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This study explores the evolution of solidification microstructure of a laser powder bed fusion (L-PBF) martensitic stainless steel during solution annealing and aging. Quasi in-situ experiments using electron backscatter diffraction (EBSD) revealed that the finer, more equiaxed microstructure below the melt pool was susceptible to recrystallization and grain growth during solution annealing. The two distinct solidification microstructures below and inside the melt pool converged into a uniform grain morphology after solution annealing and aging processes. [ABSTRACT FROM AUTHOR]

This research aims to fabricate hydrophobic electrospun air filters with ultra-high performance against virions. In order to achieve this goal, constant basis weight electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) with low-bead, high-bead, and ultra-high-bead fibre structures were used to fabricate single and multilayer filters by controlling the Dimethylformamide (DMF)-to-acetone ratio of the solvent. The water contact angle of the fabricated layers ranged from 131° for low-bead structures to 135° for ultra-high-bead structures, indicating their overall high hydrophobicity. The size-resolved filtering efficiency and pressure drop tests on the fabricated filters showed that low-bead structure for both single and multilayer filters and high-bead structure for single-layer filters enhance the quality factor remarkably. The results showed that the single-layer ultra-high-bead structure air filters had a filtering efficiency of 99.33%, superior to N95 air filters (96.54%) and comparable to double N95 filters (99.86%). However, the electrospun air filter showed a pressure drop of 169.3 Pa and a quality factor of 27.6 × 10 − 3   P a − 1 compared to a pressure drop of 388 Pa and quality factor of 16.9 × 10 − 3   P a − 1 for double N95 air filters. Therefore, it has a high potential to be used as the filtration media in hospitals, long-term care centers, and masks to provide superior protection against virions for healthcare providers and patients. [ABSTRACT FROM AUTHOR]

This research focused on the corrosion resistance and microstructure of hybrid additively manufactured (HAM) samples of AISI 420/CX (420/CX SS) stainless steels. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott–Schottky analyses as well as the electrochemical noise (EN) technique were used to evaluate the electrochemical behavior of the as-built and heat-treated HAM parts in NaCl solution. The results showed a more protective passive layer formed on the CX SS side. The distribution of Cr-rich M23C6 carbides in matrix of 420 SS side resulted in a lower corrosion resistance compared to the CX SS side. The noise data analysis confirmed an increase in the galvanic currents of the HAM parts after heat treatment. The stochastic analysis revealed the interface in the heat-treated condition increases pit growth more than the as-built one due to the evolution of nano-sized intermetallic compounds of Al-N/ (Cr, Nb) (N, C) at the heat-treated interface area. [ABSTRACT FROM AUTHOR]

This research focused on the corrosion resistance and microstructure of hybrid additively manufactured (HAM) samples of AISI 420/CX (420/CX SS) stainless steels. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott–Schottky analyses as well as the electrochemical noise (EN) technique were used to evaluate the electrochemical behavior of the as-built and heat-treated HAM parts in NaCl solution. The results showed a more protective passive layer formed on the CX SS side. The distribution of Cr-rich M23C6 carbides in matrix of 420 SS side resulted in a lower corrosion resistance compared to the CX SS side. The noise data analysis confirmed an increase in the galvanic currents of the HAM parts after heat treatment. The stochastic analysis revealed the interface in the heat-treated condition increases pit growth more than the as-built one due to the evolution of nano-sized intermetallic compounds of Al-N/ (Cr, Nb) (N, C) at the heat-treated interface area. [ABSTRACT FROM AUTHOR]

In this work, the effect of heating rate on the phase transformation temperatures was investigated using dilatometry analysis. Continuous heating and isothermal holding above Ac3 temperature on microstructural evolutions in additively manufactured (AM) parts of Fe-Cr-Ni maraging stainless steel were studied. The microstructural features developed within the heating processes were characterized employing electron backscatter diffraction and transmission electron microscopy. Austenite reversion was found to take place in two steps for the AM parts by a diffusive mechanism as well as the precipitation reactions. Although grain refinement occurred during the austenite reversion of the continuously heated samples, the microstructure showed a coarser grain size after isothermal heating. The crystallographic orientations developed after the heating processes were different from those of the initial ones implying the absence of the austenite memory effect. [ABSTRACT FROM AUTHOR]

Characterization of the austenite phase at high temperatures is important for understanding the microstructural evolution during steel processing. The austenite phase structure can be reconstructed from the room‐temperature microstructure employing the crystallographic orientation relationship between the parent and product phases. The actual orientation relationships in steels are often calculated on the basis of well known relations (e.g. Kurdjumov–Sachs), which may differ from the experimentally observed orientation relationships. This work introduces a new approach to improve the current state of the art in prior phase reconstruction. The proposed approach consists of two new algorithms that are sequentially applied on an electron backscatter diffraction (EBSD) measured data set of the product phase microstructure: (i) an automated identification of the optimum orientation relationship using the observed misorientation distribution of the entire EBSD scan and (ii) reconstruction of the parent phase microstructure using a random walk clustering technique. The latter identifies groups of closely related grains according to their angular deviation from the proposed orientation relationship. The results were validated by near in situ experimental observations of phase transformation in an Fe–Ni alloy whereby the experimentally measured parent phase structure could be compared point by point with the reconstructed counterpart. [ABSTRACT FROM AUTHOR]

Due to high local cooling rates and non-equilibrium directional solidification conditions, selective laser melting (SLM) processed metals exhibit microstructural and textural features significantly different from the conventionally processed ones. The evolution of crystallographic orientations in a maraging stainless steel (commercially known as stainless steel CX) sample fabricated by the SLM process was studied through experimental and modelling approaches Electron backscattering diffraction analysis showed that the dominant texture components in martensite and austenite phases are <111>|| building direction and <011>|| building direction, respectively. Texture simulation indicated that the formation of crystallographic orientations in the studied sample is the result of two consecutive phase transformations, from initially solidified delta ferrite phase with dominant cube fiber texture to austenite and austenite to martensite. [ABSTRACT FROM AUTHOR]

The evolution of microtexture and microstructure of a cross-rolled 0.88 wt pct Si non-oriented electrical steel was investigated using a quasi- in situ electron backscatter diffraction (EBSD) technique, where individual deformed grains with various initial orientations were tracked during annealing at the same temperature for different times. The textures recrystallized from different deformed grains were compared, and the observations were examined against the preferential nucleation and selective growth theories. Although the cold deformed 〈111〉//ND (normal direction) grains recrystallized first during annealing, they started with significantly different nucleation textures, i.e., γ-fiber (〈111〉//ND) in {111}〈112〉 deformed grains, and cube ({001}〈100〉) in {111}〈110〉 deformed grains. Both recrystallization textures were quite stable until the steel was completely recrystallized. Significant grain growth in these grains was only observed after the recrystallization was complete, which resulted in considerably different final textures as compared to the initial nucleation textures. Deformed grains with a rotated cube ({001}〈111〉) orientation were the last to recrystallize, and the recrystallization was accomplished mainly through the 'invading' of neighboring grains into the deformed matrix. Analysis of the misorientations between the rotated cube grain (the matrix) and their neighboring recrystallized grains showed that the preferred growth of some of the grains can be attributed to the high grain boundary mobility associated with the coincident site lattices (CSL). During the course of recrystallization, some $$ \{ 11{\text{h}}\} \left\langle {12\frac{1}{h}} \right\rangle $$ and rotated cube grains also formed, but they disappeared quickly when the annealing time was increased. [ABSTRACT FROM AUTHOR]

A novel rolling technique, i.e., skew rolling, was applied to a non-oriented electrical steel containing 0.9 wt% Si, aiming at altering the texture of the final sheets that usually contain the magnetically unfavorable <111>//ND fiber after conventional rolling and annealing. The texture after skew cold rolling was compared to those obtained from conventional rolling and cross rolling and significantly different textures were observed. The cold-rolled steel sheets were then annealed and the texture evolution was investigated using a quasi in situ electron backscatter diffraction technique, i.e., tracking the microtexture of the same area at various holding times at the same temperature. The development of the recrystallization microstructure and microtexture (nucleation and grain growth) was characterized and the effect of skew rolling on the final texture was studied. The mechanisms governing the formation of the final recrystallization texture, e.g., preferential nucleation and selective growth, were elucidated. [ABSTRACT FROM AUTHOR]

In this study, effects of dynamically formed precipitates on the microstructure and texture evolution were investigated during the post-deformation annealing. Two ternary alloys of Mg, Al, and Sn were produced and deformed at 250 and 300 °C to form different amounts of strain-induced precipitates during deformation and different levels of dynamic recrystallization. Subsequent annealing at deformation temperatures was performed at various times for up to 4 h and recrystallization, grain coarsening, and precipitation behaviors were characterized. The deformed structures were all partially dynamically recrystallized exhibiting necklacing. Static recrystallization (SRX) progressed by the transformation of the coarse grained un-necklaced regions to fine grains. It was found that increasing levels of pre-existing precipitates on dynamic recrystallized grain boundaries inhibited SRX as well as grain coarsening, by precipitation pinning. Texture was weakened after a short time annealing compared to the as-deformed condition and high amount of precipitates at the grain boundary restricted the grain coarsening and kept the texture weaken associated with grain coarsening. [ABSTRACT FROM AUTHOR]

The final mechanical properties of wrought magnesium alloys are mostly controlled by its microstructure and crystallographic orientation or texture. In the sheet form of common magnesium alloys, grain coarsening occurs during annealing, which only serves to strengthen the undesirable basal texture. One method to alleviate this problem is by stopping grain coarsening. Hence the aim of this work is to investigate the effect of static precipitation on microstructure and texture evolution during annealing at various temperatures after cold rolling. Mg-Al-Sn alloys were designed using thermodynamic modeling software, FactSage. It was found that static precipitates can only form extensively, after static recrystallization, at the recrystallized grain boundaries, and these retard grain growth during annealing. Presence of precipitates at the recrystallized grain boundaries also retard the strengthening of basal texture during annealing, related to grain coarsening. [ABSTRACT FROM AUTHOR]

The fabrication of Polyvinylpyrrolidone (PVP) electrospun layers for air filter applications is the target of this study. Solutions of 10% PVP containing 0, 3, 10 and 25 wt% nanoclay were used to fabricate electrospun fibers. Scanning electron microscopy showed that the fibers' roughness increased by increasing the nanoclay content, and it was maximum at the nanoclay concentration of 25 wt%. Concurrently, nanoclay decreased the pore size considerably and increased the range of the fibers' size distribution up to 100%. In addition, as the nanoclay concentration increased, the frequency distribution decreased abruptly for the larger fiber sizes and increased dramatically for the small fiber sizes. This phenomenon was correlated to the effect of nanoclay concentration on the conductivity of the solution. The solution's conductivity increased from 1.7 ± 0.05 µS/cm for the PVP solution without nanoclay to 62.7 ± 0.19 µS/cm for the solution containing 25 wt% nanoclay and destabilized the electrospun jet, increasing the range of fiber size distribution. Therefore, the PVP solution containing 25 wt% nanoclay has potential characteristics suitable for air-filter applications, owing to its rougher fibers and combination of fine and thicker fibers. [ABSTRACT FROM AUTHOR]

The high photocatalytic power of TiO2 nanoparticles has drawn great attention in environmental and medical applications. Coating surfaces with these particles enables us to benefit from self-cleaning properties and decomposition of pollutants. In this paper, two strategies have been introduced to coat ceramic tiles with TiO2 nanoparticles, and the self-cleaning effect of the surfaces on degradation of an organic dye under ultraviolent (UV) exposure is investigated. In the first approach, a simple one-step heat treatment method is introduced for coating, and different parameters of the heat treatment process are examined. In the second method, TiO2 nanoparticles are first aminosilanized using (3-Aminopropyl)triethoxysilane (APTES) treatment followed by their covalently attachment onto CO2 plasma treated ceramic tiles via N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) and N-Hydroxysuccinimide (NHS) chemistry. We monitor TiO2 nanoparticle sizes throughout the coating process using dynamic light scattering (DLS) and characterize developed surfaces using X-ray photoelectron spectroscopy (XPS). Moreover, hydrophilicity of the coated surfaces is quantified using a contact angle measurement. It is shown that applying a one-step heat treatment process with the optimum temperature of 200 °C for 5 h results in successful coating of nanoparticles and rapid degradation of dye in a short time. In the second strategy, the APTES treatment creates a stable covalent coating, while the photocatalytic capability of the particles is preserved. The results show that coated ceramic tiles are capable of fully degrading the added dyes under UV exposure in less than 24 h. [ABSTRACT FROM AUTHOR]