6Ag, and MgZnYNd alloys in different fixatives (ethyl alcohol (EA), 85 % ethyl alcohol (85 % EA), 10 % neutral buffered formalin (10 % NBF), 4 % glutaric dialdehyde (4 % GD), and 4 % paraformaldehyde (4 % PFA)) was investigated to provide a valuable reference for the selection of fixatives during the histological evaluation of Mg implants. Through the hydrogen evolution test, pH test, and corrosion morphology and product characterization, it was found that corrosion proceeded slowest in the EA and 85 % EA groups, slightly faster in 4 % GD, faster in 10 % NBF, and fastest in 4 % PFA. After corrosion, the EA group surface remained unchanged, while the 85%EA group surface developed minor cracks and warping. The 4%GD fixative formed a dense needle-like protective layer on the Mg substrate. The 10%NBF group initially grew a uniform layer, but later developed irregular pits due to accelerated corrosion. In contrast, the 4%PFA solution caused more severe corrosion attributed to chloride ions. The main corrosion products in the EA and 85%EA groups were MgO and Mg(OH)2, while the other fixatives containing diverse ions also yielded phosphates like Mg3(PO4)2 and MgHPO4. In 4 % PFA, AgCl formed on the surface of Mg6Ag alloy after corrosion. Therefore, to minimize Mg alloy corrosion without compromising staining quality, EA or 85 % EA is recommended, while 4 % PFA is not recommended due to its significant impact.

Ti and Ti-based alloys are increasingly employed as components for various industrial applications, both structural and functional. Forming coatings is one of the potentially highly effective methods to shield products from adverse environmental effects. Among the numerous techniques for forming coatings on Ti and Ti-based alloys, plasma electrolytic oxidation (PEO) stands out. Coatings produced through PEO exhibit high resistance to corrosion, substantial resistance to wear, and strong adhesion to the substrate, which is attributed to the formation of chemical bonds between the underlying material and the coating. Conversely, PEO coatings may not provide sufficient protection for titanium alloys due to the presence of porosity and fine cracks. Establishing an organic film on the PEO coating surface is a potent strategy to seal the defects, thereby inhibiting the intrusion of corrosive elements into the substrate. Applying a polymer layer to the PEO coating could be an effective approach to manage the extent of damage and enhance the resistance to corrosion. This article reviews the latest developments in PEO/polymer composite coatings and investigates the corrosion characteristics of these coatings.

Amorphous magnesium (Mg) alloy, especially Mg–Zn–Ca series, has been receiving continuous attention in biomedical field, because of its favorable corrosion resistance, suitable modulus and biocompatibility. In this work, laser powder bed fusing (LPBF) with unique characteristics of rapid solidification and layer-by-layer fashion was used to fabricate bulk Mg–Zn–Ca and Mg–Zn–Ca–Y amorphous parts. It was revealed that the as-built parts contained amorphous structure, since the molten pool experienced an extremely high cooling rate that suppressed ordered arrangement of atoms. A few of nanocrystals (α-Mg and Ca2Mg5Zn13) were obtained due to repeated heat accumulation in heat-affected zones. More significantly, Y alloying altered the glass forming ability and stimulated in-situ formation of quasicrystal I-phase with high hardness and elastic modulus, which not only acted as reinforced particles, but also retarded the propagation of shear bond and thereby excited the emergence of secondary shear bands and vein patterns. Thus, Mg–Zn–Ca–Y part exhibited simultaneously improved yield strength and plasticity. Despite the micro galvanic corrosion induced by crystalline phases, it exhibited a moderate corrosion rate. Furthermore, in vitro cell tests proved its favorable biocompatibility. Our work highlighted the feasibility to prepare amorphous Mg alloy with controllable performance.

In this study, Keyhole tungsten inert gas (TIG) process, a new variation of traditional TIG process, was performed to weld TC4 titanium alloy with a thickness of 6 mm. The effect of heat input on microstructure and their correlation with mechanical properties and corrosion behavior was studied. The results showed that the microstructure of fusion zone and heat-affected zone changed obviously due to the change of heat input. The microstructure in the joints was transformed from equiaxed primary α and α+β lamellae to complete primary β grains, and then α′ phases were precipitated in the primary β grain. With the increase of heat input, the content and length of the acicular α′ phase grains were increased, resulting in a decrease in the number of high angel grain boundaries (HAGBs). Due to the phase strengthening effect of α′ phases, the microhardness of the joints increased, and the tensile strength increased, reaching a maximum value of 1030.1 MPa when the heat input was 1118 J/mm. The impact toughness of the joints increased firstly and then decreased. The corrosion behavior of the joints was worse than that of the base metal (BM). The best corrosion resistance was obtained when the heat input was 1046 J/mm. It concluded that the excellent comprehensive properties can be obtained when the heat input was in the range of 1046–1118 J/mm.

Improvement of corrosion resistance in high-strength Al–Si–Cu–Mg casting alloy is an important issue for its application in humid and corrosion environment. In this paper, the effect of Cr on microstructure, mechanical properties and corrosion behavior of Al–9Si-1.2Cu-0.5 Mg alloy were investigated. The results indicate that 0.052 % and 0.106 % Cr addition shows a slight strengthening for mechanical properties by introducing AlSiFeCr dispersoids, 0.052 % Cr addition effectively enhances the corrosion resistance of the alloy. The addition of 0.052%Cr not only increase the thickness and stability of the passive film, but also has an obvious effect on the charge transfer process. 0.052 % Cr addition reduces the potential difference between cathode phases and Al matrix. The results of first-principles calculations indicate that the (001) surface of CrO2 would have an effect of adsorbing Cl− ions in the passive film/solution interface, the interaction between Cl and neighboring Cr atoms implies the formation of chemical bonds between Cl atoms and the surrounding Cr atoms at adsorption sites. It contributes to weaken the attack of the passive film by Cl− ions. When Cr level increases to 0.106 %, the appearance of AlSiFeCr dispersoids may result in the additional electrochemical process and weaken the protection on the matrix. This paper designs a novel Al–Si–Cu–Mg–Cr casting alloy with high mechanical properties and high corrosion resistance, expanding automotive industry application of casting aluminum alloy.

This study investigated the influence of adding different titanium contents (0, 3, 6 at. %) and controlling nanoscale L12-type Ni3Ti precipitates through hot-forge and heat treatment on the mechanical and corrosion behavior of FeCoNi medium-entropy alloys. It was found that, when the Ti atom is in a solid solution state, the degree of lattice distortion increases, and the corrosion resistance decreased with increasing Ti content. Whether in the solid solution state or the precipitate state, increasing the Ti content effectively enhanced the strength of FeCoNi alloy. The strengthening effect was particularly prominent in the precipitate state compared to the solid solution state. The experimental results provided valuable references for the design and preparation of other high-strength, tough, and corrosion-resistant multi-principal element alloys.

Post-heat treatment and in-situ rolling, both can be used to improve the coarse grains and anisotropy that are prevalent in metallic materials, fabricated by wire and arc additive manufacturing (WAAM). In this study, the effect of in-situ rolling and heat treatment on the microstructure, mechanical and corrosion behaviors of WAAM 316L was investigated. The results showed that the microstructure of WAAM 316L changed considerably due to the introduction of rolling deformation, as it was observed that the ferrite was distributed in a reticulated or equiaxed morphology instead of dendritic distribution, columnar grains were found to be engulfed, while a large number of low angle grain boundaries (LAGBs) with high dislocation density were introduced. After heat treatment at 650 °C, there was no significant change in grain morphology, ferrite gradually transformed into σ phase, the tensile strength increased, yield strength and elongation decreased. After heat treatment above 1000 °C, the strength and ductility of the rolled WAAM 316L were higher than those of the unrolled WAAM 316L. As the heat treatment temperature increased, the corrosion resistance first decreased and then increased. In-situ rolling resulted in a decrease in the corrosion current density of the steel and also reduced the stability of the passive film.

The corrosion behavior of ship steel with different microstructure in a simulated tropical marine atmosphere was systematically investigated. Results show that homogeneous martensite structure obtained by water-quenching process was much more resistant to corrosion than that of ferrite-pearlite. Furthermore, the precipitation of carbide resulting from tempering process promoted the formation of corrosive microcells within the matrix and further intensified the corrosion. Rapid cooling rate led to the enrichment of chromium, which formed protective corrosion products such as FeCr2O4 and Cr(OH)3. This also facilitated the conversion of α-FeOOH and significantly enhanced the corrosion resistance.

Three different post-heat treatments, including direct aging (DA), solution heat treatment + precipitate hardening (T6), and retrogression and re-ageing (RRA), were carried out on a Si–Zr–Er modified Al–Zn–Mg–Cu alloy, which is manufactured by laser powder bed fusion (LPBF). The results show that direct aging maintains the cellular structure of the as-printed (AP) alloy, while T6 and RRA promoted the damage and decomposition of the cellular structure. The size of the primary Al3(Er,Zr) phase increased after heat treatment, and secondary Al3(Er,Zr) phases were uniformly distributed in the matrix with a size of 5–20 nm. The Mg2Si phase in the DA alloy was a long strip pattern, but uniformly distributed in the T6 and RRA alloy. The ultimate tensile strength of the AP, DA, T6, and RRA alloys reached 468, 474, 389, and 354 MPa, respectively. The size, shape, and distribution of the Al3(Er,Zr) and Mg2Si phases have a significant impact on their corrosion resistance, with the latter having a stronger effect. To sum up, the strength of the DA alloy is increased, but its corrosion performance is decreased with heat treatment. On the other hand, the strength of the T6 and RRA alloys is somewhat sacrificed, but their plasticity and corrosion resistance are significantly enhanced.

The mechanical performance and corrosion behavior are crucial factors for additively manufactured Ti–6Al–4V porous implants, which are influenced by implant design, fabrication method, and post-processing. In the present study, effects of geometrical parameters and heat treatment on the compression and corrosion behaviors of Ti–6Al–4V sheet-based gyroid implants fabricated by laser powder-bed fusion (LPBF) process are investigated. The results showed that an increase in the pore size (ranging from 600 to 1200 μm) did not alter the microstructure, while decreased the Young's modulus and strength of the implants. The post-processing heat treatment resulted in the α' → α + β phase transformation which influenced mechanical properties. The mechanical properties of all scaffolds were found to be comparable to those of human bone. The heat-treated implants showed superior corrosion resistance than the as-built ones. Furthermore, the corrosion resistance of both as-built and heat-treated implants improved with increasing the pore size. The LPBFed Ti–6Al–4V implants with gyroid-sheet structure can be a promising candidate for biomedical implants from both compressive and corrosion behaviors points of view.

The ultra-fine grain structure of Al–Zn–Mg–Cu alloy was prepared by equal channel angular pressing (ECAP) and post cold rolling (CR) combined deformation process. The effect of different rolling deformation on the microstructure, microhardness and corrosion behavior of the ECAP alloy were studied. The results show that with the increase of rolling deformation, the dislocation density increased, the grain and second phases of the deformed alloy were obviously refined. Grain refinement was mainly due to the gradual transformation of some subgrain boundaries and low angle grain boundaries (LAGBs) of deformed alloys into high angle grain boundaries (HAGBs), which eventually form fine grains. The microhardness improvement was attributed to dislocation strengthening, fine grain strengthening and second phase strengthening. Simultaneously, the corrosion behavior of the alloy was tested by immersion corrosion and intergranular corrosion, which revealed that high-density lattice defects, refined grain and second-phase particles can improve the corrosion resistance of the deformed alloys.

Few work have been performed regarding the quantitative characterization of three-dimensional (3D) pitting corrosion process directly, although the corrosion behaviors and the passivation film stability of metals in various solutions have been studied heavily. The reported work quantitatively characterized the 3D pitting corrosion of the Fe-based amorphous alloy coating (Fe-based AAC) via X-ray micro-computed tomography (X-ray micro-CT) and further elucidated the mechanism of its pitting corrosion. Moreover, the microstructure and electrochemical performance of the Fe-based AAC have also been explored. The results showed that the targeted thermal sprayed Fe43Cr20Mo10W4C15B6Y2 coating was prone to be corroded with the increase of the hydrogen ion concentration, i.e. higher hydrogen ion concentration leads to poorer corrosion performance of the Fe-based AAC. The X-ray micro-CT results revealed that the pits in the Fe-based AAC initially nucleated below the pitting potential, and they also generated in the over-passivation stage. Furthermore, it was found that the corrosive medium does not penetrate into the coating/substrate interface, and the deduced corrosion mechanism from the findings was also discussed.