Microstructure Of Steel Research Articles

Effect of Rapid Heating and Quenching on Microstructure and Mechanical Properties of High Strength Low Alloy Steel

Effect of Rapid Heating and Quenching on Microstructure and Mechanical Properties of High Strength Low Alloy Steel

Effect of Different Heat Treatment Processes on Microstructures and Mechanical Properties of DP Steels

Effect of Different Heat Treatment Processes on Microstructures and Mechanical Properties of DP Steels

Electromagnetic responses on microstructures of duplex stainless steels based on 3D cellular and electromagnetic sensor finite element models

Electromagnetic responses on microstructures of duplex stainless steels based on 3D cellular and electromagnetic sensor finite element models

Effect of Cerium Content on Non–Metallic Inclusions and Solidification Microstructure in 55SiCr Spring Steel

The effect of cerium content (0, 0.011, 0.017, 0.075 wt%) on non-metallic inclusions and solidification microstructures of 55SiCr high-strength spring steel was experimentally studied, along with thermodynamic calculations. The results show that Ce addition changes the type and size of inclusions in this steel and influences the characteristics of the solidification microstructure. In the sample without Ce addition, the main inclusions are MnS, SiO2, SiO2–MnS, and CaO–SiO2–MgO, and the equiaxed ratio in the solidification structure is 44.63%. However, when Ce content increases to 0.011 wt%, the inclusions in the steel become mainly Ce–S, Ce–O–S, and a small amount of MnS, and the equiaxed ratio increases to 50.42%. As the Ce content increases to 0.017 wt%, the inclusions are predominantly Ce–S, Ce–O–S, and Ce–O–S–Ca, while some Ce–P and Ce–O–P–C inclusions are also observed. The equiaxed ratio increases to 67.63%, showing the best effect on heterogeneous nucleation during solidification. When Ce content in the steel reaches 0.075 wt%, the Ce-containing inclusions are Ce–S, Ce–O, Ce–P, Ce–P–O, and Ce–O–S–As, and the size becomes larger. The formation mechanism of inclusions is explained by Gibbs free energy calculations and thermodynamic diagrams.

Effect of boron content and quenching temperature on the microstructure and wear resistance of high boron steel

Abstract This article investigates the change rule of the microstructure, hardness and wear resistance of high boron steel containing 0.1 wt.% to 0.5 wt.% boron in the cast state and after quenching at different temperatures. The results show that the microstructure of cast high boron steel with different contents of boron is composed of pearlite, ferrite and eutectic boride, which has lower hardness and wear resistance, and the higher the content of boron, the higher the hardness and the better the wear resistance. After quenching at 900–1,000 °C, pearlite and ferrite change into a large number of lamellar martensite and a small amount of lath martensite. After high-temperature quenching at 1,050 °C, retained austenite appears in the microstructure in addition to martensite, and borides are partially dissolved. The hardness and wear resistance are significantly improved compared to the as-cast high boron steel. As the quenching temperature increases, the dissolution of boride is obvious, the hardness and wear resistance are firstly increased and then decreased. When the content of boron is 0.5 wt.% and the quenching temperature is 1,000 °C, the hardness reaches a maximum value of 59.0 HRC, and the abrasion resistance is the best.

Effect of Si on the Yield Strength of Medium-Carbon Steels Consisting of Ferrite and Pearlite

To enhance the intrinsic yield strength of the ferrite-pearlite microstructure that inevitably forms in a non-quenched-and-tempered steel for large structural components, this study analyzed the effect of adding Si. The resulting ferrite-pearlite microstructure in medium-carbon steels was examined, and the resulting increase in yield strength was interpreted based on strengthening mechanisms. Hot-rolled sheets of 0.3C-1.5Mn steels were fabricated with Si ranging from 0.22 to 2.21 wt. %. Austenitization was conducted at 880°C followed by slow continuous cooling, and ferrite-pearlite microstructures were formed. With increasing Si, the yield strength increased from 409.1 to 573.6 MPa. Although there was a negligible change in the austenitic grain size, the mean diameter of the ferritic grains decreased from 8.8 to 5.0 μm, while the mean interlamellar spacing of the pearlites decreased from 196.6 to 109.9 nm. Using these quantitative data about microstructural features and considering possible strengthening mechanisms, a model to predict yield strength was derived via a constrained optimization method. The resulting model indicated that the major mechanisms are the refinement of pearlitic interlamellar spacing and the solid solution strengthening of ferrite by Si. Their contribution to the increment in yield strength was over 75 %, while others such as ferritic grain refinement and increased pearlitic volume fraction have limited influence.

Influence of Intercritical Annealing on Microstructure, Ductility, and Toughness of Medium Mn Steels

Influence of Intercritical Annealing on Microstructure, Ductility, and Toughness of Medium Mn Steels

Effect of Interlayer Temperature on Microstructure and Properties of High-Strength Low-Alloy Steel Manufactured Using Submerged-Arc Additive Manufacturing (SAAM)

Controlled interlayer temperature has a profound impact on both the microstructure and mechanical properties of the deposited components. In this study, thin-walled structures made of high-strength low-alloy steel were fabricated using the submerged-arc additive manufacturing process. The effects of varying temperature on the microstructure and mechanical properties of the components were studied. The results showed that the cooling rate within T8/5 decreased as the interlayer temperature increased, which caused the microstructure to transition from a fine-grained structure dominated by bainitic ferrite and granular bainite to a coarse-grained structure dominated by polygonal ferrite. The measurement of mechanical properties showed that due to the influence of the fine-grained structure, the components with low interlayer temperatures exhibit excellent hardness, high strength, and outstanding ductility and toughness. Furthermore, a faster cooling rate disrupts the stability of carbon diffusion, resulting in the development of increased quantities of residual austenitic films within the components with controlled low interlayer temperatures. This augmentation in residual austenite films strengthens the components’ ductility and toughness, enabling the deposited components to exhibit exceptional impact toughness in low-temperature environments.

Effect of alternative magnetic fields with different intensities on microstructure and mechanical properties of M50 steel during vacuum arc remelting

Effect of alternative magnetic fields with different intensities on microstructure and mechanical properties of M50 steel during vacuum arc remelting

Effect of heat treatment process on microstructure and properties of copper modified 1Cr11MoNiW1VNbN

Abstract The purpose of this study was to investigate the effects of Cu element content and heat treatment process on the microstructure and mechanical properties of 1Cr11MoNiW1VNbN martensitic heat-resistant steel. Microstructure was characterized by optical microscope (OM) and scanning electron microscope (SEM), tensile testing machine and impact testing machine were used to test the mechanical property. The results show that with the increase of Cu content, the precipitation of Cu-rich phase in the steel increases, while the formation of δ-ferrite and coarse carbides decreases, which significantly improves the strength of the material. When the Cu content is 2.14%, the tensile strength at 600 °C reached 542 MPa and the yield strength reached 484 MPa after normalizing at 1000 °C and tempering at 700 °C. With the increase of the normalizing temperature, the strength of the test steel decreases slightly, and the impact energy improved significantly.

Synergistic inhibition to dissolution corrosion by de-twinning and precipitation in alumina-forming austenitic steel exposed to lead-bismuth eutectic with 10-8 wt.% oxygen at 600°C

This work investigated the original microstructure of cold-worked alumina-forming austenitic steel, along with its precipitation and dissolution corrosion behaviors in lead-bismuth eutectic with 10-8 wt.% oxygen at 600°C, using solution-annealed steel for comparison. Anomalously, cold-worked steel presented milder corrosion compared to solution-annealed steel, with average corrosion depths of 314.3 and 401.0 μm after 1700 h exposure. Cold working-induced de-twinning transformed the annealing twin boundaries into normal high-angle grain boundaries (NGBs), increasing NGBs proportion from 36% to 89%. The increased NGBs provided more nucleation sites for intergranular barriers composed of alternate NiAl and M23C6 precipitates, thus better obstructing the dissolution attack.

The effect of microstructure of an advanced duplex stainless steel on the pitting corrosion and chloride-induced stress corrosion cracking resistance

The effect of austenite morphology on the corrosion resistance of a newly-developed advanced duplex stainless steel (ADCS) was evaluated by electrochemical and chloride-induced stress corrosion cracking (CISCC) tests. By properly controlling heat treatment conditions, equiaxed (EQ) and elongated (EL) austenites were formed in ferrite matrix. ADCS-EQ exhibited higher pitting potential than ADCS-EL, primarily owing to less phase boundary. Meanwhile, ADCS-EL showed better CISCC resistance than ADCS-EQ, as the elongated austenite inhibited selective dissolution. Overall, the CISCC resistance of ADCS was more affected by austenite morphology and orientation, and would not be in accordance with pitting corrosion resistance.

Effect of the flow behavior and dynamic recrystallization of EH420 marine steel on the morphology evolution of martensite substructures

The hot deformation behavior of EH420 marine steel was investigated by isothermal compression tests in the temperature range of 850~1050°C and the strain rate range of 0.01~10s−1. A high-temperature constitutive model and a hot processing map were developed. The results indicated that the microstructure of EH420 marine steel after hot deformation was mainly bainite and lath martensite. The martensite blocks gradually coarsened with the increase in temperature within the range of 950~1050°C/0.01s-1, and the average width increased from about 0.7 μm to 2.3 μm. At high strain rates, martensite blocks became coarse and disordered due to flow instability. The flow stress curve showed a single peak when the strain rate was low. There were more dynamic recrystallization (DRX) structures, resulting in fine and ordered martensite blocks. Under the deformation conditions of 0.1~10s-1/1000°C, the proportion of high-angle grain boundaries (HAGBs) decreased from 53.5% to 40.7% as the strain rate increased. Meanwhile, the hot deformation mechanism shifted from discontinuous dynamic recrystallization (DDRX) to the combined effect of DDRX and dynamic recovery (DRV) and finally transformed into DRV. The flow stress derived from the constitutive model was consistent with the experimental results. The activation energy of EH420 marine steel was 3.16×105J/mol. The optimal hot processing parameters were 950~1050°C and 0.01~0.1s-1.

Control of the concentrated-precipitation behaviour of Cr23C6 and its effect on the microstructure and properties of S600E sorbitic stainless steel

Control of the concentrated-precipitation behaviour of Cr23C6 and its effect on the microstructure and properties of S600E sorbitic stainless steel

Investigation of Microstructure and Mechanical Property Evolution in a Novel Low-Cost Ni-Free Maraging Steel Based on Mn and C through Cold Rolling Followed by Aging

Investigation of Microstructure and Mechanical Property Evolution in a Novel Low-Cost Ni-Free Maraging Steel Based on Mn and C through Cold Rolling Followed by Aging

Synergistic regulation of nano-precipitates and reversed austenite in titanium-free maraging steel by low-temperature solution treatment and double aging treatment

To synergistically enhance the strength and toughness of titanium-free maraging steel, a multi-scale characterization method was used to illustrate the effects of low-temperature solution treatment and double aging treatment on the microstructure of titanium-free maraging steel in this paper. After the low-temperature solution treatment and the double aging treatment, the tensile strength of titanium-free maraging steel increased from 1954 MPa to 2160 MPa and the elongation increased by 8.95 %. By the low-temperature solution treatment, the original austenite grain size of the titanium-free maraging steel was refined to 0.69 μm. The double aging treatment promoted the diffusion of Mo and Ni elements, increased the volume fraction of ω phase, Ni3Mo nano-precipitation phase and reversed austenite, and refined the size of ω phase and Ni3Mo by 14.2 % and 7.9 %, respectively. The nanoparticles of titanium-free maraging steel mainly include the ω phase, Ni3Mo and Laves phase. The strengthening mechanism of nanoparticles was quantitatively evaluated from the shear mechanism and Orowan dislocation loop mechanism. The mechanism shows that the ω phase is the main contributor to the overall precipitation strengthening. Therefore, low-temperature solution treatment and double aging treatment provide a potential solution for achieving high strength and high toughness in maraging steel.

Influence of Solid Solution Time on Microstructure and Precipitation Strengthening of Novel Maraging Steels

Effective subsequent heat treatment is crucial for achieving the desired microstructure and excellent mechanical properties in laser-deposited high-performance maraging steel. In this paper, we systematically investigate the synergistic relationship and tuning mechanism of different solution treatment times on the microstructure-property synergy of new maraging steels fabricated using laser direct energy deposition (LDED). To determine the optimal heat treatment process, solution treatment was conducted at 840°C for varying durations, followed by aging at 530°C for 2 hours to induce precipitation strengthening. The results indicate that after 2 hours of solution treatment, the alloy exhibits optimal ductility with an elongation of 7.90% ± 0.15%, attributed to the refinement of the martensitic matrix and precipitated phases, along with the formation of a small amount of residual austenite. When the solution treatment time is extended to 4 hours, the alloy achieves its highest tensile strength, reaching 1958 ± 24 MPa. However, the elongation decreases to 7.31% ± 0.12% due to the coarsening of the martensite and secondary phase particles. After 6 hours of solution treatment, significant coarsening and aggregation of the martensite and Fe2Mo intermetallic compounds markedly reduce the hardness, strength, and toughness of the alloy. By adjusting the solution treatment time, the size, morphology, and distribution of the martensitic matrix, Fe2Mo, and nanoscale precipitated phases play a critical role in the strengthening and fracture processes. Therefore, optimizing the precipitation behavior of the martensitic matrix and Fe2Mo intermetallic compounds through rational solution heat treatment is key to enhancing the mechanical properties of laser-deposited new maraging steels.

Mechanistic understanding of banded microstructure and its effect on anisotropy of toughness in low carbon-low alloy steel

In this study, the relationship between the anisotropy of toughness and microstructure in low carbon low alloy steel treated by quenching and tempering (QT) heat treatment was investigated with the aid of scanning electron microscope, electron back-scattered diffraction and transmission electron microscope combined with energy disperse spectroscopy techniques. Results show that the impact toughness of the quenched steel plate along the longitudinal and transverse directions are little different. However, after tempering, the longitudinal impact toughness of QT steel plate is improved by 88%, while the transverse impact toughness is slightly decreased, leading to a significant anisotropy of toughness. Microstructural characterizations reveal that banded microstructure with coarse grain size exists along longitudinal direction (i.e., rolling direction) of steel plate, which is attributed to co-segregation of Mn and C and the resulting uneven recrystallization during hot rolling. After tempering, fine and dispersed carbides are precipitated in matrix microstructure, but high-density coarse carbides are formed within banded microstructure. It is suggested that the coarse grains and high-density coarse carbides significantly deteriorate the resistance against crack propagation along banded microstructure, leading to the anisotropy of toughness of QT steel plate. The findings of this study will aid to design metallurgical processes including chemical composition design, hot rolling, and heat treatments to eliminate the anisotropy of toughness of low alloy steels with high strength and toughness.

Microstructure and material properties of 3D-printed bimetallic steels

Corroded steel components can be repaired by laser 3D printing technology. However, studies on the mechanical behaviour of repaired areas composed of a substrate and deposited material are still limited. In this study, 316L stainless steel powder was deposited on Q355B steel plates through 3D laser printing technology to form bimetallic steel plates. Uniaxial tensile tests were conducted on Q355B steel coupons, laser 3D-printed 316L stainless steel coupons, and bimetallic steel coupons. The test results revealed that ductile fracture occurred in the bimetallic steel coupons. The mechanical properties of bimetallic steel are considerably correlated with the properties of the cladding layer and substrate. During the loading process, the axial strain of the bimetallic steel coupons was uniformly distributed along the thickness direction, indicating that the substrate and cladding materials maintained excellent cooperative deformation. Bending tests and scanning electron microscopy observations indicate that a reliable and robust metallurgical bond is established at the interface between the substrate and the cladding layer. The interface area can be divided into the cladding layer, the carburising zone, the decarburised zone, and the Q355B substrate. The microhardness results indicate a considerable increase in the hardness of the carburised layer, which enhances the tensile strength of the bimetallic steel. On the basis of the experimental results, a three-stage model for predicting the stress‒strain curve of bimetallic steel was established.

Wetting behaviour of nickel-based brazing alloy BNi-5a on conventionally cast and laser-melted austenitic stainless steel 316L

Laser beam melting is an additive manufacturing process that enables the production of highly complex components. In this process, metal powder is locally melted using a laser beam and built up layer by layer to form a physical component. Due to the layer-by-layer process manufacturing technique of the additive manufacturing process, the microstructure of a laser-melted 316L austenitic stainless steel differs from that of a conventionally cast material. For brazing technology, the different microstructure morphology is important because it affects the known wetting and diffusion behavior with a brazing filler metal, which affects the ability to produce high-strength brazed joints. Brazeability can be determined by examining the wetting of the brazing filler metal with the material to be joined. Therefore, this study investigates the wetting behavior of nickel-base brazing alloy BNi-5a on conventionally cast and laser-melted 316L austenitic stainless steel. Wetting tests were performed to evaluate the spreading area and wetting angle of BNi-5a on both 316L substrates. The wetting tests were performed in a high-temperature vacuum furnace at 1190 °C for 15 min. The results show that the laser-melted 316L stainless steel exhibits enhanced wettability compared to the conventionally cast material. This is related to a higher surface energy and a more pronounced diffusion mechanism called grain boundary grooving on the surface of the material.