Ferrite Content Research Articles

Effect of Filler Wire Composition on Weld Metal Microstructure and Mechanical Properties in X80 Steel Laser Welds

Laser welding was performed using different filler wires, ER70S steel, commercially pure iron, and pure nickel filler, in the context of welding X80 pipeline steel to assess the microstructure and mechanical properties of the weld metal. Introducing an ER70S wire promoted acicular ferrite formation in the fusion zone, compared to a bainitic microstructure in an autogenous laser weld. The use of pure iron wire was considered as a potential strategy for reducing hardenability, as it led to the dilution of alloying elements in the fusion zone, increasing ferrite content and reducing weld metal hardness to a level compliant with API pipeline standards. The addition of pure nickel wire was used to reveal the degree of weld metal mixing imposed by the laser (thus providing an unambiguous tracer element) when it is combined with filler material dilution in the fusion zone, revealing that the upper region contained 38% wire material and the lower region only 12%. This accounts for the differences observed between the upper versus lower portions of the weld metal when other wires are used, and the use of hardness mapping and micro-indentation demonstrates the correlation between the variations in mechanical properties and microstructural differences introduced by incomplete mixing of the filler wire elements.

A Review of Welding Process for UNS S32750 Super Duplex Stainless Steel

Super duplex stainless steel UNS S32750 is widely used in marine industries, pulp and paper industries, and the offshore oil and gas industry. Welding manufacturing is one of the main manufacturing processes to make material into products in the above fields. It is of great importance to obtain high-quality welded UNS S32750 joints. The austenite content and ferrite content in UNS S32750 play an important role in determining UNS S32750 properties such as mechanical properties and corrosion resistance. However, the phase proportion between the ferrite phase and austenite phase in the welded joint will be changed during welding. Lots of research has been done on how to weld UNS S32750 and how to obtain welded joints with good quality. In this work, the recent studies on welding UNS S32750 are categorized based on the welding process. The welding process for UNS S32750 will be classified as gas tungsten arc welding, submerged arc welding, plasma arc welding, laser beam welding, electron beam welding, friction stir welding, and laser-MIG hybrid welding, and each will be reviewed in turn. The microstructure and properties of the joints welded using different welding processes will also be discussed. The critical challenge of balancing the two phases of austenite and ferrite in UNS S32750 welded joints will be discussed. This review about the welding process for UNS S32750 will provide people in the welding field with some advice on welding UNS S32750 super duplex stainless steel.

Development of Scaffolds with Chitosan Magnetically Activated with Cobalt Nanoferrite: A Study on Physical-Chemical, Mechanical, Cytotoxic and Antimicrobial Behavior.

Background/Objectives: This study investigates the development of 3D chitosan-x-cobalt ferrite scaffolds (x = 5, 7.5, and 10 wt%) with interconnected porosity for potential biomedical applications. The objective was to evaluate the effects of magnetic particle incorporation on the scaffolds' structural, mechanical, magnetic, and biological properties, specifically focusing on their biocompatibility and antimicrobial performance. Methods: Scaffolds were synthesized using freeze-drying, while cobalt ferrite nanoparticles were produced via a pilot-scale combustion reaction. The scaffolds were characterized for their physical and chemical properties, including porosity, swelling, and mechanical strength. Hydrophilicity was assessed through contact angle measurements. Antimicrobial efficacy was evaluated using time kill kinetics and agar diffusion assays, and biocompatibility was confirmed through cytotoxicity tests. Results: The incorporation of cobalt ferrite increased magnetic responsiveness, altered porosity profiles, and influenced swelling, biodegradation, and compressive strength, with a maximum value of 87 kPa at 7.5 wt% ferrite content. The scaffolds maintained non-toxicity and demonstrated bactericidal activity. The optimal concentration for achieving a balance between structural integrity and biological performance was found at 7.5 wt% cobalt ferrite. Conclusions: These findings suggest that magnetic chitosan-cobalt ferrite scaffolds possess significant potential for use in biomedical applications, including tissue regeneration and advanced healing therapies. The incorporation of magnetic properties enhances both the structural and biological functionalities, presenting promising opportunities for innovative therapeutic approaches in reconstructive procedures.

Research on corrosion performance of Q235B steel in industrial coastal atmospheric environment

This study aims to obtain the effect of SO2 on the corrosion of Q235B low carbon steel in simulated coastal industrial atmospheres.The corrosion performance of the steel in the simulated atmospheres was studied using wet/dry cyclic corrosion test (CCT), electrochemical testing analysis, scanning electron microscopy, X-ray diffraction, and COMSOL finite element simulation methods. As a result the influence of SO2, the corrosion rate of Q235B steel increases rapidly in the initial stage of corrosion, and gradually decreases in the later stages, eventually stabilizing. There is a gradual increase in ferrite content on the surface of the steel during the initial stage of corrosion. In addition, the main components of the rust layer α-FeOOH and γ-FeOOH, and high concentrations of SO2 promote α-FeOOH formation and inhibit γ-FeOOH formation.

Effects of heat input on microstructure evolution and corrosion resistance of underwater laser cladding high-strength low-alloy steel coating

The effects of heat input on the microstructure evolution and corrosion resistance of the high-strength low-alloy (HSLA) steel coating obtained by wire-feed underwater laser cladding were studied. Optical digital microscope, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscope (TEM), electron back-scattered diffraction (EBSD), electrochemical tests, laser microscope and other characterization methods were used. As the heat input increased, the smoothness of the underwater cladding coating improved, with little changes in elemental distribution and phase composition. However, the content of acicular ferrite increased, while the amounts of lath bainite, lath martensite, and granular bainite decreased. As the heat input increased from 0.4 to 0.55 kJ/mm, the grain size increased from 25.3 to 55.9 μm, the proportion of low-angle grain boundaries rose from 61.3 % to 69.1 %, and the texture intensity of the (110) crystal plane increased from 16.22 to 23.83. Meanwhile, the dislocation density decreased from 4.9 × 1014 to 4.1 × 1014 m−2. These changes enhanced the corrosion resistance of underwater coating. As the heat input increased from 0.4 to 0.55 kJ/mm, the corrosion current density decreased from 2.13 × 10−5 to 3.35 × 10−6 A/cm2, and the corrosion potential increased from −0.823 to −0.529 V. Additionally, the depth-to-width ratio of the corrosion pits decreased from 0.255 to 0.053. This study laid the foundation for high-quality in-situ underwater repairs of ships and submarines made of high-strength steel.

Optimization of Mn-Zn ferrite doping in phosphate-based glass ceramics for enhanced hyperthermia efficiency and bioactivity

This study investigates the effects of Mn-Zn ferrite (MZF) content and heat treatment temperature on the structural, mechanical, magnetic, and bioactive properties of Na2O-CaO-P2O5 glass ceramics. Various MZF contents (5MZF, 10MZF, 20MZF, and 40MZF) were incorporated into the glass ceramics and subjected to heat treatment at different temperatures (600, 650, 700, and 800 °C). The results demonstrated that increasing the MZF content significantly enhanced the mechanical properties, including Vickers hardness, Knoop hardness, and Young's modulus. For example, the Vickers hardness values increased from 5.6 GPa in 5MZF samples to 7.1 GPa in 40MZF samples. X-ray diffraction analysis revealed the presence of major crystalline phases, such as Ca2P2O7 and Na4Ca(PO3)6, with NaFe3P3O12 and (Zn,Mn)Fe2O4 appearing in samples with higher MZF content. Magnetic measurements indicated that the 40MZF samples treated at 700 °C reached a satisfactory hyperthermia temperature of 43 °C within 16 min. Bioactivity tests showed a decrease in bioactivity with increasing MZF content, whereas cytotoxicity assays confirmed that all MZF-Na2O-CaO-P2O5 bioactive glass ceramics were non-toxic, maintaining over 100 % cell viability after 24 h. These findings suggest that MZF-containing glass ceramics have potential applications in the biomedical field, particularly when enhanced mechanical and magnetic properties are required.

Crystal Structure, Optical, Photoluminescence, Raman, and Magnetic properties for Sm-doped Cr-Mg-Bi Ferrites using sensor

The current work,A series of rare earth Sm3+ ion substituted Cr-Mg-Bi ferrites Cr0.7Mg0.2Bi0.1SmxFe2-xO4 (x = 0.00, 0.02, 0.04, and 0.06) have beensynthesized by thesol-gel auto-combustion method. The XRD, FESEM, HRTEM,UV-Vis, FTIR, Raman spectroscopy, Photo Luminesce and Magnetic Properties analysis have been used to investigate structural, morphological, optical, Raman spectroscopy, Photo Luminesce and Magnetic Properties. Every sample contains a single-phase spinel structure, as confirmed by XRD.The substitution of Sm3+ ions is found to increase the lattice parameter from 8.258–8.248Å.A monotone diffraction peak (311) is visible near small angles of degrees (35.33 to 35.13). The Debye-Scherrer equation, the nanoparticles' crystallite size ranges from 35.357–54.778 nm.FE-SEMs reveal a spherical grain that groups and has a porous form, with particles 38.13 to 53.28 nmin size.HR-TEM micrographs illustrate spherical morphology and their average particle size decreases from 55.32 to 65.42 nm. The selected area electron diffraction (SAED) pattern confirms the crystal planes which were revealed from XRD calculations.The spinel structure was confirmed by FTIR spectroscopy, which found 414 cm-1 and 516 cm-1 vibrational band at the octahedral and tetrahedral sites.As the concentration of Sm3+ rises, the direct and indirect band gap energy values determined from UV-Vis show an increase and decrease.The generated NPs' semiconducting nature is confirmed by the strong correlation between the g-value and particle size change.Photoluminescence (PL) investigation shows that all processed samples have four bands.(i) peak centered at 412 nm, which is near-band edge emission and corresponds to the ultraviolet (UV) band,(ii) The violet band has a high-intensity peak at 434 nm,(iii) The blue band is related to a low-intensity, sharp peak located at 466 nm, and (iv) A broad peak at 502 nm with a very low intensity distinguishes the green band.The Raman spectroscopy investigation revealed that the CMBSF nanoparticles had a mixed spinel structure. The magnetic investigation shows that when the Sm content of ferrites increases, saturation magnetization drops from 39.86 to 33.16 emu/g.The sample's coercivity (Hc) increases from 16.06 to 21.90 KOe with Sm substitution.

Feasibility of manufacturing high-aspect-ratio hollow tubes of SS410 through wire-arc directed energy deposition

This study reports new observations from the fabrication of high-aspect-ratio hollow tubes of SS410 through wire-arc directed energy deposition (wire-arc DED) process. Characterisation work was performed on a single tube as a function of its build height. The maximum ultimate tensile strength (UTS) of 1372 MPa and maximum yield strength (YS) of 980 MPa were achieved in the middle region of the tube. The highest UTS in the middle was attributed to the low delta ferrite content. The reduction of delta ferrite was found to be linked with the repetitive heating and cooling. In contrast, the top and bottom sections exhibit a substantial presence of delta ferrite, indicating that the cyclic effects were not considerable. Nevertheless, the presence of significant ductility in the bottom region of the component indicated the occurrence of tempering effects. This observation is further supported by the lower levels of local strain observed using KAM mapping. Overall, this work proposes a novel fabrication method for producing hollow sections with superior strength and ductile properties.

Performance analysis of various fluxes in different variants of the TIG welding process on the quality of welding

The tungsten inert gas (TIG) welding process is widely used in various industries for its ability to produce high-quality welds at a low cost. However, TIG welding struggles with welding thick stainless steel in a single pass, reducing production efficiency. To address this, new TIG variants such as activated TIG (A-TIG), flux bound TIG (FB-TIG), and flux zone TIG (FZ-TIG) have been developed to enhance penetration in austenitic stainless steel. This study investigates the effects of TiO2 and Fe2O3 flux on 304 stainless steels welded using A-TIG, FB-TIG, and FZ-TIG processes. Results show a slight increase in the depth-to-width (d/w) ratio for A-TIG and FB-TIG, while FZ-TIG achieved a 59% higher d/w ratio compared to autogenous TIG welding. The increased penetration is attributed to the reversal Marangoni convection and arc constriction. Microstructural analysis reveals a higher delta ferrite content in A-TIG and FZ-TIG welds due to increased heat input. Additionally, FZ-TIG welds exhibited an 11.5% higher microhardness compared to autogenous TIG welds. FZ-TIG welding enhances penetration and mechanical properties effectively.

Study on the Effect of Pressure on the Microstructure, Mechanical Properties, and Impact Wear Behavior of Mn-Cr-Ni-Mo Alloyed Steel Fabricated by Squeeze Casting

ZG25MnCrNiMo steel samples were prepared by squeeze casting under pressure ranging from 0 to 150 MPa. The effects of pressure on the microstructure, low-temperature toughness, hardness, and impact wear performance of the prepared steels were experimentally investigated. The experimental results indicated that the samples fabricated under pressure exhibited finer grains and a significant ferrite content compared to those produced without pressure. Furthermore, the secondary dendrite arm spacing of the sample produced at 150 MPa decreased by 45.3%, and the ferrite content increased by 39.1% in comparison to the unpressurized sample. The low-temperature impact toughness of the steel at −40 °C initially increased and then decreased as the pressure varied from 0 MPa to 150 MPa. And the toughness achieved an optimal value at a pressure of 30 MPa, which was 65.4% greater than that of gravity casting (0 MPa), while the hardness decreased by only 6.17%. With a further increase in pressure, the impact work decreased linearly while the hardness increased slightly. Impact fracture analysis revealed that the fracture of the steel produced without pressure exhibited a quasi-cleavage morphology. The samples prepared by squeeze casting under 30 MPa still exhibited a large number of fine dimples even at −40 °C, indicative of ductile fracture. In addition, the impact wear performance of the steels displayed a trend of initially decreasing and subsequently increasing across the pressure range of 0–150 MPa. The wear resistance of samples prepared without pressure and at 30 MPa was superior to that at 60 MPa, and the wear resistance deteriorated when the pressure increased to 60 MPa, after which it exhibited an upward trend as the pressure continued to rise. The wear mechanisms of the samples predominantly consisted of impact wear, adhesive wear, and minimal abrasive wear, along with notable occurrences of plastic removal, furrows, and spalling.

4D printing of the ferrite permanent magnet BaFe12O19 and its intelligent shape memory effect

4D printing of the barium ferrite permanent magnets provides new opportunities for intelligent structure and process innovation of permanent magnets. In this paper, the preparation, filament manufacture, and intelligent printing methods with shape memory/recovery effect are studied for the barium ferrite permanent magnet. Firstly, the PLA/TPU/BaFe12O19 composite materials are developed by adding different contents of ferrite permanent magnet BaFe12O19 powders into the PLA/TPU (polylactic acid/thermoplastic polyurethane) matrix. The weight percentage of the BaFe12O19 is 10–40 wt% with an interval of 10 wt%. Secondly, the composites are pelletized and further extruded to manufacture composite filaments with different BaFe12O19 contents. Scanning electron microscope (SEM) is used for the microstructural analysis. The BaFe12O19 particles are uniformly distributed in the PLA/TPU matrix, and the slight particle agglomeration phenomenon occurs in the composite filaments with 30 and 40 wt% BaFe12O19. The thermal properties of PLA/TPU/BaFe12O19 composite filaments are analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). After adding the barium ferrite particles, the glass transition temperature of the composite filaments changes within a small range from 53.5 °C to 55 °C. Thirdly, the filaments are successfully manufactured to magnet parts by the fused deposition modeling (FDM) 3D printing for the tests of mechanical, magnetic, and shape recovery properties. With the increase of the barium ferrite content, the magnetic properties show a rising trend, proving the feasibility of using 3D printing technology to make magnets. The shape memory effects of the printed parts are excellent and the shape recovery ratios show a rising trend, from 85.6 % to 88.9 % under heat contact stimulus and from 88.9 % to 97.8 % under electromagnetic induction non-contact stimulus. Relatively, the parts hold fast response speed due to direct contact with the heat source under the heat stimulus, and the parts hold higher shape recovery ratios due to more heats produced under the electromagnetic induction stimulus. The addition of magnetic particles is helpful to improve the heat transfer ability and provide the possibility of non-contact heat transfer. The magnetic parts with complex structure and intelligent shape memory/recovery effect can be achieved for special application requirements. As a result, the research of this paper expands preparation methods of new magnetic composite materials, explores the manufacture process for intelligent magnets and lays a solid foundation for the development of new permanent magnet devices.

Effect of microstructural inheritance window on the mechanical properties of an intercritically annealed Q&P steel

Different initial microstructures significantly influence the final microstructures and mechanical properties of the intercritically annealed quenching and partitioning steels. Previous studies have primarily focused on the mechanism for the inheritance of different initial microstructures into the final microstructures, which affects the phase fraction and mechanical properties. However, these studies have overlooked the existence of an inheritance window in the intercritical annealing process. In this study, we investigated the inheritance window and explored the impact of varying initial microstructures on the reverse transformation of austenite, final phase fraction, and mechanical properties. Our findings reveal that the varying initial microstructure exhibits minimal influence on the final microstructure and mechanical properties for short or long annealing times. However, for the intercritical annealing treatment for 60 s, the initial microstructure of martensite with more nucleation sites accelerated the austenite reverse transformation fraction, enhanced the reverse-transformed austenite content, increased the primary martensite content, and improved the yield strength. Conversely, the coil-cooled sample, with initial microstructures consisting of ferrite and pearlite without dissoluble Mn-rich cementites, reduced the austenite reverse transformation rate, decreased the reverse-transformed austenite content, enhanced the ferrite and RA content, and improved ductility.

Experimental review and accuracy of etchants used for phase analysis of SAF2507 Super Duplex Stainless Steel

The mechanical and corrosion properties of duplex stainless steels (DSS) depend on the distribution of ferrite and austenite as well as the presence of secondary phases. It is therefore necessary to accurately determine both the distribution of the phases and their morphology. The aim of this research is to define a standard method for the determination of the volume fraction of the phases present in a SAF2507 SDSS by analysing images acquired by light microscope. To do this, the material is heat-treated at 850 °C for 5 min, 15 min, 30 min, 1h, 5h to stimulate the formation of the σ-phase. The metallographic etchant capable of maximising phase contrast is then identified. Micrographic analyses are performed using different reagents at different holding times and temperatures, in order to find the best combination. A standard procedure is then defined for the image analysis. The data obtained were are processed to calculate the phase distribution. The results are compared with the quantitative analysis performed using X-ray diffraction as reference.The research evidence that Kalling's reagent is best etchant for fully solubilised materials, as it accurately estimates ferrite and austenite content. On the other hand, Marble's reagent should be preferred for the detection of σ-phase. For comprehensive analysis of all phases, Murakami's reagent is recommended.The approach defined in this paper not only improves the understanding of the microstructure of DSS, but also provides an important tool for industrial quality control and material characterisation.

Machine learning-assisted wire arc additive manufacturing and heat input effect on mechanical and corrosion behaviour of 316 L stainless steels

Predicting the track forming factor or height-to-width ratio (H/W) in wire arc additive manufacturing is crucial for optimal path planning, heat distribution, structural integrity, distortion control, process efficiency, and defect prevention, ensuring high-quality and reliable components. Different analytical and numerical modeling methods have been introduced to predict the H/W ratio. However, the accuracy of these predictions is relatively low due to the challenges associated with handling complex and non-linear regression equations. This study addressed the challenges by implementing data-driven predictive modeling to predict the H/W ratio from the input process parameters. A stacking ensemble learning approach is employed, where a meta-model integrates predictions from multiple base learners to enhance overall performance. The model performance was evaluated by Coefficient of determination (R2), mean squared error (MSE), and mean absolute error (MAE). The model was validated by comparing the experimental and predicted values based on which five thin walls are printed with different heat inputs. The study also explores the impact of heat input on microstructure, mechanical, and corrosion properties. The findings indicate that a significantly low heat input (178 J/mm) and higher heat inputs (> 356 J/mm) decrease the wire utilization. With increasing heat input, ferrite content increases, microstructures become coarser, dendritic spacing increases, and ferrite transitions from lathy to skeletal. Further, lower heat input (235 J/mm) reduces δ-ferrite, suppresses atomic segregation, and increases Cr and Mo in the matrix. YS and UTS decrease with higher heat inputs, anisotropy decreases, and Vickers microhardness drops from 228 (178 J/mm) to 194 Hv (586 J/mm). Additionally, the corrosion resistance deteriorates with increasing heat input, as evidenced by higher pitting potential (Epit: 0.389 V vs. 0.368 V vs. −0.023 V) and lower corrosion current density (Icorr: 6.76 ×10−7 A/cm2 vs. 7.946 ×10−7 A/cm2 vs. 8.91 ×10−7 A/cm2) for heat inputs of 235 J/mm, 281 J/mm, and 356 J/mm, respectively.

The influence of ferrite content, ferrite-austenite morphology, and orientation relationship on bainite transformation in intercritically annealed bainitic steels

This manuscript elucidates the influence of varying ferrite/tempered martensite (TM) content, morphology and orientation relationship (OR) between ferrite/TM with reverted austenite (γ) resulting at different intercritical temperatures on the subsequent bainite transformation behaviour. A comprehensive analysis was conducted using scanning electron microscopy, electron backscattered diffraction, and dilatometry. TM/bainite and ferrite/bainite steels were produced through intercritical annealing at 735 °C, 745 °C, and 765 °C, followed by austempering at 310 °C, using initially quenched and cold-deformed martensite, respectively. In samples without cold rolling, TM and bainite are alternately distributed at all intercritical temperatures. The γ reversion process in these samples led to the formation of acicular γ at prior martensite blocks and laths while globular γ was formed at prior γ boundaries and packet boundaries. Notably, a lower TM content correlated with increased globular γ formation. The acicular γ exhibited a Kurdjumov–Sachs (K-S) OR with prior γ. The globular γ formed at prior γ grain boundaries showed the K-S OR with the prior γ where it grows. However, globular γ formed at packet boundaries maintained the K-S OR with one of its surrounding blocks in prior γ where it lies. In the subsequent austempering process, bainite formed from reversed γ followed the K-S OR with TM. The TM and bainite shared the same variant in the same block. In samples with cold rolling, polygonal ferrite and bainite were distributed at all intercritical temperatures. Decreasing the ferrite content showed a coarsening of the microstructure. All polygonal samples revealed an irrational OR between bainite/martensite and ferrite. In samples with and without cold rolling, the bainitic formation rate decreased with increasing ferrite/TM, likely due to the high C and Mn content at the α/γ interface. Comparatively, the samples without cold rolling showed faster bainitic transformation than samples with cold rolling at similar ferrite/TM percentages, particularly noticeable at higher ferrite/TM content. The alternately arranged elongated TM and reversed γ lamellae increased the α/γ interfacial density for bainitic nucleation. Moreover, K–S oriented α/γ interfaces exhibited a lower activation energy for bainite nucleation. In samples without cold rolling, both high density of α/γ interfaces and K–S oriented α/γ interfaces collectively facilitate the bainitic transformation.

A NOVEL DOUBLE-SIDE LASER WELDED THICK PLATE: MICROSTRUCTURE AND NUMERICAL PREDICTION OF TENSILE TEST

The study aims to provide firsthand knowledge on finite element simulation (FES) of double-side laser welded (LW) stainless steel 304 (SS-304) thick plates used for automobile application. Double-side welding technique is an idea of achieving complete penetration with minimal heat input. The microstructural evaluation revealed the presence of dendritic growth that results in the enhancement of tensile strength (TS) for the welded sample. There is a slight increase in the delta ferrite content in weldment. The change in microstructure is due to thermal history during solidification. The TS of base metal (BM) was [Formula: see text][Formula: see text]MPa whereas the welded sample exhibited strength of [Formula: see text][Formula: see text]MPa. FES was successfully employed to simulate TS with error percentage less than 1.

Effects of Autogenous Gas Tungsten Arc Welding (GTAW) on Corrosion Resistance of Stainless Steel 316L

The autogenous manual gas tungsten arc welding (GTAW) process was used for cladding austenitic stainless steel 316L using a single pass with various contact tip-to-work distances (CTWDs). Immersion and electrochemical tests were used to evaluate the corrosion resistance of the welded specimens, and a microstructural analysis was conducted to investigate the chemical composition of the molten pool and the heat-affected zone of welding. The key findings of this study indicate that the corrosion resistance improved under a CTWD of 5 mm due to the optimal distribution of ferrite and a refined microstructure. Additionally, the highest hardness was observed in specimens with a CTWD of 3 mm, attributed to the increased ferrite content in the weld metal. As the CTWD increased, the ferrite fraction decreased, and the hardness also diminished. However, in the CTWD 7 mm case, the higher heat input influenced the microstructure and molten pool shape significantly through the Marangoni effect, resulting in a lower corrosion resistance. These results suggest that optimizing the CTWD can enhance the corrosion resistance of welded 316L stainless steel.

Enhanced multiferroic properties of NZCFO-BNFSO composites: Synthesis, characterization, and performance analysis

The structural and multiferroic properties of xNi0.24Zn0.58Cu0.18Fe2O4(NZCFO)-(1-x)Bi0.9Nd0.1Fe0.95 Sc0.05O3(BNFSO) are explored in this paper. Bi2O3 additives significantly lower the sintering temperature of the composites. The XRD analysis validates the coexistence of hexagonal perovskite BNFSO and spinel NZCFO phases. The FESEM images illustrate an almost homogeneous amalgamation of the BNFSO and NZCFO grains. The real part of initial permeability and the relative quality factor increases with NZCFO contents in the composites. The maximum permeability is observed for the composite with 80 % ferrite content. The ferroelectric BNFSO exhibits antiferromagnetic behavior and with the increase in NZCFO the saturation magnetization increases significantly. The dielectric constant confirms typical dielectric dispersion at low frequencies because of Maxwell–Wagner space charge polarization. The P-E hysteresis measurement reveals that the composite with 40 % ferrite content exhibits the highest loop area and hence a large energy storage capacity. Incorporating BNFSO and NZCFO into the composite boosts the multiferroic properties, which might be a suitable alternative to single-phase multiferroics.

Design of Quenching and Tempering Process and Elucidation of the Relationship between Microstructure and Properties of 20Mn2SiNiMo Bainitic Wheel Steel

The rapid development of train transportation toward higher speed and heavier load requires superior wheel materials with high strength and toughness. Herein, a 20Mn2SiNiMo bainitic wheel steel is developed and bainitic wheels are produced. The quenching and tempering process of bainitic wheels is studied considering the bainitic ferrite content and stability of retained austenite (RA). The quenching process includes water spraying and air cooling. Proeutectoid ferrite can be suppressed during the water‐spraying process. During air cooling, the bainitic ferrite transformation is promoted and the stability of RA is improved with the extension of cooling time. Corresponding microstructure of as‐quenched steel at wheel rim is bainite with different morphologies, martensite, and RA. The evolution of RA at lower and higher tempering temperatures is dominated by carbon enrichment and carbon consumption, respectively. Yield strength of bainitic wheel steel mainly comes from body‐centered cubic phase (containing martensite and bainitic ferrite). The increase of dislocation density and the decrease of effective grain size are beneficial for yield strength improvement. Bainitic packets with various direction, deformation‐induced martensite transformation of RA, and plastic deformation all play an important role in enhancing the toughness of bainitic wheel steel.

Effect of Tempering Temperature on Microstructure and Intergranular Corrosion Property of 2205 Duplex Stainless Steel

The effect of tempering temperature on the microstructure and intergranular corrosion property of 2205 duplex stainless steel (DSS2205) was determined using a boiling acid intergranular corrosion test (boiling 65% nitric acid and 50% sulfuric acid–ferric sulfate), an optical microscope, a transmission electron microscope, and a double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. The results show that the ferrite content of the DSS2205 is about 50% in a specimen close to a solid solution state (1050 °C for 1 h, then water-quenched) when tempered at 675 °C–725 °C for 1 h. As the tempering temperature rises to 750 °C–800 °C for 1 h, the ferrite content drops gradually from 49% to 35%. M23C6, FeCr (σ phase), and Cr2N phases are precipitated when the specimen is tempered at 675°C–800 °C for 1 h. When the tempering temperature rises to 750 °C–800 °C for 1 h, the content and size of σ phase increase significantly. In the boiling acid intergranular corrosion test, when the specimen is tempered at 675 °C–725 °C for 1 h, the corrosion rate is higher than when it is tempered at 750 °C–800 °C for 1 h. In the DL-EPR test, when the specimen is tempered at 675 °C–800 °C for 1 h, the intergranular corrosion sensitivity rises gradually. External polarization is added during the DL-EPR test, and the test principle is different from that of the boiling acid intergranular corrosion test, resulting in a different sensitivity to intergranular corrosion compared to boiling acid intergranular corrosion.