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Hot rolling is one of the key processes in the new casting–rolling forming process of high‐silicon electrical steel. The hot deformation characteristics, microstructure, and defects after deformation strongly influence the formability in subsequent warm‐ and cold‐rolling processes. This study investigates the hot compression behavior of Fe–6.5 wt% Si–0.15wt%Nb and Fe–6.5 wt% Si samples at 800–1100 °C as well as the effect of Nb on the flow stress, dynamic recrystallization, and ordered structure of high‐silicon electrical steel. The results show that the grain size of the Nb‐containing as‐cast samples is small. The Nb‐rich second‐phase particles can inhibit the growth of dynamic recrystallization grains during hot compression and refine the dynamic recrystallization microstructure; consequently, the hot activation energy of Nb‐containing samples is 11.8% higher than that of Nb‐free samples. Microcracks appear in the Nb‐free samples at temperatures of 800 and 1100 °C and strain rates of 1 and 10 s−1; the addition of Nb can effectively inhibit the generation of microcracks during hot deformation. The addition of Nb reduces the ordered degree of high‐silicon electrical steel after hot compression, which is beneficial to the subsequent warm‐ and cold‐rolling processes. [ABSTRACT FROM AUTHOR]

A thin oxide film on NZ alloy (Zr-1Sn-0.3Nb-0.3Fe-0.1Cr) was formed to investigate the correlation of microstructure and corrosion behavior at the initial stage by directly identifying defect-enriched sites. The sites of high conductivity are revealed and labelled by silver deposition, and in the further investigation of microstructure secondary phase precipitates (SPPs) interconnected with micro cracks are found below. Enrichment of oxygen-18 and deuterium in SPPs after isotopic tracing by secondary corrosion highlights their influence on carrier diffusion. Thus, the percolation for corrosion media transportation is reached locally by SPPs interconnected with micro cracks. • New method of silver deposition to pinpoint the permeable sites of the oxide film for carrier diffusion. • Discovery of oxygen and hydrogen enriched in SPPs after isotope tracing. • SPPs bridge micro cracks as the preferential pathways of corrosion. [ABSTRACT FROM AUTHOR]

The effect of hot deformation parameters on microstructure coarsening of the medium‐carbon microalloyed steel is studied by means of hot compression experiments. The effective strain of finish forging in a crankshaft is simulated by means of finite element numerical simulations. The microstructure and properties of the crankshaft are also analyzed. The hot compression experiments result shows that with the deformation increasing from 2% to 18%, the austenite grain size first increases and then decreases, and it reaches the maximum when the deformation is 6%. The microstructure coarsening is mainly caused by critical deformation. With the increase in deformation temperature and the decrease in strain rate, the austenite grains can also be coarsened. When the effective strain of finish forging exceeds 0.2 in the main journal section of the crankshaft, the microstructure is refined significantly, and mechanical properties are improved. To avoid coarse microstructure, the reduction of finish forging should reach 15–20 mm. [ABSTRACT FROM AUTHOR]

Abstract The present work investigated the effect of the addition of V 2 O 5 and MnCO 3 on the microstructure and magnetic properties of Ni-Zn ferrite ceramic samples prepared by a conventional ceramic sintering method at different temperatures. With this aim, a series of samples were prepared by varying the loadings of V 2 O 5 -MnCO 3 (un-doped, 0.4–0.1 wt%, 0.1–0.4 wt%, 0.2–0.3 wt%, 0.3–0.2 wt%, and 0.5–0.1 wt%, denoted as sample 1, sample 2, sample 3, sample 4, sample 5, and sample 6, respectively). The initial permeability and power loss of the different Ni-Zn ferrites were investigated with respect to the sintering temperature. The V 2 O 5 and MnCO 3 dopants significantly improved the initial permeability and power loss characteristics of the Ni-Zn ferrite at frequencies ≥0.5 MHz. When sintered at 1100 °C, sample 2 showed a maximum initial permeability of 931.23 H/m at a frequency of 1 MHz combined with a minimum power loss of 339.2 kW/m3. Co-doping with V 2 O 5 and MnCO 3 also resulted in the sintered samples with larger average grain sizes and higher density, while the sintering temperature of Ni-Zn ferrites was significantly reduced. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The uneven B distribution promoted the formation of intragranular ferrite idiomorphs. • The formation of BN leaded to B-depletion near the MnS inclusion. • The experimental results can be widely used in the ferrite-pearlite forging steels. Abstract The microstructure and properties of a V-Ti microalloyed forging steel was optimized by boron addition. The uneven distribution of boron suppressed the formation of grain boundary ferrite (GBF) and promoted the formation of intragranular ferrite (IGF) idiomorphs. The volume fraction of GBF decreases from 21.2% to 14.3%, while that of IGF idiomorphs increases from 3.5% to 10.2%. After boron addition, the strength of the steel has little change, but the total elongation increases from 21.2% to 23.6%, and the impact energy increases from 38.2 J to 51.4 J, which is attributed to the higher volume fraction of IGF idiomorphs. [ABSTRACT FROM AUTHOR]

Abstract The toughening mechanisms of microstructural variation and Ni addition were investigated in two direct-cooled microalloyed ferrite-pearlite steels by using the U-notched Charpy tests. Results show that the impact toughness of the low Ni steel decreases dramatically from 110 J to 20 J when the prior austenite grain size increases from 10 µm to 37 µm, and then stays unchanged as the prior austenite grain size continues increasing from 37 µm to 90 µm. When the prior austenite grains are finer than 37 µm, the cleavage fracture is much postponed and the area of ductile fracture is much enlarged by the significantly improved ability to perform plastic deformation. When the prior austenite grains are coarse, the energy absorbed by cleavage, which is the main mode of fracture, conforms to the Griffith type equation and is much less compared to that consumed by ductile fracture, leading to the low impact toughness. The cumulative effect of ferrite content and pearlite interlamellar spacing on impact toughness is not obvious, because their influences are contradictory as the cooling rate is raised. There is a steady enhancement of about 20 J in impact toughness of the high Ni steel compared to the low Ni steel, when the austenite grain size exceeds about 37 µm. The area of ductile fracture is enlarged by the increased dislocation mobility in high Ni steel, resulting in the improvement of impact toughness. It is difficult to refine the prior austenite grain size to less than 37 µm of microalloyed ferrite-pearlite steels through optimizing forging and cooling process. However, small amount of Ni addition is beneficial to the impact toughness and does not increase the cost significantly. [ABSTRACT FROM AUTHOR]

The size and thermal stability of Manganese Sulfide (MnS) inclusions in two low cost hot forged steels with no microalloying elements are carefully investigated. Based on the results, the austenite grain growth behavior of the two steels are studied and the effect of MnS inclusions on the austenite grain growth are discussed using an optical microscope, a scanning electron microscopy, and a confocal scanning laser microscopy. Results show that the MnS inclusions hold a favorable thermal stability and do not dissolve in the steel heated at 1250 °C for 30 min. Austenite grains of the steel with larger quantities of smaller size of MnS inclusions are significantly finer than that of the steel with less and larger size of MnS inclusions heated at a temperature above 1000 °C. The differences in grain size become greater, as the heating temperature increases. The pinning effect of MnS inclusions plays an important role during austenite grain growth, when the austenite grain size exceeds the average spacing of MnS inclusions. The results indicate that large quantities of small MnS inclusions can be used to inhibit austenite grain growth during heating process in a low cost hot forged steel, where expensive microalloying elements are removed. [ABSTRACT FROM AUTHOR]

NaNbO 3 (NN) ceramics are promising candidate materials for capacitors, where dielectric properties are crucial for application in complex circumstances. However, conventional sintering requires several hours for the sintering process, which is not only inefficient but also results in significant energy consumption. In this study, NN ceramics with a relative density of 95% and smaller grain size were obtained using an ultrafast high-temperature sintering (UHS) at 1100 °C for 60 s. The dielectric constant of NN ceramics at 1 KHz keeps at 1460.52, with a low dielectric loss. And UHS technique refines the grains and prevents the volatilization of Na for a very short time, which is because it bypasses the necking stage and effectively prevents grain coarsening. This novel technique provides a simple and efficient technical support to obtain dielectric materials. [ABSTRACT FROM AUTHOR]

• This paper clarifies the effect of billet microstructure and deformation on austenite grain growth in forging heating. • This paper provides important guidance for rolling process of medium-carbon microalloyed steel billets for hot forging. • This paper provides a new insight into the control and prediction of austenite grain growth. [Display omitted] We prepared samples with different ferrite-pearlite characteristics and deformation by heat treatment and Gleeble thermocompression respectively. Then, the different samples are rapidly heated to 1200 °C for 60 s to study the austenite grain growth. The study results show that the ferrite-pearlite characteristics has little effect on austenite grain growth. With the mean austenite grain size (MAGS) of billet microstructure increasing from 14 µm to 56 µm, the MAGS after heating only increases from 47 µm to 56 µm. With the cooling rate of billet samples increasing from 0.1 °C/s to 1.0 °C/s, the MAGS after heating has basically no change. However, the deformation of billet samples has significant effect on the austenite grain growth. With the deformation at 1150 °C increasing from 10% to 50%, the MAGS after heating decreases from 63 µm to 31 µm. In the meanwhile, the mean distance between element segregation bands decreases from 115 µm to 33 µm, and the mean width of element segregation bands decreases from 70 µm to 20 µm. Electron probe microanalysis shows that the segregation region has higher Si, Cr, Mn and V contents, which generate stronger solute drag effect on austenite grain boundaries. Deformation can crush the as-cast grains and make the segregation bands fine and dispersed, further refining the austenite grains after heating. [ABSTRACT FROM AUTHOR]

In this paper, the effects of Nb contents (0.05 ~ 0.50wt%) and hot rolling temperatures (1000 ~ 1200 °C) on microstructure and mechanical properties of high-silicon electrical steel were studied. The results show that adding a small amount of Nb can significantly improve the plasticity of high-silicon electrical steel. Compared with the specimens without Nb, the three-point bending load–deflection curves of the alloys with Nb contents of 0.05 ~ 0.50wt% after warm rolling showed obvious plastic stage. The average fracture deflection increases from 4.5 to 9.9 mm with the Nb content increasing from 0.05 to 0.50wt%. When the hot rolling temperature is 1000 °C, the Nb-containing high-silicon electrical steel has a layered microstructure along the thickness direction. The surface layer is equiaxed grains with dynamic recrystallization, while the center of the thickness is a long strip structure with dynamic recovery. The mechanism of Nb microalloying to improve plasticity includes three aspects: Firstly, the layered structure hinders the propagation of cracks and delays the progress of fracture; secondly, a large number of fine Nb precipitates will hinder the grain growth and refine the grains; thirdly, the formation of the Nb-precipitated phase destroys the ordered rearrangement between adjacent Fe and Si atoms in the matrix, inhibits the ordered transformation and reduces the ordered degree of high-silicon electrical steel. When the hot rolling temperature is increased to 1100 °C or above, the layered structure disappears, the grain coarsens obviously, and the plasticity of the warm-rolled specimens is significantly reduced. [ABSTRACT FROM AUTHOR]

• Magnetic properties can be controlled by adjusting annealing temperature. • The precipitated phase of Nb can provide remarkable fine-grain effect. • The {1 1 1} texture weakened and the {1 0 0} and {1 1 0} texture enhanced by increasing annealing temperature. • The experimental results can be widely used to control the microstructure and properties of high silicon electrical steel. Fe-6.5 wt% Si alloy (high silicon electrical steel) is an ideal core material for making motors and transformers with low noise and low power loss. Controlling microstructure and texture is key to improving the magnetic properties of high silicon electrical steel. In order to improve the warm rolling and cold rolling workability of high silicon electrical steel, in this paper, 0.03 wt% Nb is added to the alloy, and a strip sample with a thickness of 0.13 mm was prepared. The effect of annealing temperature on microstructure, texture and magnetic properties of the samples was studied. The results show that annealing at 800 ℃–1300 ℃ for 1 h, with the increase of annealing temperature, the {1 0 0} texture content of the sample decreased from 9.47% to 1.09%, {1 1 0} texture content gradually increased from 1.26% to 33.1%, {1 0 0}+{1 1 0} texture content increased significantly from 10.73% to 34.19%. Nb-rich precipitates are formed in high silicon electrical steel with a size of about 100 nm. When the annealing temperature is lower than 1200 ℃, the Nb-rich precipitates can inhibit the grain growth. When the annealing temperature is higher than 1200℃, the Nb-rich precipitates dissolves and the pinning force to the grain boundary is weakened. The 0.13 mm Nb-microalloyed high silicon electrical steel strip has good magnetic properties at 800–1300 °C for 1 h. At 1200 °C, the grain growth and iron loss decrease due to the dissolution of the Nb-rich precipitates, so that the sample has a high comprehensive magnetic property: B 8 is 1.31 T, B 50 is 1.61 T, and P 10/50 is 0.411 W/kg, P 10/400 is 5.416 W/kg. [ABSTRACT FROM AUTHOR]

TiAlSiN coatings with different Si contents (1.84–4.81 at.%) were prepared on WC-Co substrates by plasma immersion ion implantation and deposition using different TiAlSi cathodes. (Ti, Al)N (200), (220) and (311) diffraction peaks could be found in X-ray diffraction (XRD) patterns of the as-deposited coatings and a preferred orientation (Ti, Al)N (200) was obvious for all samples. X-ray photoelectron spectroscopy (XPS) results showed the existence of TiN, AlN, TiO x N y and SiN x. High resolution transmission electron microscopy (HRTEM) images exhibited that the microstructure of TiAlSiN coating was gradually changed from poly-nanocrystalline to (200) preferred oriented (Ti, Al)N embedded in an amorphous matrix. Nanoindentation results revealed that all the coatings exhibited high hardness, where the maximum value reached 45.3 GPa at a silicon content of 3.43 at.%. Scratch tests were performed on these samples, and the highest critical load (L C4) of the coatings reached 158.4 N, indicating that good adhesive strength was obtained by this deposition method. • TiAlSiN ultra-hard coating (45.3 GPa) was prepared by PIIID with a single TiAlSi alloy cathode. • The adhesive strength of the TiAlSiN coating reached 158.4 N, which is the highest among the published works. • The variation of the microstructure along the growth direction of the TiAlSiN coating was identified. [ABSTRACT FROM AUTHOR]

The second phase in the alloy powder prepared by close coupled argon atomization was submicron and nanometer scale, and distributed in the copper matrix uniformly. The strengthening effect could be increased evidently. • The Cu-2Cr-1Nb alloy powder was prepared by close-coupled argon gas atomization. • The Cr 2 Nb precipitate is submicron and nanometer, which distributed uniformly. • Heat treatment can regulate the alloy powders' microstructure and microhardness. • The powder (26–50 μm) has similar microhardness with extruded Cu-8Cr-4Nb alloy. • This method can be used to prepare the excellent powder for Cu-Cr-Nb alloy. The Cu-2Cr-1Nb (at%) alloy powder was prepared by close-coupled argon gas atomization. The morphology, microstructure and phase were characterized by SEM, TEM, HRTEM, SAED and XRD. The effects of heat treatment on the microstructure and microhardness of the powder were investigated. The alloy matrix had equiaxed crystal structure, and the second phase was Cr 2 Nb intermetallic compound in sub-micron and nano-scale. Compared with large powder, the second phase of small powder is finer, and its distribution in the matrix is more uniform, the microhardness of the small powder is higher. After heat treatment at 773 K for 1 h, Cr and Nb precipitated and formed a large number of small precipitates, age hardening and peak aging phenomena occurred, and the peak hardness of the powder reached 130 HV. With the increase of heat treatment temperature, the second phase was coarsened. When the heat treatment temperature was 973 K, the short-time heat treatment hardening and long-time heat treatment softening were shown. However, after the heat treatment at 1223 K, only softening phenomenon was observed. This method can be used to prepare the excellent powder for Cu-Cr-Nb alloy, which can be used as a potential structural material for aerospace. [ABSTRACT FROM AUTHOR]