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Quenching and partitioning (Q&P) treatment is a novel method to produce advanced high strength steel with excellent mechanical properties. In this study, combination of multiple-cyclic annealing and Q&P process was compared with traditional cold-rolled Q&P steel to investigate the microstructural characteristics and austenite retention. The results showed that retained austenite in traditional Q&P sample was principally located in the exterior of austenite transformation products, while those in multiple-cyclic annealing samples were mainly distributed inside the transformation products. With the increase in cyclic annealing number, both of austenite fraction and austenite carbon content increased, attributing to higher initial austenite carbon content and larger number of austenite/neighbored phase interface to act as carbon partitioning channel. In traditional Q&P sample, the deformed ferrite was recrystallized by sub-grain coalescence, while the austenite was newly nucleated and grew up during annealing process. As a comparison, the ferrite in multiple-cycle annealing samples was formed by means of three routes: tempered martensite that completely recovered with retention of interior martensite variant, epitaxial ferrite that formed on basis of tempered martensite, ferrite that newly nucleated and grew up during the final annealing process. Both of lath martensite and twin martensite were formed as initial martensite and then tempered during partitioning process to precipitate e carbide with C enrichment, Mn enrichment and homogeneous Si distribution. Compared with the traditional cold-rolled Q&P steel, the Q&P specimens after multiple-cyclic annealing show smaller strength and much larger elongation, ascribing to the coarser microstructure and more efficient transformation induced plasticity (TRIP) effect deriving from retained austenite with high carbon content and larger volume fraction. The application of double annealing treatment can optimize the mechanical properties of Q&P steel to show a striking product of strength and elongation as about 29 GPa%, which efficiently exploit the potential of mechanical performance in low carbon steel.

To accurately describe the adsorption equilibria of N2 and O2 on LiLSX zeolite in the design of air separation by pressure swing adsorption, an applicable model (aNRTL–RAST) was developed. It was b...

Increasing magnetically favorable //ND texture components is a key challenge in the preparation of high-efficiency non-oriented electrical steels. In this study, an Fe-1.3 wt% Si steel with strong Cube ({100} ) and Goss ({110} ) texture was successfully produced by novel twin-roll strip casting, cold rolling and annealing process. The microstructure and texture of the material was characterized by optical microscopy, electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). The origin and formation mechanism of texture are described from the perspective of deformation and recrystallization behavior of specifically oriented grains. It was observed that initial Cube rotated toward {013} -{110} besides rotation toward {001} -{001} during cold rolling. In addition, new Cube deformation bands were developed in the deformed {115} -{115} grains. Cube components were partly retained as large block, small band structure and crystallite after heavy cold rolling. The Cube deformation structures served as nucleation sites of new Cube grains. The shear band within {114} , {112} and {111} matrix also provided some Cube nuclei. Morphology change from near bar-shaped to equiaxed occurred during the growth of Cube and Goss grains. The formation of recrystallization texture is attributed to the oriented nucleation mechanism, and the orientation pinning and size effects that impacted the intensity of texture component. The low thickness of strip and coarse solidification microstructure with strong {100} texture are the decisive factors to obtain strong Cube and Goss texture in strip-cast non-oriented electrical steel.

A novel processing strategy was proposed, first to promote Mn partitioning behavior during intercritical annealing, second to improve the fraction and stability of retained austenite (RA) and third to enhance mechanical properties of Mn-reduced transformation-induced plasticity (TRIP) steel. By deliberately preparing large-fractioned Mn-enriched cementite before final annealing, the intercritical austenite was encouraged to inherit relatively high Mn content from pre-existing cementite. Eventually, the formation of sufficiently stable RA together with the precipitation of fine VC particles in ferritic matrix contributes to much better yield strength-tensile strength-ductility combination of 763 MPa-1022 MPa-46.4%, which is superior to many steels containing higher Mn concentrations.

Fe–6.5 wt% Si non-oriented electrical steel is an excellent soft magnetic material due to the low core losses at high frequencies and near-zero magnetostriction. In this study, an Fe–6.5 wt% Si non-oriented electrical steel was processed by hot rolling, warm cross rolling, intermediate annealing, warm temper rolling and final annealing. The evolution of microstructure and microtexture during final annealing was investigated using a quasi in situ EBSD (electron backscatter diffraction) technique. After warm temper rolling, an area on the ND–RD (normal direction–rolling direction) cross section was marked by micro-hardness indents, and the recrystallization of individual grains in this area was traced under EBSD when the annealing time was increased. Due to the differences in the microstructure, texture and stored energy after warm temper rolling, the surface and center regions showed different recrystallization behaviors. The recrystallization of the surface region was essentially initiated by the growth of existing crystallites having lower stored energy than their neighboring areas (essentially no nucleation), while the center region showed both nucleation and grain growth during annealing. The growth rates of individual grains were evaluated with respect to the number of neighboring grains, and they approximately followed the von Neumann–Mullins law of grain growth. The surface region showed a much faster growth rate than the center region. The final texture was dominated by //ND and //ND in both the surface and center regions, due to the preferred growth of these grains.

Cross rolling is an effective processing technique used to optimize the crystallographic texture of electrical steel sheets. However, it is usually applied in cold rolling only. It is unknown how this rolling technique affects the microstructure and texture of electrical steels at elevated temperatures. In this study, a two-stage warm cross rolling scheme, i.e., rolling at elevated temperatures and in alternative directions with respect to the hot rolling direction (HRD), was applied to an Fe-6.5 wt% Si non-oriented electrical steel to produce thin steel sheets. The swapping of rolling direction between the two warm rolling stages significantly changed the deformation microstructure and texture, leading to different final recrystallization textures. These differences are attributed to the discrepancies in slip activities at elevated temperatures and to the different initial textures resulted from the change in rolling direction. The magnetic properties of the final steel sheets are evaluated by single sheet testing. Although the steel processed by warm rolling along HRD in the first stage and along HTD in the second stage exhibits a slightly higher magnetic flux density than other routes, it is shown that the magnetic flux density and core loss may have little relation to the crystallographic texture since the magnetocrystalline anisotropy caused by the texture is small.

We applied two types of hot-rolling direct quenching and partitioning (HDQ&P) schemes to a low-C low-Si Al-added steel and obtained two ferrite-containing TRIP-assisted steels with different hard matrix structures, viz, martensite or bainite. Using quasi in-situ tensile tests combined with high-resolution electron back-scattered diffraction (EBSD) and microscopic digital image correlation (µ-DIC) analysis, we quantitatively investigated the TRIP effect and strain partitioning in the two steels and explored the influence of the strain partitioning between the soft and hard matrix structures on the TRIP effect. We also performed an atomic-scale analysis of the carbon partitioning among the different phases using atom probe tomography (APT). The results show that the strain mainly localizes in the ferrite in both types of materials. For the steel with a martensitic hard-matrix, a strong strain contrast exists between ferrite and martensite, with the local strain difference reaching up to about 75% at a global strain of 12.5%. Strain localization bands initiated in the ferrite rarely cross the ferrite/martensite interfaces. The low local strain (2%–10%) in the martensite regions leads to a slight TRIP effect with a transformation ratio of the retained austenite of about 7.5%. However, for the steel with bainitic matrix, the ferrite and bainite undergo more homogeneous strain partitioning, with an average local strain in ferrite and bainite of 15% and 8%, respectively, at a global strain of 12.5%. The strain localization bands originating in the ferrite can cross the ferrite/bainite (F/B) interfaces and increase the local strain in the bainite regions, resulting in an efficient TRIP effect. In that case the transformation ratio of the retained austenite is about 41%. The lower hardness difference between the ferrite and bainite of about 178 HV, compared with that between the ferrite and martensite of about 256 HV, leads to a lower strain contrast at the ferrite/bainite interfaces, thus retarding interfacial fracture. Further microstructure design for TRIP effect optimization should particularly focus on adjusting the strength contrast among the matrix structures and tuning strain partitioning to enhance the local strain partitioning into the retained austenite.

Experimental and simulation methods were applied to analyze the transformation kinetics of epitaxial ferrite (EF) formed during a continuous cooling process and relevant carbon content heterogeneity in a low-carbon quenching and partitioning steel, with an emphasis on the influence of austenite carbon heterogeneity issued from EF formation on subsequent martensite and bainite transformation behaviors. It revealed that EF transformation possessed a kinetic curve with sigmoid shape and accelerated with decreasing cooling rate. With EF/γ interface under negligible partition local equilibrium condition in Dictra simulation, the simulation EF transformation kinetics can reproduce the experimental results well and the partial inheritance of Mn and Si from austenite into EF was also predicted. Furthermore, martensite transformation behaviors (one-stage or two-stage transformation) significantly depended on cooling rate and were explained by the austenite carbon heterogeneity issued from EF formation. The increase in initial martensite fraction with elevating cooling rate accelerated the subsequent bainite transformation and was favorable to austenite retention as well.

The low carbon micro-alloyed steel with start microstructure of ferrite-martensite was pre-tempered to be ferrite-tempered martensite microstructure before cold rolling. Then an identical quenching and partitioning process was applied to the cold rolled sheet with start microstructures of deformed ferrite-martensite (Q&P-UFC) and deformed ferrite-tempered martensite (Q&P-T). It revealed that the austenitization of Q&P-T was retarded and much more austenite with higher stability was obtained after annealing. In both cases, the austenite formed at recrystallized martensite boundaries was significantly fine, while that formed at recrystallized ferrite boundaries was much coarser. Although the retained austenite fraction (5–6%) and corresponding carbon content (1.1–1.2 wt.%) were identical in both cases, a significant Mn-enrichment of retained austenite was only observed in Q&P-T related to the pre-existed Mn-enriched cementite and hence the corresponding TRIP effect in Q&P-T occurred at relatively larger strain. Moreover, abundant martensite variant combination with twin boundary was observed and exhibited dispersive distribution in Q&P-T. The work hardening behaviors of both cases showed three-stage variation, successively ascribed to the dislocation glide of ferrite, TRIP effect of retained austenite and dislocation intersection/tangle of ferrite and martensite, respectively. Both samples exhibited excellent combination of strength and ductility with UTS larger than 1000 MPa and TEL larger than 20%, and Q&P-UFC was favorable to obtain high strength level, while Q&P-T possessed better ductility and excellent combination of strength and ductility.

A novel ultra-high strength transformation-induced plasticity (TRIP) steels with submicron-size martensite/austenite (M/A) constituents was processed by non-isothermal annealing process and compared with quenching and partitioning (Q&P) steels. The microstructure was characterized by means of SEM equipped with EPMA, XRD, EBSD and TEM and its effects on tensile strength and ductility were studied. The non-isothermal annealing significantly refined the parent austenite grains and enhanced inhomogeneous distribution of C atoms within the grains. Moreover, a large fraction of M/A constituents were separated and refined to hundreds of nanometers through bainite transformation in TRIP steels, while blocky retained austenite mainly existed near the carbon-rich prior grain boundaries in Q&P steel. TRIP steels had a higher content of less stable retained austenite by isothermal bainite transformation than Q&P steel, thereby favoring for improving the ductility. The contribution of fresh martensite to the ultimate tensile strength increased gradually from 49.7% to 67.3% with increase in the volume fraction of fresh martensite in TRIP steels. Optimizing the volume fraction and size of M/A constituents was important to obtain a high ultimate strength with desired ductility. The excellent mechanical properties were obtained in TRIP-350 (austempering at 350 °C) with ultimate tensile strength of 1011 MPa, total elongation of 28.80% and the product of strength and elongation (PSE) of 29.1 GPa%, exceeded the properties of Q&P steel.

We applied a hot rolling direct quenching and partitioning (HDQ&P) process to a low-C low-Si Al-added steel and obtained a Q&P steel containing 40 vol % of ferrite. Microstructure characterization was performed by means of SEM, EBSD, TEM and XRD. Atomic-scale characterization of carbon partitioning among the phases was carried out by atom probe tomography (APT). The carbon distribution in the retained austenite and near the martensite/retained austenite interfaces was quantitatively analyzed to study its partitioning behavior. The macroscopic strain distribution evolution across the tensile sample surface was investigated using macro digital image correlation (DIC) analysis. Combining these results with joint micro-DIC and EBSD analysis during quasi in-situ tensile testing, we investigated the strain partitioning among the different phases and the TRIP effect. Coupling of these results enabled us to reveal the relation among carbon partitioning, strain partitioning and the TRIP effect. The large blocky retained austenite with a side length of about 300–600 nm located near the ferrite/martensite (F/M) interfaces has low stability and transforms to martensite during the early deformation stages, i.e. at average strain below 21%. The retained austenite films in the centers of the martensite regions are more stable. The carbon distribution in both, the martensite and the retained austenite are inhomogeneous, with 0.5–2.0 at. % in the martensite and 4.0–7.5 at. % in the retained austenite. Strong carbon concentration gradients of up to 1.1 at. %/nm were observed near the martensite/retained austenite interfaces. The large blocky retained austenite (300–600 nm in side length) near the F/M interfaces has 1.5–2.0 at. % lower carbon content than that in the narrow retained austenite films (20–150 nm in thickness). The ferrite is soft and deforms prior to the martensite. The strain distribution in ferrite and martensite is inhomogeneous, varying by up to 20% within the same phase at an average strain of about 20%. Ferrite deformation is the main origin of ductility of the material. The balance between ferrite fraction and martensite morphology controls the TRIP effect and its efficiency in reaching a suited combination of strength and ductility. Reducing the ferrite volume fraction and softening the martensite by coarsening and polygonization can enhance the strain carried by the martensite, thus promoting more retained austenite in the martensite regions enabling a TRIP effect. The enhancement of the TRIP effect and the decrease of the strain contrast between ferrite and martensite jointly optimize the micromechanical deformation compatibility of the adjacent phases, thus improving the material's ductility.

In this study, two types of as-cast microstructure produced by strip casting were cold rolled and annealed to investigate the effect of initial microstructure on the textural evolution and magnetic properties of non-oriented silicon steel. The results indicated that the cold-rolled sheets of coarse-grained strip with pronounced {100} components exhibited stronger λ fiber (〈100〉//ND) and weaker γ fiber (〈111〉//ND) texture as composed to the fine-grained strip with strong Goss ({110}〈001〉) texture. After annealing, the former was dominated by η fiber (〈001〉//RD) texture with a peak at {110}〈001〉 orientation, while the latter consisted of strong {111}〈112〉 and relatively weak {110}〈001〉 texture. In addition, a number of precipitates of size ∼30–150 nm restricted the grain growth during annealing, resulting in recrystallization of grain size of ∼46 μm in the coarse-grained specimen and ∼41 μm in the fine-grained specimen. Ultimately, higher magnetic induction (∼1.72 T) and lower core loss (∼4.04 W/kg) were obtained in the final annealed sheets of coarse-grained strip with strong {100} texture.

Bismuth vanadate (BiVO4) is one of the most promising metal oxide semiconductors for photoelectrochemical (PEC) water oxidation. Much efforts have been dedicated on accelerating the sluggish surface water oxidation kinetics. In this study, plasma enhanced atomic layer deposition and subsequent removal of Al2O3 ultrathin overlayers on bismuth vanadate were implemented to achieve the successful passivation of surface states and significant enhancement of PEC performance. Al2O3 ultrathin overlayers were first coated on BiVO4 surface via plasma enhanced atomic layer deposition with various deposition cycles, which resulted in the decrease of PEC water oxidation activity due to the poor conductivity. The subsequent removal of surface amorphous Al2O3 passivated the surface states of the photoanodes and significantly enhanced the photocurrent densities. The passivated BiVO4 exhibited a photocurrent density of 1.34 mA·cm−2 at 1.23 V vs. RHE, which is 73% higher than that of unmodified BiVO4. This work provides a novel strategy and deep insights on surface modification of semiconductor for photoelectrochemical energy conversion.

Polypropylene (PP) is one of the most widely used polymers. In this paper, three types of PPs including random PP, impact PP, and impact PP with high clarity, were prepared through a 75 kg/h pilot-scale Spheripol II process. The three produced PPs were produced by the selection or combination the two loops and gas phase reactor and controlling the comonomer and hydrogen concentrations. The three prepared PPs then were pelleted with the clarified nucleating agent NX 8000 and tested for mechanical, thermal, and optical properties. Their molecular structures and rubber phase size were also investigated by GPC, 13C NMR, temperature rising elution fractionation (TREF), XRD, SEM analysis, etc. The results showed that the random PP (PP-1) and the impact PP with high clarity (PP-3) obtained excellent optical transparency with a haze of 12.5% and 13.5% due to their small rubber phase size (roughly &le, 100 nm), while the impact PP (PP-2) obtained bad transparency with a haze of 98.8% due to the large rubber phase size (about 1 &mu, m) caused by the poor thermal compatibility with the PP matrix. The rubber phase content and ethylene/propylene sequence distributions of the three PPs varied much and resulted in different impact strengths and stiffness properties. PP-2 had a high impact strength of 14.5 kJ/m2 due to the rubber phase generated in the gas phase reactor. Except for the optical transparency, PP-3 gained stiffness and toughness, with 914 MPa of flexural modulus and 25.1 kJ/m2 of impact strength due to the unique molecular structure of its rubber phase.

The present study focuses on improving the magnetic properties and decreasing the anisotropy in non-oriented electrical steel by optimizing {1 0 0} recrystallization texture. As-cast Fe-1.3%Si strip with {1 0 0} texture produced by strip casting was subjected to hot rolling in the ferrite region, cold rolling, and recrystallization annealing. Magnetic properties and texture evolution after different stages of processing were studied. Annealed sample without hot rolling exhibited pronounced Cube and Goss texture, which led to high permeability but induced a large difference (∼0.15 T) in magnetic induction B50 between the maximum at 0° and minimum at 45° to the rolling direction. The introduction of hot rolling with 17–40% reduction weakened the intensity of recrystallization texture and had small influence on the nature of texture and magnetic induction. However, relatively complete {1 0 0} recrystallization texture was developed in the sample with hot rolling of 55% reduction. On the other hand, the average grain size of annealed sheets gradually increased with the increased hot rolling reduction. As a result, the magnetic induction and the core loss was optimized together with the improvement of anisotropy. The development of recrystallization texture is discussed on the basis of the deformed microstructure and nucleation mechanism, while the magnetic properties are correlated to the magnetic quality of the texture.

A high strength steel with Nb-V-Ti addition was heat treated by a series of isothermal bainite holding (IBH) processes and quenching and partitioning (Q&P) processes with different intercritical annealing temperatures. The microstructure observation showed that some martensite was formed during quenching in IBH condition with annealing temperature above 850 °C, mainly ascribed to heterogeneous carbon content distribution in parent austenite with relatively large size. Meanwhile, film-like RA in martensite, relatively coarser lath-like RA in bainite and blocky RA located in grain boundaries or phase boundaries were observed in both IBH and Q&P treatments. Moreover, Q&P process was proved to be more beneficial to retain austenite than IBH process, while the ability of austenite retention was similar in IBH conditions. An excellent combination of strength and ductility was obtained in Q&P process annealed at 880 °C with tensile strength of 1126 MPa and total elongation of ~ 18%, attributing to TRIP effect mainly occurred in the latter part of strain and fine microstructure with homogeneous distribution.

The kinetic models of multiple-stage martensite transformation and subsequent isothermal bainite formation were investigated in intercritical quenching and partitioning steels. The modified K-M model that considering instantaneous kinetic characteristics was established and can well describe the kinetics of respective stage of martensite transformation, which was explained as a synergistic result of transformation stress relaxation and austenite plastic accommodation. The selection and combination of martensite variants played a vital role in stress relaxation of stage-2 martensite transformation. The precipitation of ε carbide inside initial martensite was initiated during isothermal partitioning process, while cementite formation was entirely suppressed. Meanwhile, the ε carbide was confirmed to be significantly Mn-enriched, while no obvious difference in the distribution of Si element. Moreover, a modified model based on the dilatometric results excluding ε carbide precipitation was applied to describe isothermal bainite transformation kinetics and revealed that the autocatalytic effect is negligible in samples evaluated here. The accelerated effect of initial martensite on bainite transformation was ascribed to the pre-existed defect originated from martensite formation and was enhanced with the increase in initial martensite fraction. The bainite transformation kinetics with identical annealing condition and partitioning temperature evaluated here can be precisely predicted, irrespective of initial martensite fraction. Keywords: Quenching and partitioning steel, Multiple-stage martensite transformation, Isothermal bainite transformation, ε-Carbide, Kinetic model

We describe here the aging characteristics and strengthening behavior of a low-carbon medium-Mn Cu precipitation-strengthened steel. Atom probe tomography (APT) was employed to characterize the evolution of Cu-rich precipitates in terms of mean radius, number density and volume fraction. Aging at 500 °C and 550 °C for 1 h resulted in substantial coherent body-centered cubic (bcc) Cu-rich precipitates with mean radius of 1.35 and 2.59 nm, respectively. The precipitation strengthening mechanism for these two aging conditions was shearing mechanism and the corresponding strengthening contribution was ~ 266 and ~ 312 MPa, respectively. Here, coherency strengthening and modulus strengthening played a major role, while the contribution of chemical strengthening was relatively small. With increased aging temperature to 600 °C, the precipitates grew and coarsened to elongated shape with incoherent face-centered cubic (fcc) structure, and the strengthening mechanism was Orowan mechanism with a contribution of ~ 232 MPa. Increasing the aging temperature also facilitated the formation of retained austenite, which was of great benefit to plasticity without pronounced deterioration on precipitation strengthening. Ultra-high yield strength of 1020 MPa with superior total elongation of 25.8% was obtained in the sample aged at 600 °C for 1 h. The excellent mechanical properties derived from the combination of precipitation strengthening by Cu-rich precipitates and plasticity effect of retained austenite can be considered as a design principle to simultaneously optimize strength and ductility.

Fe-6.5 wt% Si steel hot bands with different initial grain size and texture were obtained through different annealing treatment. These bands were then warm rolled and annealed. An analysis on the evolution of microstructure and texture, particularly the formation of recrystallization texture was studied. The results indicated that initial grain size and texture had a significant effect on texture evolution and magnetic properties. Large initial grains led to coarse deformed grains with dense and long shear bands after warm rolling. Such long shear bands resulted in growth advantage for {1 1 3} 〈3 6 1〉 oriented grains during recrystallization. On the other hand, sharp {11 h} 〈1, 2, 1/h〉 (α∗-fiber) texture in the coarse-grained sample led to dominant {1 1 2} 〈1 1 0〉 texture after warm rolling. Such {1 1 2} 〈1 1 0〉 deformed grains provided massive nucleation sites for {1 1 3} 〈3 6 1〉 oriented grains during subsequent recrystallization. These {1 1 3} 〈3 6 1〉 grains were confirmed to exhibit an advantage on grain growth compared to γ-fiber grains. As a result, significant {1 1 3} 〈3 6 1〉 texture was developed and unfavorable γ-fiber texture was inhibited in the final annealed sheet. Both these aspects led to superior magnetic properties in the sample with largest initial grain size. The magnetic induction B8 was 1.36 T and the high frequency core loss P10/400 was 17.07 W/kg.

A low carbon steel microalloyed with Nb-V-Ti were heat treated by means of two-step quenching and partitioning (Q&P) process after partial austenitization. Combined use of SEM equipped with EBSD, XRD and TEM showed that the microstructure was composed of intercritical polygonal ferrite, tempered lath martensite, secondary twin martensite and carbon-enriched retained austenite, as well as microalloyed carbides (mainly VC) precipitated inside ferrite and martensite. When increasing partitioning time from 0 s to 3600 s, the volume fraction of retained austenite increased up to 6.5% with mean carbon content in austenite keeping a constant level. The retained austenite kept K-S orientation relationship with adjacent tempered lath martensite and neighboring secondary twin martensite in different martensite packet. As partitioning time increased up to 3600 s, the initial lath martensite tempered gradually to ferrite without any cementite formation.

The effect of rolling temperature on the evolution of microstructure, texture, and magnetic properties of ultra-low-carbon grain-oriented silicon steel was studied in strip-casting process. Dynamic strain-aging (DSA) behavior was observed during warm rolling in the temperature range of ~ 200 to 400 °C based on the fact that majority of the inhibitor elements remained in solution during the strip-casting process. Considering the initial coarse grains with strong {100} fiber prior to rolling, the cold-rolled specimen exhibited pronounced α-fiber and weak γ-fiber texture. However, intense shear bands and high stored energy regardless of the orientation were obtained in the warm-rolled specimens at the DSA temperature, accompanied by weak α-fiber and strong γ-fiber texture. While homogenous microstructure with lower stored energy was observed in the case of high temperature, the differences in shear bands and stored energy governed by the rolling temperature were strongly related to the extent of DSA effect, which is attributed to distinct characteristic of rolling and recrystallization texture. After recrystallization annealing, fine-grained homogeneous microstructure with strong Goss and γ-fiber texture was obtained at the DSA temperature, while relatively random texture with much more α-fiber and θ-fiber components was observed in the case of high temperature. The microstructure and texture of primary annealed sheets exhibited sufficient Goss grains and favorable surrounding matrix with pronounced γ-fiber texture, which was responsible for the perfect secondary recrystallization annealing in the warm-rolled specimens at the DSA temperature. The present study suggests that texture optimization of strip-cast grain-oriented silicon steel can be achieved by warm rolling in the appropriate temperature range, with improved magnetic properties.

We elucidate the influence of intercritical rolling temperature on the microstructural evolution, mechanical properties and work-hardening behavior of a hot-rolled Fe-0.2C-6.5Mn-3Al-0.1V medium Mn transformation-induced-plasticity (TRIP) steel containing δ-ferrite. Tensile strength of 966 MPa, total elongation of 42.6% and yield strength of 705 MPa was obtained in the annealed steel subjected to a low intercritical rolling temperature. Rolling at a high intercritical rolling temperature promoted the partitioning of Mn from δ ferrite to prior austenite grains, and led to a martensitic matrix characterized by a fine lath structure. Subsequently, after intercritical annealing, the reversed austenite transformed from the martensitic matrix had high stability and small size. However, the reversed austenite with a high degree of Mn enrichment, fine lath structure and high stability provided a slow and less active TRIP effect. This was responsible for low work-hardening rate during deformation. In contrast, the high content of reversed austenite in the annealed steel subjected to low intercritical rolling temperature had relatively low stability and large lath width, exhibited serrated work-hardening behavior indicative of discontinuous TRIP effect. Additionally, the low intercritical rolling temperature led to a high density of dislocations in δ-ferrite, which effectively promoted VC precipitation after intercritical annealing, and enhanced yield strength. Furthermore, the formation of high angle boundary in δ-ferrite and the formation of pro-eutectoid ferrite at low intercritical rolling temperature also enhanced yield strength through grain boundary strengthening.

A low carbon C-Mn-Si-Al steel was hot rolled with coiling temperatures ranged from 510 oC to 710 oC. The microstructure of specimens consisted of deformed ferrite, lath martensite, twin martensite and bainite. Cementite was only observed in sample coiled at 570 oC. With increasing coiling temperature, deformed ferrite fraction decreased and recrystallized ferrite fraction increased. The ultimate tensile strength increased gradually from 1084 MPa to 1183 MPa due to the increasing fraction of martensite and bainite. The optimal mechanical properties were obtained when coiled at 570 oC with an ultimate tensile strength of 1085 MPa and ultimate elongation of 19.1 %.

Texture optimization has always been a challenge to fabricate non-oriented electrical steels (NOES). In the present study, thin-gauge NOES with high permeability was successfully processed using an innovative and convenient twin-roll strip casting process without hot rolling. The relation between the as-cast microstructure, processing route and texture evolution was studied. The results indicated that as-cast strip with coarse grains exhibited strong {100}〈0vw〉 texture and unique {110}〈110〉 component. Annealed sheets processed by one-stage rolling displayed pronounced {111}〈112〉, {223}〈110〉 components and weak Cube and Goss texture. Micro-texture characteristics revealed that {100}〈0vw〉 texture was partially retained from initial grains, and new Cube and Goss substructures were generated within {110}〈110〉 deformed grains during cold rolling. This was responsible for the development of Cube and Goss recrystallization texture. Furthermore, the application of two-stage rolling not only reinforced these two behavior, but also accelerated the nucleation of η grains because of the increased shear bands in cold-rolled sheets. In this manner, an improved texture consisting of dominant η-fiber, weak γ-fiber and optimized magnetic properties (B50 = 1.72 T, P10/400 = 14.91 W/kg) were obtained. Keywords: Thin-gauge non-oriented electrical steel, Twin-roll strip casting, Microstructure, Texture, Magnetic properties

For a critical examination of matrix effect on the melting of confined ice, mesoporous silica (SBA-15) are synthesised and decorated with n-Alkyl and aminopropyl groups to tune the surface hydropho...