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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.

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.

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]

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]

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic 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.)

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.)

The plasticity of welded 441 ferritic stainless steel joints was controlled by varying the laser beam spot diameter during laser welding. A stainless steel plate thickness of 1.2 mm was used. The microstructures of the welded joints were analyzed for various spot diameters. The elongation of breaks and the reduced area of tensile specimens were analyzed to study the effects of spot diameter on plasticity of the welded joints. The results showed that the weld melt width and weld column crystal size increased with the spot diameter, but isometric crystals in the center of the weld were gradually reduced. Increasing spot diameter resulted in decreased tensile strength, elongation after breaks, and area reduction. So the parameter must be controlled during the laser welding. [ABSTRACT FROM AUTHOR]

The effects of alloy elements (Cr, Mn, Cu, Si, Al, Ni, and Ce) on the anti-corrosion behavior and soft magnetic properties of ferritic stainless steel were studied. The results show that the increasing content of Cr, Mn, Cu, and Si ameliorate anti-corrosion behavior, and among the alloy elements, Cu is the most effective to enhance corrosion resistivity. Conversely, the anti-corrosion performance deteriorates with increasing Al and Ce content, despite still maintaining good corrosion resistance overall. Furthermore, in regard to the soft magnetic properties, the regulatory mechanism is more complex and the addition of Cu, Si, and Ce can improve the soft magnetic properties, while their content should be limited. The augmentation of Cr deteriorates the soft magnetic properties, while the increase of Al proves advantageous. Meanwhile, Ni is effective to improve the soft magnetic properties; however, it does not significantly enhance the corrosion resistance, and considering its cost, it is not a necessary element to add. With the optimal composition, the alloy exhibits superior anti-corrosion behavior and softer magnetic properties compared to the commercial grade steel, which can contribute to expanding the applications of ferritic stainless steel. [ABSTRACT FROM AUTHOR]

In this study, the effect of cold rolling reduction ratio (CRRR) on the microstructure and mechanical properties of ferritic stainless steel (FSS) 430 were analyzed based on a series of experiments. The results show that the thickness of coarse grain bands decreases with an increase in CRRR, and when the CRRR increases to a certain value, the coarse grain bands break down into refined, equiaxed grains due to the plastic deformation. In addition, the optimization of CRRR was found to benefit both the microstructural refinement and mechanical properties of FSS 430. Also, the optimization of CRRR optimized the texture structure of FSS 430 by reducing the fraction of undesired components ({110} < 110 > component, for example), giving a rise to the plasticity of material. On the other hand, the formation of Lüders band can also be affected by the modification of CRRR. Overall, an optimal CRRR of 70% was obtained with refined microstructure and texture structure, thereby improving the mechanical properties of FSS 430. [ABSTRACT FROM AUTHOR]

The "gold dust defect" (GDD) appears at the surface of ferritic stainless steels (FSS) and degrades their appearance. Previous research showed that this defect might be related to intergranular corrosion and that the addition of aluminium improves surface quality. However, the nature and origin of this defect are not properly understood yet. In this study, we performed detailed electron backscatter diffraction analyses and advanced monochromated electron energy-loss spectroscopy experiments combined with machine-learning analyses in order to extract a wealth of information on the GDD. Our results show that the GDD leads to strong textural, chemical, and microstructural heterogeneities. In particular, the surface of affected samples presents an α-fibre texture which is characteristic of poorly recrystallised FSS. It is associated with a specific microstructure in which elongated grains are separated from the matrix by cracks. The edges of the cracks are rich in chromium oxides and MnCr2O4 spinel. In addition, the surface of the affected samples presents a heterogeneous passive layer, in contrast with the surface of unaffected samples, which shows a thicker and continuous passive layer. The quality of the passive layer is improved with the addition of aluminium, explaining the better resistance to the GDD. [ABSTRACT FROM AUTHOR]

A novel approach was proposed to elucidate hot flow stress of ferritic and austenitic duplex alloys by employing ferritic stainless steel in the duplex temperature range. Hot compression tests of 16%–18% Cr stainless steel were conducted in the temperature range from 823 °C to 1250 °C. SUS430 in this temperature range can be used to investigate the flow curve of the austenite–ferrite coexisting state and ferrite single-phase regions above and below the duplex temperature. The hot deformation behavior in the α-single phase (body-centered cubic, ferrite) region of SUS430 was compared with SUS430LX and found to be equivalent. The form of the flow curve identified by the inverse analysis to correct for temperature and deformation inhomogeneities during the compression tests changed owing to the presence of the γ-phase (face-centered cubic, austenite), which was not visible in the axial stress–strain curve obtained by the hot compression tests. The obtained flow stress parameters were subjected to regression analysis, which made it possible to describe quantitatively the effects of γ-phase precipitation on the flow curve. Observations of the internal microstructure revealed the differences in deformation mechanisms of the α-single phase and the α+γ duplex region. • Hot flow stress of duplex region in ferritic stainless steel was studied. • The inverse analysis of the compression test clarified changes in flow curve. • The flow curve changed owing to the γ-phase in α+γ duplex region. • The effects of γ-phase precipitation on the flow curve were described quantitively. • The deformation mechanisms in α-single and α+γ duplex regions were elucidated. [ABSTRACT FROM AUTHOR]

The effect of annealing temperature on the microstructure, mechanical property and anti-corrosion behavior of the X2CrNi12 ferritic stainless steel were systematically investigated. The results demonstrate that a large amount of (Fe, Cr)23C6 precipitated at the ferrite grain boundaries after annealing below 740 °C. The precipitation of the (Fe, Cr)23C6 was prevented with the increase of annealing temperature, and the martensite content gradually increased, which improved the tensile strength, yield strength, and hardness of the steels, while the elongation was decreased. The best comprehensive mechanical properties can be obtained at the annealing temperature of 850 °C and 950 °C. The ductile-dimple fracture is the primary fracture mode for the steels. The corrosion rates of the stainless steels first decreased and then increased with the increase of annealing temperature. The 770 °C-annealed steel has the best anti-corrosion ability. The corresponding corrosion mechanism can be attributed to the pitting corrosion induced by the (Fe, Cr)23C6 and martensite. Moreover, the precipitation of (Fe, Cr)23C6 could consume the Cr in the matrix and prevent the formation of passive film on the surface. And the phase transformation stress in the martensite can accelerate the local corrosion of the steel matrix.

The process of autogenous laser welding of stainless steel X2CrTiNb18 was investigated. The Yb:YAG disk laser was used in the study for welding of 1.5mm thick butt joins. The influence of basic laser welding parameters on the joint quality, fusion zone geometry, microhardness distribution across the butt joint, structure and microstructure of fusion zone (FZ) and heat affected zone (HAZ) was studied and determined. The quality level of the test joints was determined according to the PN-EN ISO 13919-1 standard. The chemical composition of the base metal was determined by spark emission spectroscopy. Results of the study have shown that laser welding parameters have a significant influence on the quality of butt joints. However, it is possible to produce joints that meet the high requirements and criteria of quality. The width of HAZ of the butt joints welded in the investigated range of parameters was narrow and did not exceed 0.2 mm. It was found that the most common imperfections of the analysed joints are concavity of the weld face and insufficient penetration. The HAZ region of joints is characterized by mainly ferritic microstructure with complex carbides precipitates. In turn, the fusion zone is dominated by a ferritic microstructure but also precipitates were observed, which were identified as fine dispersion carbides. Hardness of the base metal is round 160÷170HV0.3. A tendency to increase in hardness in the HAZ and FZ was observed. The maximum hardness measured in HAZ was approx. 220HV0.3, while in the FZ 190HV0.3. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) techniques such as laser powder bed fusion (L-PBF) are rapidly growing due to the inherent design freedom and possibilities to produce components not available with other techniques. This could be utilized in, e.g., the design of new types of heat exchangers in ferritic stainless steels often used for high-temperature applications. Ferritic stainless steels are, however, difficult to weld and could therefore imply obstacles when produced by AM. When establishing the AM-produced alloy in new applications, it is therefore important to increase the understanding of the mechanical properties and high-temperature creep resistance in relation to the unique microstructure and printability. In this study, we have investigated the microstructure of Cr-rich SS446 ferritic stainless steel produced by L-PBF by microscopical and crystallographic techniques. The properties were compared to the conventionally produced tubes. The rapid cooling and reheating during the application of the subsequent powder layers during L-PBF introduces an intriguing microstructure consisting of a ferritic matrix with precipitation of austenite showing a Kurdjumov–Sachs orientation relationship. Characteristic dislocation networks were observed in the L-PBF samples and contributed to the good mechanical properties in the as-built state (more than twice the yield strength of the conventionally produced tube). Furthermore, the creep resistance at 800 °C was superior to the conventionally produced component, suggesting that L-PBF-produced SS446 possesses many advantages regarding production as compared to the conventional route. [ABSTRACT FROM AUTHOR]

The plasticity of welded 441 ferritic stainless steel joints was controlled by varying the laser beam spot diameter during laser welding. A stainless steel plate thickness of 1.2 mm was used. The microstructures of the welded joints were analyzed for various spot diameters. The elongation of breaks and the reduced area of tensile specimens were analyzed to study the effects of spot diameter on plasticity of the welded joints. The results showed that the weld melt width and weld column crystal size increased with the spot diameter, but isometric crystals in the center of the weld were gradually reduced. Increasing spot diameter resulted in decreased tensile strength, elongation after breaks, and area reduction. So the parameter must be controlled during the laser welding.

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.

Systematic study on the microstructural evolution and mechanical properties of ferritic stainless steel (FSS) 430 with different annealing processes was carried out in the present work. The results show that microstructural refinement can be achieved by optimization of annealing processes, improving elongation, yield strength, and tensile strength of FSS 430. An optimal annealing temperature of 950 ℃ is found with better homogeneity and enhanced mechanical properties among the cold-rolled and annealed FSSs. During annealing processes, the fraction of high-angle grain boundaries of FSS 430 annealed at 950 ℃ is found to be the highest, indicating that a homogeneous microstructure with high recrystallization rate is formed inside the FSS 430 strips. In addition, high fraction of the hard grains (SF < 0.4) and low fraction of the soft grains are found inside FSS 430 annealed at 950 ℃, improving the plasticity of material. Overall, the optimization of annealing processes benefits the microstructural refinement of FSS and thereby improving the mechanical properties of materials. [ABSTRACT FROM AUTHOR]

X2CrNi12 ferritic stainless steel has a wide range of application prospects in the railway transportation, construction, and automobile fields due to its excellent properties. The properties of X2CrNi12 ferritic stainless steel can be further improved by cold-rolling and subsequent annealing treatment. The purpose of this work is to investigate the effect of cold-rolling reduction on the microstructure, texture and corrosion properties of the recrystallized X2CrNi12 ferritic stainless steel by using SEM, TEM, EBSD and electrochemical testing technology. The results show that the crystal orientation characteristics of the cold-rolled sheet could be inherited into the annealed sheet. The higher cold-rolling reduction could promote the deformed grains rotating into the {111} orientation, increasing storage energy and driving force for recrystallization, which could reduce the recrystallized grain size. The orientation densities of α-fiber and γ-fiber were low at 50% cold-rolling reduction. After recrystallization annealing, a large number of grains with random orientation could be produced, and the texture strength was weakened. When the cold-rolling reduction rose to 90%, the γ-fiber texture at {111}<110> was strengthened and the α-fibers, particularly the {112}<110> component, were weakened after recrystallisation annealing, which could improve the formability of the steels. The proportions of special boundaries, i.e., low-angle grain boundaries and low-Σ CSL boundaries, among the grain boundary distribution of the recrystallized X2CrNi12 stainless steel were higher when the reduction was 90%, especially when the annealing temperature was 770 °C. Additionally, the proportion of LAGBs and low-Σ CSL boundaries were 53% and 7.43%, respectively, which improves the corrosion resistance of the matrix, showing the best corrosion resistance. [ABSTRACT FROM AUTHOR]

Magnetically impelled arc butt (MIAB) welding is being used in industries for joining metallic tubes and pipes. This research work reported MIAB welding of AISI 409 ferritic stainless steel tubes of 4 mm thickness. Joints were obtained by varying arc rotation current and characterized using various microscopic techniques. An increase in arc rotation current enlarged the joint region and increased the axial shortening. The upsetting was improper at higher and lower limits of the current. The joint consisted of deformed structure which was thermally and mechanically affected (TMAZ). The entire TMAZ was further designated into three regions based on the variation in grain size and the degree of deformation experienced. The grains were extremely refined by upsetting. There was no coarsening of grains to form a heated affected zone (HAZ). There was no phase transformation observed in TMAZ. The average grain size showed an increasing trend as the current value was increased. High density of dislocations was observed in TMAZ which caused significant strengthening of the joint region. TMAZ showed multifold increase in hardness due to grain refinement and dislocation fields. The variation in arc rotation current influenced the joint strength remarkably and shifted the fracture location. The choice of arc rotation current is a key factor to obtain sound joints. [ABSTRACT FROM AUTHOR]

AISI 430 ferritic stainless steel with different initial microstructures was low-temperature plasma nitrided to improve its hardness and wear resistance in the present investigation. The microstructure and properties of the low-temperature nitrided layers on stainless steel with different initial microstructures were studied by an optical microscope, X-ray diffractometer, scanning electron microscope, microhardness tester, pin-on-disk tribometer, and electrochemical workstation. The results show that the low-temperature nitrided layer characteristics of ferritic stainless steel are highly initial-microstructure dependent. For the ferritic stainless steel with a solid solution and annealing treatment, it had the best performance after low-temperature plasma nitriding when compared with the stainless steel with other initial microstructures. The nitrided layer thickness reached 34 μm after nitriding at 450 °C for 8 h. The phase composition of the low-temperature-nitrided layer consisted mainly of a nitrogen "expanded" α phase (αN) and iron nitrides (Fe4N and Fe2–3N). The hardness of the nitrided layer could reach up to 1832 HV0.1. Moreover, the wear and corrosion resistance of the nitrided layer on the solution and annealing treated ferritic stainless steel could be improved at the same time. [ABSTRACT FROM AUTHOR]

One of the candidates for metallic interconnects of solid oxide fuel cells is ferritic stainless steel, Crofer 22 APU. Ferritic stainless steel Crofer 22 APU specimens with different surface roughness were prepared by grinding with SiC powder papers of various grits and then thermally cycled in air. Variation in the microstructure of the samples having different roughness with thermal cycling was investigated. Polished Crofer 22 APU specimens after three and five thermal cycles had relatively flat oxide layers with thicknesses of about 13.8 and 17.9 µm, respectively. Micrographs of a trench made by milling with FIB (focused ion beam) for a Crofer 22 APU specimen ground with grit 80 SiC powder paper after 8 thermal cycles (total oxygen exposure time of 200 h at 1073 K), captured by ESB (energy selective back-scattering) and SE2 (type II secondary electrons), showed that the surface of the sample was very coarse and its oxide layer was undulated. In the oxide layer, the phase of the sublayer was Cr2O3, and that of the top layer was (Cr, Mn)3O4 spinel. The surface of the sample ground with grit 80 SiC powder paper was very rough after 60 thermal cycles (total oxygen exposure time of 1500 h at 1073 K). The polished Crofer 22 APU is a better applicant to an interconnect of SOFC than those with rougher surfaces. [ABSTRACT FROM AUTHOR]

The influences of ultrasonic vibration during cold metal transfer welding process on the microstructure, element distribution and pitting resistance of AISI 430 ferritic stainless steel joints with ER 308L as filler metal were investigated. The combined effects of mechanical vibration, acoustic streaming and cavitation of ultrasonic vibration significantly refined the primary ferrite grain in the weld metal and then impacted the subsequent solid-phase transition process, leading to the ~45% reduction of ferrite content in the weld metal. Moreover, these effects also resulted in the homogenization of alloying elements in the weld metal. The pitting corrosion resistance of the welded joints with ultrasonic vibration was increased compared with that of without ultrasonic vibration, but lower than the base metal. The pitting resistance of the weld metal with ultrasonic vibration was higher than that of the weld metal without ultrasonic vibration and base metal, while that of the one without ultrasonic vibration was lower than the base metal. [ABSTRACT FROM AUTHOR]

Magnetically impelled arc butt (MIAB) welding is the modern version of the ancient forge welding. The abutting edges are preheated by a rotating arc and upset subsequently. This research work is focused on joining 4-mm thick AISI 409 ferritic stainless steel (FSS) tubes using MIAB welding. Three process parameters namely arc rotation current, upset current, and arc rotation time were varied during welding at five levels according to the chosen central composite design (CCD) of experiments. An empirical relationship was developed to predict the effect of process parameters on the joint strength. The macrostructure and microstructure observations were used to comprehend the predicted plots. Weld zone was composed of fine-grained and deformed structure due to the application of heat and pressure and called as thermo mechanically affected zone (TMAZ). Factors such as poorly forged structure, voids, and oxide particles influenced the joint strength adversely. In spite of significant strengthening of the TMAZ, a clearly forged interface was essential to obtain higher joint strength. [ABSTRACT FROM AUTHOR]

The advantage of ferritic stainless steels (FSS’s) over austenitic stainless steels is that they are less expensive alloys. This is due to low or negligible nickel in its alloying element which makes the steel affordable. This type of steel is highly recommended against chloride attack and is also machinable to produce various components for engineering applications. This study examines the effect of various fillers on 430 ferritic stainless steel (FSS). The austenitic (308) and ferritic (410) grades of filler were used to study the weldability, microstructure, mechanical properties, and corrosion resistance using tungsten inert gas welding. The findings showed the emergence of various complex phases in both the weld sample. The sample welded with 410 filler shows acicular ferrite, martensite and austenite. Whereas, austenite and vermicular ferrite are observed in the sample welded with 308 filler. Based on compositions and solidification modes, the mechanical properties of welded joints also vary. It was found that ferritic mode solidified welds dominated in terms of qualities, which was found in 410 filler. In the chloride solution, the behaviour of the pitting corrosion resistance of each weld varied. The sample welded with 410 was superior corrosion resistance. This is due to more δ -ferrite in the weld sample. Whereas, 308 showed poorer resistance against the simulated seawater solution. In 410 welds, a greater degree of sensitization was observed, as compared to 308 welds.

Despite extensive research and proposed theories on formation and breakdown of passive layers, several questions remain unanswered. These include the reasons behind the bi-layer nature of the passive layer, the decrease in hydrogen and oxygen diffusivity upon entering the passive layer, and the influence of microstructure on passive layer formation and function in stainless steels. In this study, we employed ReaxFF molecular dynamics simulations to investigate passivation and depassivation of ferritic stainless steels in a polycrystalline structure. Through static and dynamic calculations, we elucidated the underlying mechanisms of passive layer formation, which were primarily governed by clustering. Our analysis also highlighted the significant role of hydrogen diffusion and its reaction with metallic compounds in the depassivation process. We have identified several physical phenomena involved in the processes of passivation and depassivation, which can provide explanations for the questions posed above. [Display omitted] • Clustering and local detachment of metallic atoms are the main drivers behind the formation of passive layers in ferritic stainless steels. • Microstructure, including point defects and extended defects play a critical role in the formation and degradation of passive layers. • Hydrogen plays a crucial role in the diffusion of solution constituents and passive layer breakdown. • Not only the bi-layer character of the passive layer but also its composition gradient can be explained. [ABSTRACT FROM AUTHOR]

Friction stir welding(FSW) was performed for 4mm thick T4003 ferritic stainless steel(FSS) with different welding parameters. The effect of welding parameters on microstructure, hardness distribution, and impact toughness of FS-welded joints at room temperature and low temperature was investigated. The results show that the stir zone(SZ) and the thermo-mechanically affected zone (TMAZ) consist of duplex structure of ferrite and martensite. The SZ is heterogeneous along the thickness of the joint and this trend gets more obvious with the decrease of rotational speed and increase of welding speed. In the heat affected zone(HAZ) of the advancing side, the microstructure transits smoothly and no obvious characteristics of deformation and elongation as the rotational speed increases to 250r/min from 150r/min. The hardness distribution of the weld is relatively uniform and the maximum hardness is 290HV, approximately 1.87 times than that of the base material(BM). The welding parameters and temperature exert great effect on the impact absorbing energy of the welded joint. The impact absorbing energy of HAZ and SZ are up to 90%-92%, and 85%-103% of BM, respectively, at room temperature(20℃). While at low temperature(-20℃), the impact absorbing energy of HAZ and SZ reaches 87%-97%, and 82%-95% of BM, respectively. It shows that the weld zone still has better matching between strength and toughness.

This experimental study examines the effects of dissimilar welding of 316L austenitic and 430 ferritic stainless steels, welded with gas tungsten arc welding process with (ER316L and ER309L) and without fillers (autogenous). Microstructural examination was performed by optical and scanning electron microscopy. ER316L and ER309L fillers welds illustrated equiaxed and columnar grains; ER309L weld showed higher Creq/Nieq ratio than that of ER316L weld, produced vermicular ferrite, while autogenous weld shows lathy ferrite and martensite. Chromium carbide precipitate was also observed in autogenous weld. The mechanical properties were measured and higher hardness was obtained in autogenous weld compared to ER316L and ER309L filler weld. Higher tensile and impact strength was measured in ER316L filler weld as compared to ER309L filler and autogenous weld. The corrosion resistance of the joints was carried out by double loop electrochemical potentiokinetic reactivation and potentiodynamic polarization test to assess the sensitization and pitting resistance, respectively. Higher degree of sensitization and pitting were observed in autogenous weld as compared to ER316L and ER309L filler weld due to precipitation formation, but the pitting corrosion was found to be lower for ER309L filler weld as compared to ER316L filler and autogenous weld due to the effect of mode of solidification. [ABSTRACT FROM AUTHOR]

Copyright of Light Industry Machinery is the property of Light Industry Machinery 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.)

In this work, the effect of Cu addition on the microstructure and corrosion passivation behavior of Sn alloyed ferritic stainless steel in 3.5 wt.% NaCl solution at 30 °C was investigated by optical microscope (OM), scanning electron microscope (SEM), energy-dispersion spectrum (EDS), potentiodynamic polarization curve and x-ray photoelectron spectroscopy (XPS). The results indicate that Cu addition has certain effect on grain refinement of ferritic stainless steel. Meanwhile, Cu addition has little influence on the cathodic corrosion process of ferritic stainless steel in 3.5 wt.% NaCl solution but shows beneficial effect on enhancing both the corrosion resistance of steel substrate and its passivation behavior. It has been found that the deposition of Cu particles at the bottom of corrosion pits is responsible for the better corrosion resistance and passivation behavior of ferritic stainless steel. Moreover, there is synergistic effect between Sn and Cu on enhancing the corrosion resistance of ferric stainless steel matrix and improving its passivation behavior in NaCl solution. [ABSTRACT FROM AUTHOR]

Ferritic stainless steel (FSS 430) has been deformed by equal-channel angular pressing (ECAP) at room temperature at an equivalent strain (εvm) of 1.2 by adopting the route Bc. Microstructural developments were studied by optical microscopy, transmission electron microscopy, and microtexture by electron backscattered diffraction. Typical ultrafine-grains of less 0.2 µm could be identified. The XRD patterns confirm the presence of a BCC phase alone. An increase in peak broadening is attributed to the reduction of crystallite size and increase of lattice strain arising from deformation during ECAP. The grain refinement takes place through simple shear deformation by elongation of grains, splitting of grains into bands, the subdivision of bands into subgrains by dynamic recovery, and conversion of subgrains into grains by progressive lattice rotation (PLR). Weakly textured rolled ferritic stainless steel is strongly textured at an imposed equivalent strain of 0.6 with the development of ideal shear components of D2θ and E ¯ θ for bcc materials. On the second pass of ECAP texture is partially randomized and the intensity of components was decreased and new components of D1θ and Fθ are developed due to subdivision of grains into bands, bands into subgrains, and conversion of subgrains into grains of high angle of misorientation by PLR. The yield strength, tensile strength, and hardness are increased almost 1.5 times that of as-received coarse-grained material due to a high degree of grain refinement and an increase in defect density or strain. The yield strength of 687 MPa of as-received material was enhanced to 1093 MPa of ECAPed ferritic stainless steel. However, the material has lost its ductility significantly due to high defect density and a significant amount of non-equilibrium nature of grain boundaries. [ABSTRACT FROM AUTHOR]

• SLM-fabricated 430 FSS exhibits significant anisotropy. • SLM-fabricated 430 FSS contains second-phase oxides and high dislocations. • SLM-fabricated 430 FSS exhibits excellent strength with limited plasticity. • SLM-fabricated 430 FSS shows cleavage fractures. This study investigates the microstructure and mechanical properties of 430 ferritic stainless steel (FSS) fabricated via the selective laser melting (SLM) process. The mechanical properties and fracture morphologies of SLM-fabricated 430 FSS and conventional 430 FSS were compared in this paper. It was found that 430 FSS produced by SLM exhibits significant microstructural anisotropy, with higher dislocation density and the presence of oxides of silicon, manganese and aluminum. Regarding mechanical properties, 430 FSS fabricated via SLM process displays higher tensile strength and yield strength, as well as superior product of strength and elongation (PSE) and yield ratio, compared to those produced by conventional methods. Fracture morphology analysis revealed that SLM-fabricated 430 FSS primarily exhibited characteristics of cleavage fractures, whereas conventional 430 FSS showed typical features of ductile fractures. [ABSTRACT FROM AUTHOR]

The influences of ultrasonic vibration during cold metal transfer welding process on the microstructure, element distribution and pitting resistance of AISI 430 ferritic stainless steel joints with ER 308L as filler metal were investigated. The combined effects of mechanical vibration, acoustic streaming and cavitation of ultrasonic vibration significantly refined the primary ferrite grain in the weld metal and then impacted the subsequent solid-phase transition process, leading to the ~45% reduction of ferrite content in the weld metal. Moreover, these effects also resulted in the homogenization of alloying elements in the weld metal. The pitting corrosion resistance of the welded joints with ultrasonic vibration was increased compared with that of without ultrasonic vibration, but lower than the base metal. The pitting resistance of the weld metal with ultrasonic vibration was higher than that of the weld metal without ultrasonic vibration and base metal, while that of the one without ultrasonic vibration was lower than the base metal.

This work investigates the effect of friction stir welding process parameters (rotation rate and traverse speed) on the microstructural evolution of friction stir welded (FSWed) ferritic stainless steel (FSS) AISI 409. Optical microscope, scanning electron microscope and electron backscattering diffraction are used to quantitatively assess the development in grain structure and texture. The microstructural development suggested that thermo-mechanical deformation occurs in the stir zone within the austenite/ferrite phase region, ultimately transforming upon cooling into bainitic/ferritic microstructure. The fraction and size of the bainitic/ferritic grains are found to vary through the thickness of the joints. High fractions of coarse ferritic grains are found near the top of the stir zone, and low fraction of fine ferritic grains is found near the bottom of the stir zone. This bainitic/ferritic grain structure resulted in an increase in the hardness of the stir zone by about 74% relative to the base material. The tensile strength of the FSWed FSS joints is almost at the same level of the base material with reduction in the ductility as a result of the increased hardness of the weld zone. [ABSTRACT FROM AUTHOR]

In order to study the effect of cold rolling process on the formability of 19Cr2Mo1 W ferritic stainless steel, the micro structure and texture evolution of this steel during cold-rolling and annealing processes were investigated by X-ray diffraction (XRD), electron back-scatter diffraction (EBSD), roughness and plastic strain ratio analytical methods. The results indicated that the amount of α and γ fiber textures in cold-rolled sheet increased with the increase of cold rolling reduction, and the stable orientation of α and γ fiber textures during cold rolling was {223} 〈110〉 and {111} 〈011〉 component, respectively. In addition, the strength of the γ recrystallization texture became higher, when the amount of {223} 〈110〉 component increased. After annealing at1 050 °C for 1 min, the recrystallized ferritic grains in the sheet distributed uniformly with a fine grain size, the surface roughness was small and the strength of the γ fiber texture was relatively high, i. e., the formability of the cold-rolled steel sheet was the best. [ABSTRACT FROM AUTHOR]

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Highlights • Q&P processes were applied to both the hot rolled and cold rolled AISI 430 stainless steels. • The Q&P microstructure consisted of ferrite, twin martensite and retained austenite. • High tensile strength together with large elongation were acquired after Q&P processes. Abstract High tensile strength and large elongation are obtained by applying the Q&P process to the hot rolled or directly cold rolled AISI 430 ferritic stainless steels characterized by ferrite, twin martensite and retained austenite. Both the prior formed martensite during the quenching and the TRIP effect of the retained austenite account for the improved tensile strength and the retained austenite gives a promotion to the large elongation. [ABSTRACT FROM AUTHOR]

This paper investigated the microstructure and mechanical properties of AISI 430 ferritic stainless steel (FSS) after annealing in either the single-phase or two-phase region, followed by different cooling manners: water cooling, air cooling and furnace cooling. After annealing at 840 °C in the single-phase region, the sample consisted primarily of ferrite, with M 23 C 6 and M 2 (C, N) precipitates aligned mainly along the rolling direction (RD). For the water-cooled and air-cooled samples annealed at 950 °C in the double-phase region, they formed a dual-phase structure comprising ferrite and martensite, with precipitations primarily located within the martensite lath. Conversely, the sample subjected to annealing at 950 °C followed by furnace cooling displayed a single ferrite structure, owing to the decomposition of austenite. In this case, the precipitations were mainly found along the grain boundaries, with some also forming within the ferrite grain. The paper delved into the analysis of mechanical properties and strengthening mechanism through tensile experiments and fracture morphology examination. The influence of heating range and cooling manner on the yield characteristics of FSS was discussed. The results indicated that the air-cooled and furnace-cooled samples annealed at 840 °C displayed a clear yield platform in their tensile curves. Conversely, the samples treated with other heat treatments exhibited continuous yielding or no obvious yield platform. This difference may be attributed to the influence of heating temperature range and cooling manner on the distribution of dislocations and interstitial atoms within the ferrite grains. [ABSTRACT FROM AUTHOR]

In the present investigation, thin sheets of stabilized and unstabilized ferritic stainless steel were welded in butt joint configuration using irradiation of a 1070 nm fiber-laser. Using optical microscopy, the microstructural evolution upon alternating heat input was characterized. In addition to that, hardness and tensile tests were carried out on the specimens. Detailed focus was given to the intergranular corrosion properties, which were investigated on basis of the Strauss test with different times of exposure to the corrosive environment. Following these tests, the mechanical properties of the joints were characterized using tensile tests. A combination of the latter with an inspection by μ-CT analysis allows for the proposition of an intergranular corrosion rate with regard to the degradation of the joint strength.

The influence of grinding operations on surface properties and corrosion behavior of a ferritic stainless steel (FSS), EN 1.4509, has been investigated and limited comparisons also made to the grade EN 1.4622. Surface grinding was performed along the rolling direction of the material. Corrosion tests were conducted in boiling magnesium chloride solution according to ASTM G36; specimens were exposed both without external loading and under four‐point bend loading. The surface topography and cross‐section microstructure before and after exposure were investigated, and residual stresses were measured on selected specimens before and after corrosion tests using X‐ray diffraction. In addition, in situ surface stress measurements were performed to evaluate the actual surface stresses of specimens subject to four‐point bend loading according to ASTM G39. Micro‐pits showing branched morphology initiated from the highly deformed ground surface layer which contained fragmented grains, were observed for all the ground specimens but not those in the as‐delivered condition. Grain boundaries under the surface layer appeared to hinder the corrosion process. No macro‐cracking was found on any specimen after exposure even at high calculated applied loads. The influence of grinding operations on surface properties and corrosion behavior of a ferritic stainless steel, EN 1.4509, has been investigated and limited comparisons also made to the grade EN 1.4622. Grain boundaries under the surface layer appeared to hinder the corrosion process. No macro‐cracking was found on any specimen after exposure even at high calculated applied loads. [ABSTRACT FROM AUTHOR]

The solidification structure of ferritic stainless steel can be refined by controlling the contents of Ti, O, and N in the liquid steel through the thermodynamic analysis and high-temperature experiment. It is found by the scanning electron microscopy technology, in which the composite core of Ti nitride-enwrapping Ti oxide can be formed in the solidification front, which promotes the nucleation of δ iron and refines the solidification structure. Meanwhile, the structure analysis of the composite core by the transmission electron microscope technology proves that the Ti oxide that exists in the centre of the composite core is Ti2O3 and the Ti nitride that exists in the outer layer of the composite core is TiN. [ABSTRACT FROM AUTHOR]

The evolution of microstructure and texture of Fe-19Cr-2Mo-Nb-Ti ferritic stainless steel annealed at different temperatures was investigated using a combination of X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). EBSD investigations confirm that the in-grain shear bands provide more recrystallization nucleation sites to γ-fiber recrystallization grains with high Taylor factor orientations during cold rolling requiring further annealing for a more homogenous equiaxied grain structure. As the annealing temperatures increase, the grains in center layer are oriented towards {110}∥ND, and the recrystallization grains at 1050 °C are dominated by the uniform and equiaxial γ-fiber grains favourable for the improvement of r-values, while the occurrence of {100} 〈011〉 texture detrimental to r-values indicates that an exorbitant annealing temperature can reduce the intensity of γ-fiber textures affecting the formability, accordingly, the average plastic strain ratio of ferritic stainless steel increases sharply up to a maximum value (1.69) and then decreases to a certain value (1.42). [ABSTRACT FROM AUTHOR]

We investigated the effect of Sn micro-alloying on recrystallization nucleation and growth processes of ferritic stainless steels. The as-received hot rolled sheets were cold rolled up to 80% reduction and then annealed at 740-880 °C for 5 min. The cold rolling and recrystallization microstructures and micro-textures of Sn-containing and Sn-free ferritic stainless steels were all determined by electron backscatter diffraction. Our Results show that Sn micro-alloying has important effects on recrystallization nucleation and growth processes of ferritic stainless steels. Sn micro-alloying conduces to grain fragmentation in the deformation band, more fragmented grains are existed in Sn-containing cold rolled sheets, which provides more sites for recrystallization nucleation. Sn micro-alloying also promotes recrystallization process and inhibits the growth of recrystallized grains. The recrystallization nucleation and growth mechanism of Sn-containing and Sn-free ferritic stainless steels are both characterized by orientation nucleation and selective growth, but Sn micro-alloying promotes the formation of γ-oriented grains. Furthermore, Sn micro-alloying contributes to the formation of Σ13b CSL boundaries and homogeneous γ-fiber texture. Combining the results of microstructure and micro-texture, the formability of Sn-containing ferritic stainless steels will be improved to some extent. [ABSTRACT FROM AUTHOR]