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In order to study the microstructure evolution and flow stress behavior of as cast antibacterial austenitic stainless steel containing 1.52 wt.% copper, Gleeble 3800 was used for thermal compression simulation test. Through OM and EBSD analysis, it is found that the dynamic recrystallization mechanism of thermal deformation is mainly discontinuous dynamic recrystallization. With the increase of deformation temperature and deformation rate, the proportion of recrystallization nucleation gradually increases. The growth of twins relies on recrystallization and, at the same time, promotes dynamic recrystallization. Considering the influence of strain on flow stress, the strain compensation Arrhenius model is established according to the obtained stress-strain curve, and high accuracy is obtained. The correlation coefficient and average relative absolute error are 0.979 and 7.066% respectively. These results provide basic guidance for the technology of microstructure control and excellent mechanical properties of antibacterial stainless steel.

An age-hardening cold-rolled ultrahigh-strength Fe-0.2C-7Mn-3Al-3Ni (wt.%) steel with large ductility was developed via intercritical annealing and followed by aging. It was observed that aging treatment not only resulted in high density nanosized NiAl intermetallic precipitate but it also strongly affected ferrite-austenite duplex microstructure especially the content and stability of austenite due to the partition of elements. Besides, it was found that aging treatment led to a simultaneous increase in both strength and total elongation, which was attributed to high-density NiAl nanoprecipitate, strong dislocation hardening, much stronger transformation-induced plasticity (TRIP) effect and the involvement of twinning-induced plasticity (TWIP) effect.

To study the effects of rare earth (RE) and Ti on the solidification microstructure of high borated stainless steels, 1.6 wt% B stainless steel doped with RE and 2.1 wt% B stainless steel doped with Ti were prepared by ingot casting, respectively. The solidification microstructure of researched steels was characterized in detail. The modification mechanism was clarified based on the heterogeneous nucleation theory and the thermodynamic calculation. The solidification microstructure of 1.6 wt% B and 2.1 wt% B stainless steels was characterized by the continuous and network-like eutectic borides around the matrix grains. It was found that the fine RE compounds could act as the heterogeneous nuclei for both borides and austenite during solidification. Thus, the eutectic borides were more dispersed in the modified steel. Moreover, lots of fine ‘eutectic cells’ were formed in the matrix regions. As a result of the preferential formation of TiB2 during solidification, the amount of the eutectic borides in the steel modified with Ti was significantly decreased. Besides, the continuity of the eutectic borides network was weakened. In a word, the present work provides a promising method to modify the solidification microstructure for high borated stainless steels.

High borated stainless steel sheets have been widely applied in the nuclear power industry because of good thermal neutron absorption property. However, the large and network-like borides existing around the austenite grains in the conventional ingot casting steel seriously deteriorate the hot workability and the mechanical properties at ambient temperature. In this work, we tried to acquire ultra-fine microstructure by sub-rapid solidification using a novel twin-roll strip casting technology so as to enhance the mechanical properties of 2.1%B austenitic stainless steel. Surprisingly, dispersive and very fine borides mostly smaller than 5 µm were produced in the as-cast microstructure without network-like distribution. The morphologies and crystal structure of borides as well as the stacking faults in borides were investigated in detail. After subsequent hot-rolling and solution treatment, ultra-fine borides were observed with more than 50% of which in a size range of 0.3–1.5 µm, significantly smaller than those of the conventional ingot casted and hot rolled steel. Benefiting from the ultra-fine borides, excellent mechanical properties which had not been reported were obtained. In particular, a total elongation of 14.1% was exhibited, which was twice as high as that of the conventional ingot casted and hot rolled steel. Thus a new structure-function combining high borated stainless steel sheet was achieved. The strengthening and plasticity increasing mechanism was discussed based on Hall-Petch relationship, Orowan mechanism and strain-hardening rate analysis. The fracture behavior in tensile deformation was studied in detail. A characteristic fracture process accompanied with the initiation and coalescence of cavities in austenite matrix was found. This work not only developed a new processing way to produce high borated stainless steel with excellent mechanical properties, but also provided a potential solution for some other hard-worked metallic materials with brittle eutectic phase.

In this paper, the complete electromechanical properties of the cellular-materials-based piezoelectric metamaterial are obtained by using micromechanical modeling method on the basis of the finite element. This study considers the piezoelectric star-shaped cellular structures (PSSCSs) with three connection modes (with symmetric interconnects, with asymmetric interconnects, and without any interconnects) and two poling directions (longitudinal and transverse). The representative volume units of three types of PSSCSs are established respectively, and the finite element analysis is implemented to the effect of different structural length parameters on the effective electromechanical response and the applicability of specific engineering applications. Compared with the monolithic piezoelectric materials, the PSSCSs show an enhanced performance combination. Besides, the results show that PSSCSs have adjustable electromechanical properties.

In the present work, the evolution of microstructure and texture and the resultant magnetic properties with different rolling reductions and intermediate annealing temperatures during two-stage cold rolling process were systematically studied. The one-stage cold rolling was also employed for comparison. It was found that finally annealed sheet fabricated by one-stage rolling exhibited pronounced α*-fiber ({h,1,1} ) and γ-fiber (〈111〉//ND) textures. By contrast, the two-stage rolling significantly weakened the unfavorable γ-fiber texture and enhanced the λ-fiber (〈100〉//ND), Goss ({110} 〈001〉) and near-Brass ({110} 〈112〉) textures in final sheets. Meanwhile, the introduction of intermediate annealing reduced the grain boundary density and deformation stored energy in secondly cold-rolled microstructure. The nucleation rate of recrystallization was hence decreased, thereby increasing the final grain size. Increasing intermediate annealing temperature in two-stage rolling process further optimized the recrystallization texture and increased the final grain size. It is noted that the γ-fiber texture in final sheets was gradually decreased with the decrease of second rolling reduction, while the λ-fiber texture and grain size were both increased firstly and then decreased. Eventually, an optimized combination of magnetic properties (B50 = 1.709 T, P15/50 = 1.828 W/kg, P10/400 = 11.92 W/kg) was obtained via a higher intermediate annealing temperature (950 °C) and an appropriate second rolling reduction (75%). Furthermore, the deformation and recrystallization behaviors of specifically oriented grains (i.e., λ-, Goss and near-Brass grains) were discussed in detail.

In the nuclear fuel reprocessing systems, the demands for high borated stainless steels are increasing due to their excellent thermal neutron shielding properties. However, the eutectic borides precipitating around the matrix grains could easily result in the severe edge cracking for the ingot-casting steels during processing. In this paper, a 3-layered composite plate consisting of 2.1 wt% B stainless steel and boron-free austenite steel was fabricated by welding and hot-roll-bonding. Besides, the microstructure evolution and the tensile properties of the composite and non-composite plates were comparatively investigated. It was found that the edge cracking of the composite plate was significantly suppressed comparing with the non-composite plate prepared by conventional hot rolling. Moreover, the ductility of the composite plate at room-temperature was greatly enhanced. The tensile elongation reached to 15.5% for the specimen after 1100 °C × 30 min solution treatment, and that was approximate 2.5 times as high as the elongation of the non-composite specimen. In addition, the inhibition mechanism of edge cracking during hot-roll-bonding, and the enhancement mechanism of tensile plasticity for the composite plates were both explained. The present work not only develops a new high borated stainless steel with the excellent mechanical properties, but also provides a promising method to suppress the edge cracking for some other metallic materials with poor hot workability.

0.05–0.15 mm-thick ultra-thin grain-oriented silicon steel sheets were successfully produced by a novel processing route including strip casting, hot rolling, normalizing, two-stage cold rolling with intermediate annealing, primary recrystallization annealing and secondary recrystallization annealing. The evolutions of microstructure, texture and inhibitor along the processing were briefly investigated. The results showed that the initial Goss orientation originated due to the heterogenous nucleation of δ-ferrite grains during solidification. Because of the lack of shear deformation, only a few Goss grains were observed in the hot rolled sheet. After the first cold rolling and intermediate annealing, Goss texture was enhanced and distributed in the whole thickness. A small number of Goss grains having a high fraction of high energy boundaries exhibited in the primary recrystallization annealed sheet. A large number of fine and dispersed MnS and AlN and a few co-precipitates MnS and AlN with the size range of 10–70 nm were also observed. Interestingly, a well-developed secondary recrystallization microstructure characterized by 10–60 mm grains and a sharp Goss texture were finally produced in the 0.05–0.15 mm-thick ultra-thin sheets. A magnetic induction B8 of 1.72–1.84 T was obtained. Another new finding was that a few {2 3 0}〈0 0 1〉 and {2 1 0}〈1 2 7〉 grains also can grow up abnormally because of the high fraction of high energy boundaries and the size and number advantage, respectively. These non-Goss grains finally deteriorated the magnetic properties of the ultra-thin sheets. In addition, low surface energies of {hk0} planes may also contribute to the abnormal growth of Goss, {2 3 0}〈0 0 1〉 and {2 1 0}〈1 2 7〉 grains.

The compression-torsion conversion (CTC) behavior of a novel cylindrical mechanical metamaterial is studied in the present paper. The structure is composed of arrayed askew re-entrant cells that originate from the traditional re-entrant cell. The effects of geometrical parameters such as the shape of askew re-entrant cells, the cell number in each layer and the radial thickness of the structure on the CTC efficiency are investigated via finite-element simulations and experiments. The numerical results indicate that the shape of the askew re-entrant cells mainly determines the CTC efficiency. Moreover, the proposed structures are fabricated utilizing additive manufacturing technology. Research results show that the cylindrical mechanical metamaterial features excellent CTC property.

This paper presents the non-local theory solution to a three-dimensional rectangular permeable crack in magneto-electro-elastic materials (MEEMs) using the generalized Almansi's theorem and the Schmidt method. The problems are formulated through Fourier transform as three pairs of dual integral equations, in which the unknown variables are the jumps of elastic displacement, electric potential and magnetic potential jumps across the crack surfaces. The displacement jumps across the crack surfaces are directly expanded as a series of Jacobi polynomials to solve the dual integral equations and the resulting equations are solved using the Schmidt method. Numerical examples are provided to show the effects of the geometric shape of rectangular crack and the lattice parameter on the stress, the electric displacement and the magnetic flux fields near the crack edges in magneto-electro-elastic materials. Unlike the classical solution, the present solutions exhibit no stress, electric displacement and magnetic flux singularities near the crack edges in magneto-electro-elastic materials.

This study deals with the mechanical behavior of a shear thickening fluid–sliding friction (STF–SF) isolator, and investigates the feasibility of its application in anti-seismic engineering from a theoretical perspective. The STF–SF isolator is composed of a conventional sliding friction (SF) material and a smart shear thickening fluid (STF) material. When the excitation energy is small, the SF material keeps the structure static or only has a small vibration. However, when the excitation energy is large, the STF material results a huge damping force and dissipation of the external energy, eventually reducing the relative motion between the base and the upper structure. To better understand this phenomenon, a mechanistic study of the STF–SF isolator is proceeded by an analytical model which is derived from flow momentum equations. After that, the seismic protective effect of the STF–SF isolator is evaluated at harmonic excitation with different accelerations through a single degree of freedom (SDOF) structure. Furthermore, the effects of layer gap, layer number and friction coefficient of the STF–SF isolator on the seismic protective effect are investigated. The results show that the STF–SF isolator can significantly decrease both the displacement response and the acceleration response of the SDOF structure. This theoretical study indicates the STF–SF isolator can be used in anti-seismic engineering.

Lattice metamaterials have a great prospect in many application fields such as vibration control, noise reduction and sound insulation. In this work, a novel lightweight bidirectional re-entrant lattice metamaterial (BRLM) is proposed based on the square lattice metamaterial. Band structures of the BRLM are calculated through the finite element method and Bloch’s theorem. The simulation results show that the broad bandgaps in the low frequency range are generated by rationally changing the geometrical parameters. The effects of geometrical parameters on the band structures, formation mechanics of the first bandgap and total effective bandgap width are investigated. The influence of damping on the transmission loss and bandgap distribution is also studied.

A high-Mn high-Al steel generally exhibits ultra-high ductility but low yield strength. Here, we report a way to control the precipitation of B2 and κ-carbide via annealing and subsequent aging in a Fe-16Mn-9Al-0.8C-3Ni (wt%) steel. The main purpose is to acquire refined and homogeneously distributed B2 and κ-carbide simultaneously so as to improve the strength–ductility balance. The microstructure of annealed sample consists of austenite, micron-sized polygonal B2 along austenite grain boundaries (GB-B2) and intra-granular B2 (mainly concentrates at 300–600 nm) in austenite (IG-B2). Aging results in high-density and fine IG-B2 particles (mostly smaller than 300 nm) and nano-scaled κ-carbides in austenite. Besides, a large amount of 30–220 nm sized κ-carbide precipitates within GB-B2 after aging at 600°C for 5 min. As a result, the precipitation strengthening of IG-B2 and κ-carbide particles as well as additional order strengthening of nano-scaled κ-carbides in austenite can dramatically increase yield strength by approximately 40% (~300 MPa) with no deterioration of ductility. However, a longer aging time (60 min) not only coarsens the κ-carbides to 55–280 nm, but also leads to the precipitation of new κ-carbides (150–730 nm) at B2-austenite interface due to eutectoid reaction, which can seriously worsen ductility.

In non-oriented electrical steels, the initial hot rolled microstructure usually had important effects on the successive microstructure and texture development during cold rolling and annealing and the final magnetic properties. In this paper, we reported that the hot rolled microstructure of a 0.4 wt% Si steel could be controlled by designing Ar1 (γ/α phase transformation temperature), which was susceptive to the content of Al. Three steel slabs with different Al contents (0.41, 0.30 and 0.21 wt%) were produced and then subjected to the same hot rolling, cold rolling and annealing treatment in an industrial production line. Interestingly, it was found that, the heavily elongated deformed grains were reduced or even avoided in the hot rolled sheets by decreasing Ar1 with a slight decline of Al. As a result, after cold rolling and annealing, weak γ-fiber (〈1 1 1〉//ND) texture and bigger grains were obtained. Hence, the magnetic properties were significantly improved, i.e. high magnetic induction (B50) together with low iron loss (P1.5/50). The microstructure and texture evolutions of these three steels throughout the whole processing route were comparatively investigated in detail, and the effects on magnetic properties were discussed in terms of the classical loss separation theory. This work also provides a promising method to optimize the microstructure, texture and magnetic properties for other low silicon non-oriented electrical steels.

High borated steels have been applied in the nuclear power industry as excellent neutron-shielding materials, but their ductility was relatively low due to the large and brittle borides, restricting their wider utilization. In this work, the high-performance borated steels containing 2.40 wt% B were fabricated through a designing combination of titanium-alloying along with twin-roll strip casting technology. It was found that titanium addition facilitated the increasing boron content of eutectic point for steels. The TiB2 particles solidifying firstly from molten steel depleted massive boron atoms in advance, leading to an as-cast microstructure consisting of more γ-Fe and less M2B-type borides comparing with titanium-free steels. Besides, TiB2 particles were 200–240 nm, and they could act as heterogeneous nucleation cores for M2B borides. Thus dispersive and fine M2B borides smaller than 5 μm were produced in as-cast microstructure. After subsequent hot-rolling and solution-treating, ultra-fine borides were obtained with more than 80% of which in a size range of 0.1–2 μm. In this case, the steels exhibited an excellent total elongation of 16.2% that was twice as high as that of titanium-free steels. Additionally, the relations between microstructure and mechanical properties of hot-rolled and solution-treated steels were clarified. The ductility of steels was determined by the volume fraction of γ-Fe matrix that could accommodate large deformation, but the strength of steels was dominated by the volume fraction of borides that provided the strengthening effects including grain refinement, load transfer term and hindering the dislocation slip. This work provided a new promising method to enhance the ductility of such high borated steels.

The composition and microstructure of silicon nitride fibers after heat-treatment at elevated temperatures were investigated by XRD, NMR, XPS, SEM and TEM analyses. The results show that as-received fibers consisted of amorphous silicon nitride, and a little Si-C-O structure. During heat-treatment process, α-Si3N4 and β-Si3N4 formed resulting from the crystallization of amorphous silicon nitride, and the formation of β-SiC derived from the decomposition of Si-C-O structure. As heat-treated temperature increased from 1400oC to 1600oC, the above phenomenon become obvious, indicating that the fiber would possess high serving life with serving temperature lower than 1400oC. The tensile strength of fibers stays stable when heat-treated temperature was below 1200oC, while the strength retention of fibers sharply decreased to 50% after heat-treatment at 1400°C.

The microstructure and texture evolution along the processing was investigated with a particular focus on the secondary recrystallization behavior in a 0.23 mm-thick twin-roll cast grain-oriented electrical steel. A striking feature is that Goss orientation originated during twin-roll casting as a result of shear deformation and it was further enhanced during hot rolling and normalizing. After primary recrystallization annealing, a homogeneous microstructure associated with a sharp γ-fiber texture was produced. During secondary recrystallization annealing, the γ-fiber texture was first strengthened and weakened with increasing temperature prior to the onset of secondary recrystallization. Goss grains always exhibited more 20–45° misoriented boundaries than the matrix. The matrix was quite stable during secondary recrystallization with the aid of dense inhibitors. Finally, a complete secondary recrystallization microstructure consisting of large Goss grains was produced. The grain boundary characteristics distribution indicated that the high energy model was responsible for the abnormal growth of Goss grains under the present conditions.

A 0.1 mm-thick grain-oriented silicon steel sheet was successfully produced using strip casting and three-stage cold rolling method. The microstructure, texture and inhibitor evolution during the processing was briefly analyzed. It was found that Goss texture was absent in the hot rolled sheet because of the lack of shear deformation. After normalizing, a large number of dispersed MnS precipitates with the size range of 15–90 nm were produced. During first cold rolling, dense shear bands were generated in the deformed ferrite grains, resulting in the intense Goss texture after first intermediate annealing. The microstructure was further refined and homogenized during the subsequent cold rolling and annealing processes. After primary recrystallization annealing, a homogeneous microstructure consisting of fine and equiaxed grains was produced while the associated texture was characterized by a strong γ-fiber texture. Finally, a complete secondary recrystallization microstructure consisting of entirely large Goss grains was produced. The magnetic induction B8 and iron loss P10/400 was 1.79 T and 6.9 W/kg, respectively.

The formation of Widmanstatten austenite was studied in strip cast grain-oriented silicon steel. The microstructure was investigated by optical microscopy and scanning electron microscopy. The orientations of the ferrite, Widmanstatten austenite, and martensite were determined using electron backscatter diffraction. The Widmanstatten austenite exhibits a lath-like shape and nucleates directly on the ferrite grain boundaries. This differs significantly from earlier work on duplex stainless steels. The orientation relationship between the Widmanstatten austenite and the parent ferrite is closer to Kurdjumov–Sachs than to Nishiyama–Wassermann. The ferrite boundaries migrate so as to accommodate the habit planes of the laths, leading to the presence of zigzag boundaries in the as-cast strip. Carbon partitioning into the Widmanstatten austenite and silicon partitioning into the parent ferrite were observed.

The high magnetic field induced regularly aligned zinc-rich plate-like cells during solidification of a Zn-27.6 wt%Sn alloy were investigated, along with the detailed analysis of crystallographic growth pattern. The results show that such plate-like cells were formed three-dimensionally and grew in the following pattern: a) a crystal grew out of the {0001} basal plane to form the horizontally extended primary trunks; b) the primary trunks branched vertically and then produced the 10 1 ¯ 0 > primary trunks; c) the 10 1 ¯ 0 > primary trunks branched again in the {0001} basal plane and created the high-order 10 1 ¯ 0 > arms, some of which then grew out of the {0001} basal plane for the next growth cycle. In such a repeated manner, a plate-like cell was finally formed.

In this work, a 0.71 wt%Si+0.44 wt%Al as-cast strip was produced by novel twin-roll casting. Some as-cast samples were respectively reheated and hot rolled at different temperatures in order to obtain different microstructure prior to cold rolling and annealing. The effects of the hot rolled microstructure on microstructure, texture evolution and magnetic properties were investigated in detail. A coarse deformed microstructure with λ-fiber texture was formed after hot rolling at 850–1050 °C, finally leading to an inhomogeneous recrystallization microstructure with strong λ-fiber, Goss and extremely weak γ-fiber texture. By contrast, a fine transformed microstructure was formed after hot rolling at 1150–1250 °C, finally leading to a fine and homogeneous recrystallization microstructure with stronger α-fiber, γ-fiber and much weaker λ-fiber texture. It should be noted that both the magnetic induction and core loss non-monotonically decreased or increased according to the hot rolling temperature. The unfavorable α-fiber and γ-fiber textures in the annealed sheets were much weaker than those of the conventional products regardless of the hot rolling temperature, thus contributing to a much higher magnetic induction. However, the average grain size in the annealed sheets was much lower than those of the conventional products regardless of the hot rolling temperature, thus leading to a higher core loss except the case of 1050 °C. Hence, it is underscored that better integrated magnetic properties than those of the conventional products can be obtained by optimizing the hot rolled microstructure to produce final desirable recrystallization microstructure and texture.

This paper investigates a functionally graded piezoelectric material (FGPM) containing two parallel cracks under harmonic anti-plane shear stress wave based on the non-local theory. The electric permeable boundary condition is considered. To overcome the mathematical difficulty, a one-dimensional non-local kernel is used instead of a two-dimensional one for the dynamic fracture problem to obtain the stress and the electric displacement fields near the crack tips. The problem is formulated through Fourier transform into two pairs of dual-integral equations, in which the unknown variables are jumps of displacements across the crack surfaces. Different from the classical solutions, that the present solution exhibits no stress and electric displacement singularities at the crack tips.

The oxide metallurgy was employed in the fabrication of twin-roll strip casting low carbon steels. The quantitative dependences of the microstructure and mechanical properties on cooling parameters were revealed and emphatically investigated. After twin-roll strip casting, a two-step cooling route closed to the actual process was designed and the cooling rates exhibited great influences on the proportion of polygonal ferrite (PF) and acicular ferrite (AF). With increasing cooling rates in both steps, the AF volume fraction raised from 0.04 to 0.75 because the rapid cooling restrained the formation of PF. The AF laths were induced by fine Al–Si–Ti–Mn composite oxides (0.2–2 μm), leading to a heterogeneous microstructure consisting of PF and AF clusters with high proportion of large-angle (≥15°) grain boundaries. It was found that the AF laths kept K–S relationship with austenite and AF laths with collinear growth direction belong to the same codirectional variants group in one AF cluster. With the increase of AF volume fraction, the yield strength (YS) and the ultimate tensile strength (UTS) were improved, while the strip retained excellent elongation. The improved YS was mainly ascribed to the grain boundary strengthening and dislocation strengthening.

The increase in casting slab thickness causes sharp increase in both the size and uneven distribution of brittle eutectic borides in high borated austenitic stainless steel, thus remarkably deteriorating the hot workability and the final room-temperature mechanical properties. Hence, it is undesirable to produce thick plates by rolling an extra-thick slab. Here it is reported that a specially designed hot-roll-bonding method for producing Fe–19Cr–15Ni-1.2B austenitic stainless steel thick plates using the conventional thick slab as starting materials. The main aim is to obtain refined and uniformly distributed borides so as to improve the room-temperature ductility and toughness by increasing total rolling compression ratio via hot-roll-bonding. It was validated that double-layered thick slabs could be successfully hot-roll-bonded though massive brittle ceramic (Cr,Fe)2B particles exist at the contacting interlayer interfaces. The hot-roll-bonding mechanism was clarified in terms of severe plastic flow, recrystallization and interface-diffusion. The effects of total rolling compression ratio on the morphological change and size distribution of (Cr,Fe)2B particles in both the mono-layered plates and the double-layered composite plates were investigated in details with the consequent effects on room-temperature comprehensive mechanical properties. It was found that the initial large and brittle (Cr,Fe)2B broke into more spheroidal and refined particles and significantly enhanced the ductility and toughness with increasing the total rolling compression ratio up to 10. The present work provides not only a practicable method to fabricate high borated austenitic stainless steel thick plates but also a promising way to improve the ductility and toughness of other metals containing a large number of hard and brittle particles.

Here we for the first time reported the heterogeneous nucleation of orthorhombic M2B-type borides (M = Cr, Fe) attached to TiB2 and Ti(C,N) particles with a specific crystallographic orientation relationship (OR) in as-cast boron-containing steel. The ORs were identified as 0001 Ti B 2 ∥ 1 ¯ 1 2 ¯ M 2 B , 1 2 ¯ 10 Ti B 2 ∥ 31 1 ¯ M 2 B and 001 Ti C N ∥ 13 6 ¯ M 2 B , 100 Ti C N ~ ∥ 3 1 ¯ 0 M 2 B . The transmission electron microscopy characterization and lattice misfit calculation showed that the interfaces of TiB2/M2B and Ti(C,N)/M2B were semi-coherent. The heterogeneous nucleation efficiency was investigated in terms of an interfacial energy calculation based on the misfit dislocation theory.

Effects of Mo-, Ti- and Nb-substitution for Al on the strength and damping capacity of the Fe-13Cr-4.5Al alloy were investigated by analyzing the mutual relationships among microstructures, strength, internal stress and damping capacity of the alloys. The obtained results show that the substitution of 0.5Mo for 0.5Al improves both the strength and damping capacity of the alloy. While the substitution of 0.5Ti or 0.5Nb for 0.5Al simply improves the strength but reduces the damping capacity of the alloy. The effect of the alloy elements on the strength and damping capacity lies in the fact that the substitution of the alloy elements generates both local internal stress and pin dislocations. Lower average internal stress leads to higher damping capacity of the alloy. The substitution of 0.5Mo for 0.5Al decreases the interactions between the dislocations and the solute atoms while increases the elastic distortions of the crystalline lattice, resulting in the enhancement of both strength and damping capacity.

An equiaxed grained as-cast strip and a columnar grained as-cast strip was produced by using twin-roll strip casting, respectively. Both as-cast strips mainly containing 0.71 wt%Si and 0.44 wt%Al were cold rolled and annealed with or without the hot rolling prior to cold rolling. Microstructure, texture evolution along the whole processing routes and the magnetic properties were investigated in detail. It was found that the equiaxed grained strip was characterized by almost random texture while the columnar grained strip was dominated by strong λ-fiber ( ‖ND) texture. After cold rolling and annealing, all the final sheets of both the as-cast strips showed extremely weak γ-fiber ( ‖ND) recrystallization texture. In addition, the finally annealed sheets of the equiaxed grained strip were dominated by relatively weak λ-fiber and strong Goss ({110} ) recrystallization texture while those of the columnar grained strip were dominated by much stronger λ-fiber and much weaker Goss recrystallization texture regardless of whether the hot rolling was adopted before cold rolling, thus the former showed much lower magnetic induction than the latter. On the other hand, even though the finally annealed sheets of the equiaxed grained strip showed a little more homogeneous recrystallization microstructure with a little bigger grain size than those of the columnar grained strip in the case of no hot rolling, a much higher iron loss was displayed. By contrast, in the case of hot rolling, the former exhibited a little lower iron loss than the latter as a result of the more significant increase in grain size and λ-fiber recrystallization texture. The introduction of the hot rolling could increase the grain size, strengthen λ-fiber texture and weaken Goss texture of the finally annealed sheets of both the as-cast strips, leading to a much improvement in both the magnetic induction and iron loss.

The microstructure and texture evolution of the as-cast and hot rolled grain-oriented silicon steel strips was investigated, and the precipitation of the inhibitors of the hot rolled strips was clarified. The results showed that the microstructure of the as-cast strip was characterized by coarse columnar grains with strong {001} fiber texture. The microstructure of hot rolled strips was composed of ferrite and pearlite and the microstructure was gradually refined with increasing hot rolling reduction. In the hot rolled strips, α and γ fiber textures were enhanced at the expense of initial {001} fiber texture and Goss texture was generated in the surface and sub-surface layer with increasing hot rolling reduction. Besides, a great number of dispersed MnS particles with the size of 20-30nm were observed in the hot rolled strips. These MnS particles could act as the effective inhibitors during the second recrystallization annealing of the grain-oriented silicon steel.

Low silicon non-oriented electrical steel is produced using a novel strip casting processing route. The focus is on investigating the effects of coiling temperature after hot rolling on microstructure, texture evolution, and magnetic properties. A fine microstructure with weak λ-fiber texture is formed after coiling at 650 °C. By contrast, a much coarser microstructure with a much stronger λ-fiber texture is produced after coiling at 750 °C. After cold rolling and annealing, a fine and inhomogeneous recrystallization microstructure dominated by mild λ-fiber, α-fiber, and γ-fiber recrystallization texture is formed in the case of coiling at 650 °C. By contrast, a coarse and inhomogeneous recrystallization microstructure characterized by strong Goss, α-fiber, and weak λ-fiber together with extremely weak γ-fiber recrystallization texture is formed in the case of coiling at 750 °C. Much lower iron loss and higher magnetic induction are obtained in the latter case as a result of the more desirable recrystallization microstructure and texture. It underscores that the relatively higher temperature of coiling has a similar effect as the conventional hot-band normalizing. Hence, the hot-band normalizing might be omitted in the fabrication of high-performance non-oriented electrical steels using this novel and compact strip casting production route.

Fe–6.5 wt% Si alloy doped with cerium is fabricated by twin-roll casting. Ce 2 O 2 S precipitates in the melt and acts as the efficient nucleation agent, leading to a refined solidification microstructure. The tensile ductility of this as-cast strip significantly reaches up to 56.8% at 600 °C, which is superior to the 22.8% of the as-cast strip undoped with cerium. The much more uniform and finer solidification microstructure along with the strengthened grain boundary is inferred to result in the dramatic improvement in tensile ductility.

A 0.27 mm-thick grain-oriented silicon steel sheet with extra-low carbon was successfully produced by a novel processing route including strip casting, normalizing, two-stage cold rolling with an intermediate annealing, primary annealing, and secondary recrystallization annealing. The evolutions of microstructure and texture along the whole processing route were investigated with a special emphasis on the effects of two-stage cold rolling schedule. It was found that Goss orientation originated in the first cold rolling due to shear banding and relatively strong Goss texture evolved through the whole thickness after intermediate annealing. This is significantly different from the results in conventional process in which the origin of Goss texture is in the hot rolling stage and Goss texture only develops below the sheet surface. Besides, it was found that cold rolling schedule had significant influences on microstructure homogeneity, evolution of λ-fiber texture in primary annealed state and, thus, on secondary recrystallization. In case of appropriate cold rolling schedule, a homogeneous microstructure with Goss texture, relatively strong γ-fiber texture and medium α-fiber texture was observed in the primary annealed strip. Although Goss texture in primary annealed state was much weaker than that in two-stage route in conventional process, a perfect secondary recrystallization microstructure was produced and the magnetic induction B8 was as high as 1.85 T. By contrast, when the cold rolling schedule was inappropriate, the primary annealed strips exhibited inhomogeneous microstructure, together with weak γ-fiber texture, medium α-fiber and λ-fiber texture. Finally, the sheets showed incomplete secondary recrystallization microstructure in which a large number of fine grains still existed.

Thin sheets of 6.5 wt.% Si electrical steel with the thickness of 0.35 mm were fabricated by strip casting and rolling. Influences of different cooling processes after annealing, including air cooling, water quenching, brine quenching and brine ice quenching, on the bending behavior at room temperature were systematically investigated. The results showed that with increase of the cooling rate, the room-temperature bending properties could be much improved, the fracture deflection values of the air cooled, water quenched, brine quenched and brine ice quenched specimens were measured to be 2.82 mm, 3.36 mm, 4.17 mm and 5.85 mm, respectively, moreover, obvious plastic deformation could be observed in the brine ice quenched specimen. The fracture modes of the air cooled and water quenched specimens were trans-granular cleavage fracture, while for the brine and brine ice quenched specimens, because the phosphorus segregation at grain boundary during high temperature could be preserved to room temperature by rapid quenching, the fracture modes were inter-granular fracture. The ordered phases in all specimens were observed and analyzed by TEM. The average sizes of B2 ordered domains in the air cooled, water quenched, brine quenched and brine ice quenched specimens were measured to be 107 nm, 2.7 nm, 1.6 nm, and 1.2 nm, respectively, and the DO 3 ordered domain with the average size of 2 nm could only be detected in the air cooled specimen. Therefore, the reduction of the order degree caused by fast cooling was believed to be mainly responsible for the improvement of bending properties, which might have led to significant decrease of the order-strengthening effect.

Monolithic ZrB2, ZrB2SiC, ZrB2ZrC and ZrB2SiCZrC were prepared by hot pressing in ternary ZrB2SiCZrC system. They exhibited different microstructural features. Grain sizes of each phase were smaller in the ternary composites. Contour maps of mechanical properties were also plotted in ZrB2SiCZrC ternary diagram based on experiments and software fitting. They established the relationships between chemical composition and properties in a visual way. Young’s Modulus and Vickers hardness had linear relationships with composition, while the evolution of the strength and toughness was complicated.

Fe-6.5 wt% Si non-oriented electrical steel sheets with a thickness of 0.50 mm were produced by using a new processing route: strip casting followed by hot rolling, intermediate temperature (150–850 °C) rolling and final annealing. The present study focused on exploring the effects of rolling temperature varying from 150 to 850 °C on the microstructure and texture evolution, the formability and final magnetic properties. The microstructure and texture evolution at the various processing steps were investigated in detail by using OM, XRD, EBSD and TEM. It was found that the formability during rolling, the microstructure and texture before and after annealing and final magnetic properties highly depended on rolling temperature. The formability during rolling was gradually improved with increasing rolling temperature due to the slipping of dislocation. In particular, the rolling temperature dominated the formation of in-grain shear bands in the rolled microstructure, which played an important role in the development of final recrystallization microstructure and texture. In the case of lower temperature (150–450 °C) rolling, an inhomogeneous microstructure with a large amount of in-grain shear bands was formed in the rolled sheets, which finally resulted in a fine and inhomogeneous annealing microstructure dominated by mild λ-fiber texture composed of cube and {001}〈210〉 components and α*-fiber texture concentrated on {115}〈5–10 1〉 component. By contrast, in the case of higher temperature (650–850 °C) rolling, a relatively homogeneous microstructure without in-grain shear bands was formed instead in the rolled sheets, which finally led to a coarse and relatively homogeneous annealing microstructure characterized by strong α-fiber and γ-fiber texture. Accordingly, on the whole, both the magnetic induction (B 8 and B 50 ) and iron loss (P 15/50 and P 10/400 ) decreased with raising rolling temperature.

Herein, four kinds of initial Goss textures with different deviation angles (0°, 5°, 10°, and 15°) are obtained by controlling the included angles between the longitudinal directions of rectangular cutting specimens and the initial rolling direction of the raw material. Then, 0.05 mm thick grain‐oriented silicon steels are fabricated by cold rolling and primary recrystallization annealing. Effects of initial textures on the microstructure and texture evolutions and magnetic properties are investigated in detail. Compared with sharp {111} in the cold rolling sheet with initial exact Goss, the deviated Goss favors the formation of strong {111} + weak {h11} textures. After annealing, sharp {210} + medium {110} textures develop as a result of the small initial deviation, while larger initial deviations contribute to the {310} texture. In addition, the average grain sizes are also related to recrystallization textures. Consequently, the distinct recrystallization microstructures and textures result in the differences of magnetic properties.