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The probabilistic assessment of failure due to the creep phenomenon must be determined with the minimum deviation. Since the creep failure took years before rupture, laboratory experiments were conducted to represent the failure time. However, the laboratory results are only an empirical approach; therefore, the probabilistic assessment can be deviated. A huge number of variables in creep experiments must be conducted to minimize the deviation. This study investigated the creep strain rate for the 9Cr-1Mo ferritic stainless steel. The lever-arm creep machine was used for the creep rupture test, and the test followed the standard of ASTM E139. The constant loads were applied in the range of 250 – 170 MPa with the homologous temperature of 570 °C. The curve of strain to time was recorded from each constant load condition. The creep strain rate was then calculated and presented in the curve of the creep strain rate to the applied load. The linear regression was drawn from the curve by applying Norton’s equation. By obtaining the creep strain hardening coefficient and exponent, an initial probabilistic assessment of creep failure at a temperature of 570 °C can be predicted.

The in-situ EBSD analysis method was used to systematically study the effect of retained austenite characteristics on the phase transformation behavior of ferritic stainless steel after the quenching and partitioning （Q&P） process. The results show that the phase transformation behavior of retained austenite during deformation is related to its grain size， distribution， and morphology， and its influence degree is arranged in descending order. Compared with inter-martensitic austenite and inter-martensite-ferrite austenite， the trigeminal and twin austenite are more prone to martensitic transformation in the early stage of deformation. This is closely related to the different strains or stresses applied to different distributed retained austenites during deformation. Compared with large-sized austenite， small-sized austenite begins to transform in the later stage of deformation， which is helpful to prolong the uniform elongation. This may be due to the higher interfacial energy and average C content of small-sized austenite， and the need for larger macroscopic stress/strain to induce martensitic transformation due to the strengthening effect of fine grains. The elongated/equiaxed austenite is easy to transform in the early stage of deformation， while the transformation of thin film-retained austenite is mainly concentrated in the later stage of deformation， which is helpful to further improve plasticity. The different transformation behaviors are due to the differences in C and N content， as well as the presence of defects such as stacking faults， dislocations， and slip.

At elevated operating temperatures, a large temperature gradient can cause irreparable damage to the solid oxide fuel cells (SOFCs) stack, eventually interrupting the durability of the stack. Metal substrate support could be used to overcome this challenge. However, the application of metal substrate support poses various challenges such as different thermal expansion coefficients, pore diameters, and complex fabrication techniques. Therefore, a first-ever novel and mechanically strong ferritic stainless-steel metal mesh-supported SOFC design is developed to mitigate these challenges. The metal mesh of 200 μm thickness is laminated with tape-casted green films of anode-support, anode functional layer (AFL), and electrolyte films of SOFC. The iso-static pressure of 300 MPa exhibits a firm attachment of the green films of SOFC with the metal mesh. Subsequently, the metal mesh-supported planar SOFC exhibits 3.3 times higher flexural strength compared to the conventional commercial anode-supported planar SOFC. The nano-CuO is added to constituent layers as a sintering aid to attain the maximum density at a lower sintering temperature of 1100 °C. The result shows that the practical application of the metal mesh-supported cell technology has a great potential to overwhelm the mechanical durability of SOFCs. [ABSTRACT FROM AUTHOR]

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The cold rolling behavior of ferritic stainless steel was investigated via crystal plasticity analysis to clarify the effects of initial orientation and neighboring grain interaction on grain rotation and fragmentation behaviors. The analysis revealed that the {112} < 110 > orientation grain tends to maintain its initial orientation after cold rolling. However, the {110} < 001 > orientation grain completely disappeared at 80% cold rolling thickness reduction. The {110} < 001 > orientation grain had high deformation sensitivity. The four initial orientation grains tend to rotated toward the line connecting < 001 > and < 111 > , eventually stabilizing at < 111 > //normal direction (ND). Grains rotate in the following path: < 117 > → < 113 > → < 112 > → < 223 > → < 111 >. The dislocation density is different between grains near the grain boundary region and those farther away. The near < 111 > //ND deformation microstructure region has a lower dislocation density compared to the region near < 110 > //ND. Furthermore, the {111} < 110 > orientation grain exhibited significant grain fragmentation, while the {001} < 110 > orientation grain eventually forms the < 110 > //rolling direction (RD) deformation microstructure without significant fragmentation. The initial orientation {110} < 001 > grain resulted in a double fiber deformation texture with < 111 > //ND and < 110 > //RD orientations. This grain has grain fragmentation features corresponding to the initial {111} < 110 > and {001} < 110 > orientations. These findings are important for understanding the deformation behavior of grains in polycrystalline materials, as well as for designing high-performance metals by controlling the initial microstructure during cold rolling. [ABSTRACT FROM AUTHOR]

The high‐temperature oxidation behavior of 444 ferritic stainless steel has been studied in cyclic oxidation experiments using synthetic automotive exhaust gas atmospheres at 950 and 1050 °C. The weight gain per unit area of the 444 ferritic stainless steel following oxidation at 950 °C for 100 h iss 85.7% lower than recorded at 1050 °C. The oxide scale at both temperatures consisted of Fe–Cr and Mn–Cr spinels in the outer layer and Cr2O3 in the inner layer. Nodule formation and spallation of the oxide scale are identified as the main causes of breakaway oxidation. The depth of the internal oxides gradually increases with the oxidation time. The nucleation and growth of internal SiO2 result in the formation of metal protrusions, which are eventually consumed in the formation of a SiO2 layer. The SiO2 layer is formed at the interface between the oxide scale and the substrate at 1050 °C. The nucleation and growth of internal SiO2, in combination with lateral growth of SiO2 at the Cr2O3 layer/substrate interface contributed to the formation of the SiO2 layer. [ABSTRACT FROM AUTHOR]

In order to enhance the formability and ridging resistance of Sn microalloyed ferritic stainless steel (FSS), an investigation was conducted on the texture and microstructure evolution, as well as formability and surface ridging of Sn microalloyed FSS at various hot rolling finishing temperatures (HRFTs). This study employed x-ray diffraction, optical microscopy, electron backscattering diffraction, tensile testing, and surface roughness measurement techniques. Hot-rolled sheets with HRFTs of 940, 870, 800, and 730 °C were subjected to annealing at 950 °C for 5 min and cold rolling at a reduction of 80%. Subsequently, they were annealed at 900 °C for 2 min. The research indicates that decreasing the HRFT has a positive impact on reducing {001} <110> grains and its texture intensity. Additionally, it leads to microstructure refinement and intensification of <111> //ND (ND: normal direction), thereby improving formability and resistance against ridging. When the HRFTs are within the range of 940–730 °C, the final sheet with an HRFT of 800 °C exhibits optimal formability and surface quality due to the formation of fine recrystallized <111> //ND grains with a sharp texture intensity. In comparison to the final sheet produced through conventional hot rolling with an HRFT of 940 °C, the average r value for the final sheet with an HRFT of 800 °C is increased by 19.4%, while the ridging height is reduced by 46.5%. This demonstrates the significance of reasonable optimization of the hot rolling process in enhancing the formability and ridging resistance of Sn microalloyed FSS. [ABSTRACT FROM AUTHOR]

Exhaust gas recirculation (EGR) coolers are standard accessory items to reduce internal combustion engine emissions and fuel consumption. These coolers are composed of stainless steel brazed with Ni-based brazing filler metals that can internally withstand high exhaust gas temperatures and corrosive environments. In this study, the corrosion behavior of the SUS444 joint brazed with MBF67 foil was examined by an anodic polarization measurement in hydrochloric acid and was compared with that of the SUS444 joint brazed with MBF20 foil. The result indicated that the SUS444 joint brazed with MBF67 showed corrosion with a much higher potential in the polarization curve than the SUS444 joint brazed with MBF20. The reason for the high potential was concluded that the Cr-depleted zone was not formed at the boundary layer between the SUS444 and MBF67 because of low B in MBF67, and the high phosphorus--containing (Ni, Cr)-P eutectic phase with high corrosion resistance remained at the brazed layer because of high P in MBF67 [ABSTRACT FROM AUTHOR]

In this study, an integrated crystal plasticity and cellular automaton (CA) model has been developed and employed to investigate the processes of cold rolling and annealing in ferritic stainless steel. Crystal plasticity simulates the deformation microstructure, deformation texture and corresponding dislocation density distribution in the cold rolled ferritic stainless steel. Meanwhile, CA predicts the microstructural evolution originating from nucleation and growth. The resolution of the crystal plasticity model has been improved using a newly developed remeshing technique, which allows for the capture of the grain substructure in the deformation microstructure. The developed model has been validated by experimental measurements with electron backscatter diffraction (EBSD) in terms of comparing the orientation distribution functions (ODFs), misorientation, local substructures, and grain size. The good agreement between simulations and experiments indicates that the developed crystal plasticity with CA model is reliable and efficient for predicting the microstructure and texture evolutions during cold rolling and subsequent annealing.

Three different approaches to control the phase formation in powder bed fusion - laser beam (PBF-LB) printing using a powder mixture of duplex stainless steel (DSS) 2507 and austenitic stainless steel 316 L were examined: (i) in situ solid state reheating, (ii) utilization of an island scan strategy, and (iii) switching process parameters between layers of a build. Analytical modeling was used to determine the time-temperature profiles during each of these processes, and was combined with thermodynamic simulations through Thermo-Calc to predict and explain the phase formation measured experimentally. It was found that the reheating from additional layers was critical to the nucleation of austenite, even with the increased Ni content in powder mixtures. This was evident in the island scan strategy prints where the corners of the islands showed significantly less austenite (∼45%) as compared to the centers of the islands (∼96%), as well as in the multi-layer samples where alternating laser power for fixed chemical composition of powder mixture resulted in varying content from ∼75% (lower power) to ∼90% (higher power). Additionally, in situ reheating using a lower power laser was capable of minimally increasing the austenite content layer-by-layer, by raising the temperature of the layer above the nucleation temperature of austenite. These results showcase the capability of PBF-LB to manipulate phase structure in ways not possible through traditional manufacturing techniques, as well as the ability of Thermo-Calc to accurately predict the trends observed that can be applied to other alloy systems.

Agricultural activities such as grain processing play a crucial role in Brazil's economy, contributing significantly to its gross domestic product (27.4% in 2021). The use of carbon steel equipment leads to considerable environmental and economic losses in agribusiness due to corrosion. This study explores the erosion-corrosion behavior of a dual-phase 11Cr and an 18Cr8Ni stainless steel (SS), compared to a mild (ASTM A36) and a high-strength carbon (AHSS) steel under conditions close to the agribusiness reality. The impact of corn particles as erosive component associated to pure water and chloride-containing environments was studied using a fog chamber, a topic until now unexplored in the literature. The methodology adopted is novel and explores the erosion-corrosion synergy in cumulative steps, aiming to shed light on the mechanisms of corrosion and wear that affect the materials in the agribusiness industry. The findings reveal that corn particles, despite their soft nature, can easily remove non-adherent corrosion products from the steel surface. In the deionized water medium, the impact of the soft particles can also shift the corrosion pattern of advanced high-strength steels from general corrosion to localized pitting damage reduzing the corrosion rates. The carbon and 11Cr steels showed the highest corrosion rates under the pure corrosion condition in both media. The erosion-corrosion process considerably reduced the corrosion rate, mainly in the deionized water medium for the carbon steels. An exception to this behavior was 18Cr8Ni steel, whose corrosion rates, however, were the lowest among the materials. Low-chromium stainless steel emerges as a cost-effective solution to erosion-corrosion challenges in the agribusiness segment.

In this study, the microstructural evolution and mechanical behavior of AISI 430 ferritic stainless steel produced by cold single-roll drive rolling were investigated. By increasing the rolling deformation, the width of the grains decreased, and after 60% rolling, highly elongated ferrite grains and shear bands occurred in the microstructure. With the increase in the strain, first, the shear texture and then the deformation texture were strengthened in the samples. Dislocation density increased with increasing strain, which led to increasing the macro and microhardness. Also, the up and down surfaces of the sample had different hardness values due to being exposed to two rolls with different speeds. The 60% rolled sample had the highest yield strength (823 MPa), the highest ultimate tensile strength (833 MPa), and the lowest ductility (10.7%), which was due to increasing dislocation density and shear bands. After 60% rolling, the number, size, and depth of dimples decreased compared to the initial steel. However, the fracture mode of all deformed samples was ductile.

Due to the recurrent starting and stopping operations of automobiles during service, their engines' hot ends are continually subjected to high-temperature cyclic oxidation. Therefore, it is crucial to develop ferritic stainless steels with better high-temperature oxidation resistance. This study focuses on improving the high-temperature cyclic oxidation performance of 18Cr-Mo (444-type) ferritic stainless steel by alloying with high-melting-point metal W and the rare earth element Ce. For this purpose, a high-temperature cyclic oxidation experiment was designed to simulate the actual service environment and investigate the high-temperature cyclic oxidation behavior and microstructure evolution of 444-type ferritic stainless steel alloyed with W and Ce. The oxide structure and composition formed during this process were analyzed and characterized using scanning electron microscopy/energy dispersive spectroscopy (SEM-EDS) and electron probe X-ray micro-analyzer (EPMA), in order to reveal the mechanism of action of W and Ce in the cyclic oxidation process. The results show that 18Cr-Mo ferritic stainless steel alloyed with W and Ce exhibits an excellent resistance to high-temperature cyclic oxidation. The element W can promote the precipitation of the Laves phase between the matrix and the oxide film, and the small-sized Laves phase can inhibit the interfacial diffusion of oxidation reaction elements and prevent the inward growth of the oxide film. The element Ce can refine oxide particles and reduce the thickness of the oxide film. CeO2 particles within the oxide film can serve as nucleation sites for the formation of oxide particles from reactive elements, and they also contribute to pinning the oxide film, thereby enhancing its adhesion. [ABSTRACT FROM AUTHOR]

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In the companion paper, test results were presented to explore the flexural performance of cold-formed ferritic stainless steel (FSS) closed built-up beams. Each specimen was fabricated by joining two lipped channels in a face-to-face configuration and securing them with spot welds at intermediate points along the beam span. Sectional aspect ratio, compression flange's sectional slenderness and moment gradient were the key parameters varied to explore their influence on the flexural response of such members through tests. The current paper establishes a simplified finite element (FE) model of cold-formed FSS closed built-up beams and verifies it against the test results. Further, an extensive parametric study is carried out using the validated FE model to generate a large pool of data points. A wider database comprising of test results, numerical results obtained from this study and numerical results available in the companion paper were used to critically examine the adequacy of the current Australian Specifications (AS/NZ), American Standard (SEI/ASCE-8), European Code (EN 1993-1-4), Modified Eurocode approach suggested by Gardner and Theofanous, and Direct Strength Method (DSM) in North American Specification (AISI-S100: 2016), Modified DSM approach proposed by the authors in the literature and Continuous Strength Method (CSM) for cold-formed steel (CFS) flexural members. This makes the current study the first to extensively assess the accuracy of the various design guidelines available in the codes and other relevant literature, which explicitly highlighted their grave limitations. Accordingly, through suitable modifications and recommendations, new design rules are proposed to reliably and safely predict the flexural capacity of cold-formed FSS closed built-up beams. [ABSTRACT FROM AUTHOR]

Stainless steel is used as a heat-resistant material not only in air, but also in carburizing atmospheres containing CO and CO2. Carburization may cause austenization for ferritic stainless steels. In this study, the high-temperature oxidation behaviors of 17％ Cr ferritic stainless steels with and without the addition of austenite-forming elements, such as Cu and Ni, in a carburizing atmosphere at 1123K were investigated. The steels did not exhibit breakaway oxidation in the temperature range of 1123-1273K in air. However, doping the steels with Cu and Ni enhanced breakaway oxidation in a carburizing atmosphere at 1123 K. Traces of austenization and carburization were observed at the base metal under the breakaway oxidation scale of the 17％ Cr steel doped with 1％ Cu and 1％ Ni. Thus, it is proposed that the breakaway oxidation of the ferritic stainless steels in a carburizing atmosphere is attributed to austenization induced by carburization and doping with austenite-forming elements. [ABSTRACT FROM AUTHOR]

Copyright of Iron Steel Vanadium Titanium is the property of Iron Steel Vanadium Titanium Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present research used the DC electrodeposition method to apply an Mn–Co–ZrO2 composite coating on the steel interconnect plates of solid oxide fuel cells. The surface morphology and phase structure of the obtained coating were investigated using a field emission scanning electron microscope (FESEM) equipped with an EDS analyzer and an XRD device, respectively. The isothermal oxidation behavior of the samples was also studied by measuring their weight changes after 500 h oxidation at 800 °C. The results of isothermal oxidation showed that the oxidation rates of the coated and uncoated samples were of the order of 10−14 g2 cm−4 s−1 and 10−13 g2 cm−4 s−1, respectively. XRD analysis confirmed the presence of highly electrically conductive spinels (MnCo2O4 and Co3O4) and ZrO2 particles in the oxidized coating. In contrast, it proved the presence of spinels with low electrical conductivity (FeCr2O4 and MnCr2O4) in the oxide scale on the uncoated sample. [ABSTRACT FROM AUTHOR]

Ferritic stainless steel is essential in many industries due to its corrosion resistance advantages over austenitic stainless steels. However, it is susceptible to embrittlement caused by factors such as grain growth, sigma phase formation, and carbide precipitation. This study investigates the stress corrosion cracking (SCC) behavior of AISI-409 ferritic stainless steel welded with AWS E316LT1-4 flux-cored wire, with heat inputs ranging from 400 J/mm to 805 J/mm. SCC tests were conducted by applying a constant load, followed by mechanical and microstructural analysis upon failure. Interestingly, higher heat input exhibited superior SCC resistance despite slower cooling rates compared to lower heat input. SCC initiated in the heat-affected zone (HAZ) and extended into the ferritic region. Photomicrographs depicted a ductile-to-brittle transition with reduced elongation values. Two distinct fracture regions were observed: dimples and cleavage facets, indicative of SCC-induced brittle fracture behavior. These findings provide insights into the SCC behavior of ferritic stainless steel, guiding the development of more resilient, corrosion-resistant materials for various industries.

Ferritic stainless steels have been utilized in marine atmosphere and are found to be susceptible to pitting corrosion in our field investigation. Alloying is an important to modify the passive film on the surface and improve the pitting corrosion resistance. Nevertheless, how the addition of titanium modifies the passive film and affects the pitting corrosion resistance of ferritic stainless steels remain controversial. This study has elucidated these topics through microstructure analysis and corrosion properties analysis. The results demonstrate that titanium addition increases the pitting potential almost linearly. Titanium forms TiO2 in the passive film and reduces defect density of the passive film. Moreover, titanium addition induces the precipitation of the Laves phase, which promotes micro-galvanic corrosion. For the titanium-alloyed ferritic stainless steels, pitting corrosion predominantly occurs in the ferrite phase adjacent to the Laves phase. The influence mechanism of titanium on the pitting corrosion of the ferritic stainless steel has been established, which takes micro-galvanic corrosion induced by titanium addition into account.

The precipitation behavior of Nb-rich phase in Al-free and 1Al Nb-bearing ferritic stainless steels (FSSs) at 700 °C were investigated. The results show that Nb-bearing carbides and Laves phases with mutual transformation relationships are precipitated in both Al-free and 1Al Nb-bearing FSSs at the early stage of aging. At this stage, the coarsening rate of Laves phase is higher than that of Nb2C phase, and the addition of Al can promote the precipitation of Laves phase and weaken the precipitation of (Nb, Ti)2C phase. As the aging time extended to 60 min, the Nb-rich phase in the two experimental steels was mainly Laves phase, and the intragranular Laves phase showed feather like aggregation distribution. On the one hand, the added Al can be enriched in the Laves phase to produce a tailing morphology, on the other hand, it can reduce the diffusion rate of Nb atoms in the matrix, thereby weakening the aggregation state of the intragranular Laves phase. During the coarsening process of Laves phase, the addition of Al can reduce the coarsening rate of Laves phase by 7.45 times.

Cr-Ni resource-saving Sn-containing ferritic stainless steel (FSS) was taken as the research object. The microstructure evolution and properties change of the experimental steel under different hot rolling processes were explored by means of optical microscope(OM), electron backscattering diffraction(EBSD), X-ray diffraction(XRD), room temperature tensile test, electrochemical corrosion test, etc. The results show that when the finishing rolling temperature (FRT) is in the range of 940-730 ℃, properly reducing the FRT has a significant role in refining the grains of hot-rolled and annealed sheets and final cold-rolled and annealed sheets, as well as increasing the orientation density of recrystallization texture, and thus the yield strength, tensile strength and elongation are significantly increased. When the FRT is 800 ℃, the tensile strength is 509 MPa, the yield strength is 331 MPa, and the elongation reaches a maximum of 42%, and meanwhile, the maximum cupping value and plastic strain ratio are obtained, leading to the best mechanical properties. In addition, the pitting potential and self-corrosion potential are increased, while the corrosion current density and corrosion rate are decreased by properly reducing the FRT. When the FRT is 800 ℃, the pitting potential reaches the maximum, the corrosion current density reaches the minimum and corrosion rate reaches the lowest, thus the optimum corrosion resistance is obtained in the steel. The properties of Sn-containing FSS are significantly improved compared with SUS430 FSS by optimizing the hot rolling process.

An important aspect of energy conservation and emission reduction in automotive industry is to improve the combustion efficiency of gasoline. The full combustion of gasoline will inevitably cause an increase in exhaust temperature. The coarsening and dissolution behavior of precipitates in steel will lead to a decrease in its high-temperature mechanical properties when the engine is used for a long time in such an alternating heating and cooling environment. In order to obtain ferritic stainless steel with good high-temperature resistance, this paper is based on 444 ferritic stainless steel and attempts to partially replace Mo element with W element to obtain Laves phase containing W, Mo, and Nb with more stable high-temperature performance. A simulated cyclic high-temperature annealing process up to 1050 °C was designed to investigate the precipitation behavior in this modified ferritic stainless steel. The results show that using W to replace Mo in 444 ferritic stainless steel can refine the grains of ferritic stainless steel. It can not only provide better solid solution strengthening at elevated temperature, but also stabilize the Laves phase and provide precipitation strengthening. The reason is that the W elements can change the composition of the Laves phase in ferritic stainless steels and precipitate Fe2(Nb, W) with high thermal stability to provide stable precipitation strengthening during long-term alternating annealing. The W-rich Laves phase is prone to precipitation at grain boundaries, effectively pinning grain boundaries and preventing microcracks from propagating along grain boundaries during service, thereby improving the service life of the steel.

The research investigates the mechanical and corrosion behavior of Cr-Si-S-C ferritic stainless steel (FSS), known as EN1.4105, which is equivalent to AISI430F. The static isothermal recrystallization annealing is applied to the cold-drawn (CD) materials with two different reduction rates (RRs) of 20 and 35%, under various conditions of soaking temperature and incubation time, which provide 42 unique specimens. The microstructures of CD and annealed materials are characterized by using the electron backscatter diffraction method. X-Ray diffraction analysis alongside scanning electron microscopy linked with energy-dispersive X-ray spectroscopy are also employed to scrutinize the precipitation of any secondary phases, morphologies, and the related chemical compositions. Two different corrosive chlorinated and acidic electrolyte solutions are used for the potentiostatic-based corrosion tests to investigate the passivation kinetics. The results show that the higher RR, which provides faster recrystallization, results in a higher scale of non-hardenable materials. In addition, the effects of RR and annealing conditions are found to have an impact on the corrosion resistance. Moreover, the material exhibits varied behavior in terms of both passivation layer formation as the immersion in the sulfuric acid electrolyte solution (SAES) and active electrochemical behavior immersing in sodium chloride electrolyte solution (SCES). However, this material shows lower corrosion current density and higher corrosion potential in the SCES compared to the SAES medium. The comprehensive findings underscore the intricate relationship between reduction rates, annealing conditions, microstructural evolution, and corrosion behavior in this FSS. The observed trends provide valuable insights for optimizing material performance and corrosion resistance in practical applications. [ABSTRACT FROM AUTHOR]

Ferritic stainless steel (FSS) is widely used to manufacture deep-drawn products for corrosion resistance applications, being the alloy drawability strongly affected by its microstructural anisotropy. This study combines a variety of microscopy techniques enabling in-depth analyses of the microstructural evolution of two different FSSs correlated to their deep drawing performance. One of the steels has a good correspondence with the standard EN-1.4016 (AISI 430). The other is a modified version of the previous one with higher contents of the ferrite-stabilising elements Si and Cr, and lower contents of the austenite-stabilising elements C, N, and Mn. Electron Backscatter Diffraction results confirm that the microstructural properties and drawability of FSS in the deep drawing process are improved in the modified steel version. Scanning transmission electron microscopy under low-angle annular dark field conditions evidences that the deformation mechanism of FSS during deep drawing follows a microstructural distortion model based on the grain size gradient and shows a variation of the deformation texture depending on the alloy composition. This work demonstrates the potential of advanced microscopy techniques for optimising the processing and design of ferritic stainless steels, with slight variations in the alloy composition, for deep drawing applications. [ABSTRACT FROM AUTHOR]

The rolling process is crucial in the process design for achieving good formability of ferritic stainless steel. A comparison is made between hot rolling and cold rolling, and the influence of reduction distribution between hot and cold rolling on the evolution of microstructure and texture is discussed. The results indicate that the partitioning of a high cold-rolling reduction rate is better than the hot rolling in terms of microstructure and properties. With increasing thickness reduction via cold rolling, {223}<110> component in cold-rolled sheets exhibits a progressive strengthening, while {111} <121> component becomes more intense and the degree of deviation from the ideal γ-fiber axis is weakened after annealing. The increase in cold deformation refines the microstructure and increases the fraction of <111> //ND-oriented grains. Therefore, ferritic stainless steels with higher cold-working render an excellent combination of strength and formability. [ABSTRACT FROM AUTHOR]

The oxidation kinetic behavior of Crofer22H alloy at 700–800 °C was investigated. Due to the high oxidation rate exhibited at 800 °C, the xCr-MnCo dual-structured spinel coating was prepared by magnetron sputtering. The element diffusion behavior of the coating/alloy system was changed by control the formation of Cr layer with different thicknesses on the surface. Appropriately increase the thickness of Cr barrier layer can effectively hinders the Fe outward diffusion and improve the antioxidant performance. Fe doped into Mn–Co spinel increased the electron hopping in the crystal structure. Higher electron hopping and thin Cr 2 O 3 layer reduced the electron resistance. • A new xCr-MnCo dual-structured coating was proposed on Crofer22H interconnect. • The Cr barrier layer effectively inhibits the Fe outward diffusion from the alloy. • The spinel coating significantly reduces the oxide layer area specific resistance. • Revealed the oxidation and electrical conductivity mechanism of the coating. [ABSTRACT FROM AUTHOR]

More and more cars are installing urea selective catalytic reduction (SCR) systems to solve the problem of exhaust emissions, which often operates at high temperatures in the exhaust system and is prone to failure of the exhaust pipe due to high-temperature oxidation. And niobium containing ferritic stainless steel has been widely used in the manufacturing of automotive exhaust pipes. In order to extend the service life of ferrite stainless steel exhaust pipes, niobium plays a crucial role as an added alloying element. The solid solution and precipitation of niobium in ferritic stainless steel will give ferritic stainless steel more excellent high temperature resistance. The precipitation of Nb can change the organizational structure in steel and refine the grains. However, if the content is not properly controlled, large particles of (Nb, Ti) C will precipitate, which will reduce the high temperature oxidation resistance. In this paper, the high temperature oxidation behavior of two kinds of ferritic stainless steels with different Nb content at 700 °C, 800 °C and 900 °C was studied. The microstructure of the oxide film on the surface of the material, the thickness of the oxide layer on the cross section, the distribution of chemical composition, the existence form and distribution of Nb element were analyzed by SEM, EDS, XRD and TEM. The results show that the higher the niobium content, the better the high temperature oxidation resistance, and the higher the temperature, the more obvious the high temperature oxidation resistance of niobium. This is because the high Nb content steel is easy to precipitate NbN and other Nb-containing precipitates at the grain boundary, which is helpful to the high temperature resistance. In the case of less Nb content, its ability to generate (Nb, Ti) C precipitates and coarsen at high temperatures reduces its high-temperature resistance. [ABSTRACT FROM AUTHOR]

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The powder bed fusion–laser beam (PBF-LB) process, a method of additive manufacturing (AM), was used to print duplex stainless steel (DSS) using commercial-grade 2507 powders. While conventionally processed DSS has a two-phase microstructure consisting of 50% austenite and 50% ferrite, the PBF-LB-printed 2507 alloy was nearly 100% ferrite. Optimal processing conditions that minimized porosity were determined to be 290 W laser power and 1000 mm/s scan speed, and grain size, texture, and phases were characterized as a function of laser power and scan speed. Grain size increased with increasing laser power but decreased with increasing scan speed. A <100> texture diminished with increasing scan speed from 1000 mm/s to 1400 mm/s. No austenite phase was detected. Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) characterization revealed nanoscale chromium nitride precipitates in the ferritic matrix (incoherent hexagonal close-packed (HCP) precipitates at grain boundaries and coherent body-centered cubic (BCC) precipitates within the grains) and a high density of tangled dislocations. Tensile tests of as-printed alloys showed a yield strength of 570 MPa, an ultimate tensile strength of 756 MPa, and an elongation to failure of 10%. The tensile properties were analyzed based on the observed microstructure considering grain size, nanoscale precipitates, and the high density of dislocations. [ABSTRACT FROM AUTHOR]

A self-designed ultrasonic-assisted welding platform was built to improve the poor microstructure and properties of conventional TIG welded ferritic stainless steel. The ultrasonic vibration was transmitted to the weld pool through the base metal in the manner of point–surface contact in the optimal position after calculation. The results show that the coarse columnar grains in the welded joint can be transformed into very fine equiaxed grains under ultrasonic vibration, especially the coarse columnar grains near the fusion line where cliff-like refinement occurs. The maximum grain size in the weld seam is reduced from 420 μm to 260 μm, and the average size is reduced by 60%. At the same time, the grain orientation tends to be harmonized. The microhardness of the welded joint is greatly improved on the whole, and the softening of the heat-affected zone caused by grain coarsening is effectively inhibited. Compared with the welded joints without ultrasonic assistance, the tensile strength and yield strength can be increased by 61 MPa and 47 MPa, respectively, under 130 W ultrasonic vibration. By strengthening the weak part of the welded joint, the weldability and toughness reserve of 441 ferritic stainless steel can be significantly improved. [ABSTRACT FROM AUTHOR]

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The “Gold Dust Defect” that sometimes appears on the surface of the AISI 430 ferritic stainless steel has been related to an improper recrystallization of the material. Hot-rolling, a decisive step in the production process, seems the step where this defect is induced and temperature during this treatment plays a key role. To trace back the origin of this defect, the microstructural evolution of a sample of an AISI 430 was monitored at the different stages in the production process of the steel. In particular, a detailed study combining electron backscatter diffraction with other techniques, such as optical microscopy and scanning electron microscopy has been performed. The whole set of results evidences that after hot-rolling and subsequent annealing, the material contains a large amount of martensite in the center of the cross-section due to a fast cooling of the austenite originated during rolling. In addition, the surface shows a top-layer made up by unrecrystallized subgrains separated from the matrix by an accumulation of chromium carbides. After pickling, the top-layer of subgrains semi-detaches from the surface forming flakes which cannot recrystallize. Most of these flakes do not peel off during the subsequent stages but survive until the end of the production process, forming Gold Dust Defect flakes.

The current work investigates the relationship between the crack growth rate (CGR) and the cyclic crack‐tip opening displacement (ΔCTOD) of microstructurally small fatigue cracks by using high‐resolution digital image correlation (DIC). Load‐controlled fatigue tests were conducted on small‐scale specimens of 18%Cr body‐centered cubic ferritic stainless steel. Microstructurally small fatigue crack growth was analyzed based on accurate high sample‐rate measurements, starting from a sub‐grain crack length up to seven times the volume‐weighted grain size dv = 224 μm. Under these experimental conditions, the high‐resolution analyses reveal that variation from the otherwise linear relationship between CGR and ΔCTOD on double logarithmic scale is due to the crack‐tip bypassing an inhomogeneous shear strain localization zone. In this zone, ΔCTOD is not able to characterize the behavior of microstructurally small fatigue cracks. Outside the shear strain localization zone, ΔCTOD still is a valid crack driving force parameter. Highlights: Crack tip opening displacement range ΔCTOD and CGR show mostly linear relationship.ΔCTOD and CGR relationship becomes non‐linear if shear strain accumulation is present.If the crack tip penetrates the hardened region, CGR decreases.Strain accumulation is influenced by grain orientation and grain size. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)