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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]

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]

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]