Materials Science Forum Vol. 1137

Abstract: Polyethersulfone membranes were fabricated using non-solvent-induced phase separation (NIPS) with silica and nanocellulose additives extracted from rice husk ash and genjer (Limnocharis flava). N-methyl pyrrolidone served as the solvent. The study aimed to prepare membranes with diverse characteristics by incorporating various combinations of additives. Silica acted as a pore-forming agent, while nanocellulose enhanced membrane hydrophilicity. Characterization techniques included Fourier-transform infrared spectroscopy (FTIR) for functional group analysis, which revealed the presence of C-S, Si-O, and Si-O-Si vibrations in the membranes. Additionally, scanning electron microscopy (SEM) was employed to examine the surface and cross-sectional structure of the membranes. To assess membrane performance, a flux test was conducted. The membrane containing 2% nanocellulose and 1% silica exhibited the highest flux value of 21.37 L/m².h, corresponding to a permeability of 21.37 L/m².h.bar. Based on these results, the membrane with 2% nanocellulose and 1% silica is considered optimal due to its superior performance.

Abstract: Polyether sulfone (PES) stands as a widely utilized polymeric membrane in separation technology. However, due to certain undesirable drawbacks encountered in its application, researchers consistently strive to enhance its characteristics and performance. In this study, we delve into the effects of Mg(OH)₂ addition on the characteristics and performance of PES membranes employed for humic acid removal from water. The membrane fabrication involves PES as the primary polymer, NMP as the solvent, and a blend of ethanol and water as non-solvents. Characterization of the membranes encompasses the assessment of functional groups via FTIR, morphological structure through SEM imaging, and porosity evaluation. Notably, the Mg(OH)₂ additive exerted a positive influence on the prepared PES membranes, leading to discernible alterations in the morphological structure, as evident in SEM cross-sectional images. The augmentation of Mg(OH)₂ concentration resulted in increased membrane porosity. The FTIR spectra revealed the presence of water derived from Mg(OH)₂ crystals. The research yielded notable results, with the most outstanding membrane exhibiting a pure water flux of 41.6 L/m2·h and a rejection rate of 71%. Furthermore, it displayed a Water Flux Recovery Ratio (FRR) of 72%. These findings underscore the effectiveness of incorporating Mg(OH)₂ as an additive in enhancing the performance of PES membranes for humic acid removal, with promising implications for water purification applications.

Abstract: Ni-based superalloys are commonly utilized in the production of hot-end components in the aerospace, energy, and other sectors. Due to the extreme environment, phase coarsening is prone to occur within the alloys, leading to degradation in the mechanical properties and thus posing a risk to equipment safety. To investigate the influences of volume fraction of precipitation particles and phase coarsening on hardness of materials, and explore the relationship between their microstructure and macroscopic hardness, based on the finite element method simulations, a two-dimensional Vickers hardness model is constructed for testing. Results show that hardness is closely linked to the particle shape, size, and distribution features; with the increase of the volume fraction of particles or the degree of phase coarsening, the hardness of alloys gradually weakens; and when the volume fraction of particles is larger, the decrease in the hardness is more obvious along with the degree of phase coarsening. Related research makes a good reference for the design of Ni-base superalloy structures as well as the evaluation or prediction of their mechanical properties during the service.

Abstract: This study investigates the influence of α/β interface characteristics on the mechanical properties and plastic deformation behavior of titanium alloys, focusing on Ti-Al-V system. Molecular dynamics simulations of Ti-Al-V alloys with different gradient α/β interface models reveal that the linear gradient interface exhibits superior strength at ultra-low temperatures compared to "S" gradient and non-gradient models. Analysis indicates structural transitions primarily occur at the interface at 70 K. Dislocation analysis shows high strength of the linear gradient interface at 70 K and 0.01 K, with dislocations concentrated at the α/β interface. With the change of interface characteristics, the mechanical properties also exhibit gradient variations.

Abstract: Compared with traditional shielded metal arc welding and semi-automatic welding, fully automatic welding has the advantages of fast welding speed, high welding quality as well as a high qualification rate on the premise of ensuring the comprehensive performance of the girth weld joint. Meanwhile, the proportion of welding defects also changed from porosity and slag inclusion to lack of fusion. Therefore, from the view of the macroscopic and dynamic evolution behavior, the paper aims to reveal the influence of the coupling of weld-pass morphology and molten-pool flow on the formation of lack of fusion using macroscopic metallographic observation and high-speed photography. The results indicate that the weld morphology is prone to convex reinforcement and larger penetration depth in the 6 o’clock direction of the pipeline girth weld under the reference parameters. The excessive reinforcement of the pass to be welded is one of the sufficient conditions for the formation of a lack of side fusion in the 6 o’clock direction. Excessive reinforcement could lead to welding arc heat mainly used to melt the raised weld metal to be welded, which results in insufficient heat flow to both sides of the molten pool metal. Furthermore, due to the larger curvature radius at the groove and the increase of the surface tension of the molten pool with lower relative temperature, the flow resistance of the molten pool increases and the fluidity decreases.

Abstract: Fe-6.5wt%Si high silicon steel alloy was prepared using the vacuum induction melting method. Ordered phase formation in Fe-6.5wt%Si alloy was inhibited by adding trace Cu and induction cycle heating purification treatment. The microstructure and magnetic properties of high silicon steel were investigated. The results show that with the increase of Cu content, the alloy microstructure first changed from coarse grain to fine isoaxial crystal, followed by strip dendrite, with ordered cracking. The saturated polarization strength of the alloy decreased from 25.1 emu of the sample without adding Cu and heating once to 21.5 emu for seven cycles, the residual magnetic polarization increased from 0.0255 emu to 0.048 emu, the slope of the magnetization curve slowed down, and the coercive force increased from 2.4 Oe to 4.0 Oe. With the increase of cyclic heating times, the microstructure of the alloy without added Cu refined and transitioned from columnar to equiaxial crystals, from isoaxial dendrite to strip with the addition of 0.03 wt%Cu, and from strip to isoaxial structure with the addition of 0.05 wt%Cu. With the increase of cycle heating times, the saturation magnetization strength of the alloy without Cu and with 0.03 wt%Cu alloy increased, while the recalcitrant force reduced. Conversely, the saturation polarization strength decreased for the alloy with 0.05 wt% Cu, and the coercive force was also reduced.

Abstract: This study investigates the influence of Cu and La additions on the solidification structure and phase formation behavior of Fe-6.5wt%Si high silicon steel. The alloy's phase composition and structure were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The magnetic performance was measured using a high and low-temperature vibration magnetometer. The results revealed that the microstructure of the Fe-6.5wt.%Si alloy ingot, treated with Cu and La inhibitors, is segmented into three layers. From the bottom to the top, the phase morphology is fine crystals, columnar crystals, and isoaxial crystals. Adding Cu and La inhibitors significantly refined the Fe-6.5wt.%Si alloy; adding 0.05% Cu transformed thick columnar crystals into slender branches, while 0.03% La led to a uniform refinement of grains. Cu addition maintained the alloy saturation magnetization strength but increased coercivity. La addition decreased the alloy's saturation magnetization and increased coercivity.

Abstract: To measure the dynamic mechanical properties of 12X18H10T stainless steel at high strain rates, dynamic impact tests were conducted on 12X18H10T specimens at three high strain rates using the SHPB apparatus. The dynamic engineering stress-strain data and true stress-strain data of 12X18H10T stainless steel at different strain rates were obtained using the classical three-wave method theory. The engineering stress-strain data and the Cowper-Symonds constitutive model were used to fit least squares data to obtain the dynamic yield strength and strain rate-dependent parameters separately. This provides input data for the drop test simulation of shipping containers of radioactive materials considering the strain rate effect.

Abstract: This research focuses on development of infra-lightweight foamed concrete with very low density. The first step is to manufacture stable preformed foam with optimizing the applied air and water pressure as well as the foaming agent dosage. Then, an appropriate mixing procedure of infra-lightweight concrete is developed. In the experimental plan, 8 different mixes are prepared and tested with different densities, 200, 300, 500, 600 kg/m³. Two values of w/c ratio are used, 0.6 and 0.4. A superplasticizer compatible with the foaming agent is used in the second case (w/c 0.4) in order to achieve the required workability. Compressive strength, thermal conducting and scanning electron microcopy (SEM) measurements have been measured in order to characterize the developed foamed concrete. The experimental results show that for infra-lightweight foamed concrete, the material density is the main parameter governing its compressive strength and thermal conductivity. The SEM observations provide evidences confirming the results of compressive strength and thermal conductivity. The role of w/c is insignificant on compressive strength and thermal conductivity of such type of concrete with very low density. The findings of this investigation revealed that infra-lightweight concrete with self-leveling ability, appropriate strength and different densities can be produce with giving more concern to the performed foam characteristics as well as the mixing technology.