Conventional Process Research Articles

Adsorptive and oxidative removal of phenolphthalein by sono-assisted synthesized FeAcC in advanced oxidation-integrated fluidized bed reactor

ABSTRACT Environmental water sources are under increasing threat due to the addition of harmful chemicals that are not addressed by conventional water treatment processes. To work on this concern, the current study aimed to synthesize sono-assisted Fe-modified activated carbon–chitosan (FeAcC) composite and construct a laboratory-scale ozone-integrated fluidized bed reactor (FBR) to eliminate phenolphthalein (php). After 120 min of incubation, the adsorbent demonstrated a 27.28 mg g−1 of php adsorption capacity at a pH of 4 with 0.5 g L−1 of adsorbent dosage. The adsorption efficacy and mechanism were defined using isotherm and kinetic models. The study investigated the impact of different factors, including initial concentration, reuse of FeAcC, recirculation flow rate, and hydraulic retention time (HRT), on the efficiency of php removal. The optimum removal efficiency was observed at approximately 95% after 20 min of operation at 1.5 L min−1 recirculation flow rate (batch FBR) and 70 min of HRT (continuous FBR) under a 400 mg h−1 ozonation rate. Experimental parameters were optimized using response surface methodology with central composite design to improve php removal. The large-scale implementation of the findings in the future can be a step for adding new technology for clean water treatment processes for emerging toxic organic pollutants.

Adsorptive and oxidative removal of phenolphthalein by sono-assisted synthesized FeAcC in advanced oxidation-integrated fluidized bed reactor

ABSTRACT Environmental water sources are under increasing threat due to the addition of harmful chemicals that are not addressed by conventional water treatment processes. To work on this concern, the current study aimed to synthesize sono-assisted Fe-modified activated carbon–chitosan (FeAcC) composite and construct a laboratory-scale ozone-integrated fluidized bed reactor (FBR) to eliminate phenolphthalein (php). After 120 min of incubation, the adsorbent demonstrated a 27.28 mg g−1 of php adsorption capacity at a pH of 4 with 0.5 g L−1 of adsorbent dosage. The adsorption efficacy and mechanism were defined using isotherm and kinetic models. The study investigated the impact of different factors, including initial concentration, reuse of FeAcC, recirculation flow rate, and hydraulic retention time (HRT), on the efficiency of php removal. The optimum removal efficiency was observed at approximately 95% after 20 min of operation at 1.5 L min−1 recirculation flow rate (batch FBR) and 70 min of HRT (continuous FBR) under a 400 mg h−1 ozonation rate. Experimental parameters were optimized using response surface methodology with central composite design to improve php removal. The large-scale implementation of the findings in the future can be a step for adding new technology for clean water treatment processes for emerging toxic organic pollutants.

Machine learning system for commercial banana harvesting

The conventional process of visual detection and manual harvesting of the banana bunch has been a known problem faced by the agricultural industry. It is a laborious activity associated with inconsistency in the inspection and grading process, leading to post-harvest losses. Automated fruit harvesting using computer vision empowered by deep learning could significantly impact the visual inspection process domains, allowing consistent harvesting and grading. To achieve the goal of the industry-level harvesting process, this work collects data from professional harvesters from the industry. It investigates six state-of-the-art architectures to find the best solution. 2,685 samples were collected from four different sites with expert opinions from industry harvesters to cut (or harvest) and keep (or not harvest) the banana brunch. Comparative results showed that the DenseNet121 architecture outperformed the other examined architectures, reaching a precision, recall, F1 score, accuracy, and specificity of 85%, 82%, 82%, 83%, and 83%, respectively. In addition, an understanding of the underlying black box nature of the solution was visualized and found adequate. This visual interpretation of the model supports human expert’s criteria for harvesting. This system can assist or replace human experts in the field.

Improvement in Natural Antioxidant Recovery from Sea Buckthorn Berries Using Predictive Model-Based Optimization

Sea buckthorn berries (SBB) are well known for being rich in natural bioactive compounds with high pharmacological activity. In this study, the optimization of extraction parameters was performed to recover phenolic compounds with high antioxidant activity from SBB. This study involved a systematic optimization approach, including screening for a variety of parameters, including temperature, time, ethanol concentration, agitation, and solid loading. On the basis of Plackett–Burman design (PBD) model, the two most significant parameters (agitation and solid loading) were selected, and the correlation model between those parameters and multiple responses was derived via response surface methodology (RSM). As a result, the optimal extraction condition for maximizing phenolic content and antioxidant activity was determined to be agitation at 109.54 rpm and a solid loading of 172.67 g/L. Under optimal conditions, SBB extract showed a total phenolic content of 0.21 mg/mL and ABTS and DPPH activities of 27.27% and 58.16%, respectively. The SBB extract prepared under optimal conditions was found to contain caffeic acid, vanillic acid, rutin, and vitamin B1 (thiamine). This work is the first challenge to design an optimization model for the efficient recovery of antioxidants from SBB and is significant in that the model can be applied simply and economically to conventional extraction processes.

Processing and performance of ultra high temperature ceramic matrix composite (UHTCMCs) using radio frequency assisted chemical vapour infiltration (RF-CVI)

Ultra-high temperature ceramic matrix composites (UHTCMCs) have been produced using a radio frequency assisted chemical vapour infiltration (RF-CVI) process. The composites were based on 2.5D carbon fibre preforms with a 0 / 90° (out of plane) fibre orientation and containing 23 % fibre volume fraction. These were initially impregnated with zirconium diboride (ZrB2) powder in the form of a slurry and then, after solvent removal, the majority of the porosity filled with pyrolytic carbon (PyC) using the RF-CVI process at 1273 K and 0.5 kPa chamber pressure. The latter resulted in a uniform rough laminar texture with good interfacial bonding. As intended, an inverse temperature profile was achieved using the RF heating, enabling uniform densification of the preform from the inside out, with no entrapped porosity and achieving 90 % of theoretical density in only 24 h, at least a tenfold reduction in processing time compared to the conventional CVI process and a fivefold reduction compared to other modified CVI processes such as forced flow or pressure gradient CVI. The resulting UHTCMCs displayed good mechanical strength and thermo-ablative behaviour.

A techno-economic assessment of conventional and modified Solvay processes for CO2 capture and reject brine desalination

The ongoing discharge of desalination reject brine and emission of carbon dioxide (CO2) into the environment pose a major threat to the ecosystem. In this context, the Solvay process presents a potential mitigation scheme for reducing reject brine salinity while simultaneously sequestering CO2. This work reports for the first time a systematic techno-economic assessment of the conventional (ammonia-based) and modified (calcium hydroxide-based and Potassium hydroxide-based) Solvay processes. The model evaluates the effect of reactor conversion, inlet CO2 weight%, inlet CO2 temperature, gas/liquid ratio, and brine flow rate on the CO2 and Sodium ions removal. In addition, the process cost associated with each parameter was analyzed, and the impact of implementing carbon tax on process profitability was investigated. Furthermore, the Solvay processes were evaluated using economic metrics including Net Present Value (NPV), economy of scale, and Levelized cost of water. The results suggest that the calcium hydroxide-based modified Solvay process outperforms other processes in terms of CO2 and Sodium ions removal. Moreover, for the studied parameters, the calcium hydroxide-based modified Solvay process demonstrated economic viability, yielding a decent annual profit. However, the conventional Solvay process requires a remarkable amount of expenses, yet after the implementation of 40 dollars per metric tons of CO2 as a carbon tax, the conventional Solvay reaches the break-even point. These findings underscore the importance of implementing environmentally friendly practices in the industry, as the modified Solvay process proves to be a promising solution for mitigating environmental threats and promoting sustainable operations.

Unveiling niobium pentoxide and cerium oxide-dispersed ferritic stainless steel for solid oxide fuel cells interconnects

Herein, the effect of niobium pentoxide (Nb2O5) and nano-sized cerium oxide (CeO2) on oxidation behavior and area specific resistance (ASR) of the ferritic stainless steel has been investigated for the development of robust metallic interconnects. An oxide-dispersed ferritic stainless steel alloy is fabricated using the powder metallurgy (PM) process. The morphologies of the alloy before and after oxidation are observed through Scanning Electron Microscope (SEM), Scanning Transmission Electron Microscopy (STEM) and Secondary Ion Mass Spectrometry (SIMS) analyses. Addition of Nb2O5 in the alloy formed a C14 Laves phase of (Fe, Cr)2(Nb, Si). The Laves phase and CeO2 controlled the oxidation behavior of the ferritic stainless steels, consequently reducing the oxide scale thickness and improving the ASR. An alloy with 1 wt% Nb2O5 and 3 wt% CeO2 showed an ASR value of 27.1 mΩ cm2 at 800 °C for 1000 h, which is similar to the ASR value of the commercial Fe–Cr alloy. The results of this study indicate that Nb2O5 and CeO2-dispersed ferritic stainless steel using the PM process can be more advantageous than the conventional process for manufacturing metallic interconnects with complex shapes and reducing production costs.

Cryomilled electrospun nanofiber mats containing d-mannitol exhibit suitable for aerosol delivery of proteins

Dry powder inhalers (DPIs) are the first choice for inhalation drug development. However, some conventional DPI formulation processes require heating, which may damage high molecular weight drugs such as proteins and nucleic acids. In this study, we propose a novel DPI preparation process that avoids the use of heat. Dry powders were prepared by cryomilling nanofiber mats composed of polyvinyl alcohol, D(−)-mannitol (Man), and α-chymotrypsin (α-Chy) as the model drug using the electrospinning method. The addition of Man conferred high dispersibility and excellent in vitro aerosol performance to the nanofiber mat powder in a very short milling time (less than 0.5 min) as assessed using the Andersen cascade impactor. Powders were classified according to the degree of friability, and among these, nanofiber mats containing 15 % Man and milled for 0.25 min exhibited the highest aerosol performance. Nanofiber mats containing Man milled for less than 0.5 min also exhibited greater α-Chy enzymatic activity than a nebulized α-Chy solution. Furthermore, single inhalation induced no significant lung tissue damage as evidenced by lactate dehydrogenase activity assays of mouse bronchoalveolar lavage fluid. This novel DPI formulation process may facilitate the safe and efficient inhalational delivery of therapeutic proteins.

Mechanical strength of an hot-mix asphalt using recycled concrete aggregate: mass and volume proportioning

The generation of solid waste produced by the construction sector is considered a major problem worldwide. Several studies have been conducted to evaluate the use of construction and demolition wastes (CDW) in pavements. Within CDW, one material with great potential for use is recycled concrete aggregate (RCA). The present study evaluated the mechanical performance of a hot-mix asphalt (HMA) that used RCA as a partial substitute for the coarse fraction of the natural aggregate – Nag (particle size retained on 1/2” and 1/2"+3/8” sieves). The substitution was performed in a conventional way by mass and also by volume. To evaluate the performance under monotonic loading, the stability/flow ratio (S/F) of the Marshall test and the Indirect Tensile Strength (ITS) were measured on dry (ITSd) and conditioned (immersed in water, ITSw) samples. The tensile strength ratio (TSR) was calculated to evaluate the resistance to moisture damage. Under cyclic loading, tests of resilient modulus – RM (three temperatures and three loading frequencies), permanent deformation, and fatigue resistance under controlled-stress were performed. Cantabro tests were performed to measure the resistance to abrasive wear. Conventional characterization tests and imaging processing in a scanning electron microscope (SEM) were carried out on particles of RCA and Nag. A Life Cycle Cost Analysis (LCCA) was performed with the results obtained. The general conclusions were as follows: (i) RCA increases the asphalt content in the mixes, however, volume substitution could help to decrease it; (ii) the mixes with RCA met the volumetric and strength parameters established by the Colombian specification (especially for roads with low traffic volumes); (iii) mixes with RCA undergo better mechanical performance in all tests performed, however, resistance to moisture damage may be compromised when dosing by volume and asphalt content decreases; (iv) substitution by mass or volume did not generate clear trends in the results, but better overall performance is reported in mixes dosed by volume. It is recommended to carry out more studies where Nag is replaced by RCA in volume.

Orientation-dependent Andreev reflection in an altermagnet/altermagnet/superconductor junction

Altermagnets, an emerging class of magnetic materials distinguished by a significant non-relativistic spin splitting band structure but zero net macroscopic magnetization, have recently received considerable attention. Here, we present a theoretical study focusing on the orientation-dependent conductance induced by Andreev reflection (AR) at an altermagnet/altermagnet/superconductor junction. Conventional and equal-spin AR processes occur when the Néel vector directions of the AMs are non-collinear and controllable by the altermagnet’s orientation θ and Néel vector direction α. The conductance spectra resemble ferromagnet/ferromagnet/superconductor junctions with parallel or antiparallel magnetization configurations, depending on θ and α. Both the anisotropic altermagnetic state and the equal-spin AR signature can be probed by studying conductance spectra. These findings suggest that altermagnet/superconductor junctions are promising platforms for future superconducting spintronics applications.

Nanoarchitectonics of hydrothermal carbonized sugarcane juice-derived biochar for high supercapacitance and dye adsorption performance

Here, we report the exfoliation of micron-sphere biochar to a few layers using the conventional KOH activation process. Micron-sphere biochar is obtained from hydrothermal carbonization (HTC) of sugarcane juice (Saccharum officinarum). HR-TEM and Raman spectroscopy studies revealed the conversion of micron-sphere biochar (MSB) to a few layers of biochar (FLB) in the activation process. BET characterization revealed FLB with a high surface area of 681.21 m2/g having mesopores. Consequently, an electrochemical study demonstrated excellent supercapacitor performance with a specific capacitance of 964.5 F/g and an energy density of 33.11 Wh/kg at a maximum power density of 936 W/kg. Batch adsorption studies showed rapid Methylene blue (MB) dye adsorption in 10 min. The equilibrium data analysis indicated the Langmuir adsorption isotherm with a correlation coefficient of 0.99. Evaluation of the kinetic models suggests that pseudo-second-order kinetics is the most appropriate model, implying that the adsorption of MB dye is primarily due to chemisorption. These findings suggest a Nanoarchitectonics of biochar into a few layers using traditional KOH activation, suitable for various applications.

3D printable elastomers with exceptional strength and toughness.

Three-dimensional (3D) printing has emerged as an attractive manufacturing technique because of its exceptional freedom in accessing geometrically complex customizable products. Its potential for mass manufacturing, however, is hampered by its low manufacturing efficiency (print speed) and insufficient product quality (mechanical properties). Recent progresses in ultra-fast 3D printing of photo-polymers1-5 have alleviated the issue of manufacturing efficiency, but the mechanical performance of typical printed polymers still falls far behind what is achievable with conventional processing techniques. This is because of the printing requirements that restrict the molecular design towards achieving high mechanical performance. Here we report a 3D photo-printable resin chemistry that yields an elastomer with tensile strength of 94.6 MPa and toughness of 310.4 MJ m-3, both of which far exceed that of any 3D printed elastomer6-10. Mechanistically, this is achieved by the dynamic covalent bonds in the printed polymer that allow network topological reconfiguration. This facilitates the formation of hierarchical hydrogen bonds (in particular, amide hydrogen bonds), micro-phase separation and interpenetration architecture, which contribute synergistically to superior mechanical performance. Our work suggests a brighter future for mass manufacturing using 3D printing.

Super compact and ultra-wideband bandpass filter with three band notches using triple-mode stepped impedance resonator and defected ground structure

A super-compact ultra-wideband (UWB) microstrip band-pass filter (BPF) with triple-notched bands and wide stopband is proposed in this paper. The super-compactness of the proposed filter is achieved by integrating the modified SCRLH-TL UWB-BPF and backbone-shaped defected ground structure (DGS). The equivalent LC circuit models of the DGS and the modified SCRLH-TL UWB-BPF with the DGS are analyzed to validate their numerical simulation results. To introduce the triple notched-bands to mitigate the interference the two triple-mode SIRs are designed and loaded on the modified UWB-BPF without increasing the circuit size. The proposed filter was fabricated by using a conventional PCB process with the substrate of FR4. The measured 3-dB passband ranges from 2.8 through 10.2 GHz with the fractional bandwidth (FBW) of about 114%. The triple-notched bands with attenuation of more than 15 dB are measured at 4.4, 5.3 and 8.2 GHz, respectively. The filter exhibits a high selectivity with steep skirt property and has a wide upper stopband with an out-of-band rejection of −10 dB at 11.8−20 GHz. Its total dimension, including the rectangular substrate with feed lines, occupies only 16mm × 8 mm.

Variation of Chemical Microenvironment of Pores in Hydrazone‐Linked Covalent Organic Frameworks for Photosynthesis of H2O2

Photocatalytic synthesis of H2O2 is an advantageous and ecologically sustainable alternative to the conventional anthraquinone process. However, achieving high conversion efficiency without sacrificial agents remains a challenge. In this study, two covalent organic frameworks (COF‐O and COF‐C) were prepared with identical skeletal structures but with their pore walls anchored to different alkyl chains. They were used to investigate the effect of the chemical microenvironment of pores on photocatalytic H2O2 production. Experimental results reveal a change of hydrophilicity in COF‐O, leading to suppressed charge recombination, diminished charge transfer resistance, and accelerated interfacial electron transfer. An apparent quantum yield as high as 10.3% (λ = 420 nm) can be achieved with H2O and O2 through oxygen reduction reaction. This is among the highest ever reported for polymer photocatalysts. This study may provide a novel avenue for optimizing photocatalytic activity and selectivity in H2O2 generation.

Techno-economic analysis of cleaner alternatives for recovering ammonium chloride from wastewater generated by polyvinyl chloride thermal stabilizer plants

The current conventional process for recovering NH4Cl from wastewater generated by organotin mercaptide-based polyvinyl chloride thermal stabilizer plants through evaporative crystallization is energy intensive and has not yet been discussed. Three energy-saving process variants, namely MVR, DEE, and TVR processes, have been proposed and evaluated in terms of both technical and economic feasibility, treating the case as a cost-cutting project aimed to avoid off-site wastewater treatment costs. Comparative evaluation has also been carried out with the conventional (CON) process used as a reference. Under the studied conditions, the MVR, DEE, and TVR processes provided energy savings in the ranges of 60%-76%, 35%-43%, and 26%-37%, respectively, confirming that applying the three alternative processes for recovering NH4Cl results in a significantly cleaner and more sustainable recovery process. Under typical conditions and with a plant capacity of 5000 kg/h, the MVR, DEE, and TVR processes required an additional investment of 2.3, 1.0, and 0.2 million USD, respectively, compared to the CON process. The revenue was primarily driven by cost savings due to the elimination of off-site wastewater treatment, which accounted for 86.9% of the total revenue. Sensitivity analysis showed that the off-site wastewater treatment cost was found to be the most influential factor on economic feasibility. When economic targets can be traded off, MVR process is highly recommended as an alternative to the conventional energy-intensive process. If economic feasibility comparable to the conventional process is still targeted, DEE and TVR are recommended. The results of this study dismiss concerns that cleaner processes would have a negative economic impact.

Closed-Loop recovery of spent lithium-ion batteries based on preferentially selective extraction of lithium strategy

From the perspective of sustainable energy utilization and green economic development, efficient and closed-loop recovery of spent lithium-ion batteries (LIBs) is imperative. This work has developed a closed-loop recovery process for spent LIBs based on preferentially selective extraction of lithium. After molten salt assisted roasting, the efficiency for preferential extraction of Li+ could be high up to 99.3 % after optimization of selectivity. Dilute sulfuric acid alone facilitated the leaching efficiency of valuable metals over 98 %, eliminating the need for reductants. Regeneration of residue into graphite and recovery of NaCl mixed powder could avoid the wastage of residual metals. Compared with the conventional process, this work shows a high recovery efficiency and closed-loop extent, with a profit of $6,820 per ton of recovered spent LIBs. This work provides a more environmentally friendly recovery strategy with higher economic profits and environmental impacts, thereby enhancing the potential for industrial applications.

A novel strategy for recovery of heavy metals and synthesis of Co-rich alloy from the alkali-treated tungsten residue using photovoltaic silicon kerf waste

The treatment of spent cemented carbides using the conventional alkali-acid leaching process results in the generation of hazardous solid waste tungsten leaching residue. This study proposed an alternative process using the alkali-treated tungsten leaching residue (AW-residue) without the acid leaching step, preserving Co in the residue. By using photovoltaic silicon kerf waste (SKW) as a reducing agent, heavy metals (Co, Ni, W, Nb, and Ta) were efficiently extracted from AW-residue and a Co-rich alloy was obtained. The silicothermic reduction process facilitated the recovery of iron group metals (Co, Ni, and Fe) and effectively captured trace refractory metals (W, Ta, and Nb). Phase separation occurred through reduction reaction and viscosity-driven processes between the Co-rich alloy and the slag. Optimal conditions were identified as 20% SKW addition, MgO crucible, and a holding time of 120min, achieving a total recovery yield of 95.5%, with specific yields for Co (97.7%), Ni (97.0%), W (82.5%), Nb (76.3%), and Ta (70.5%). A 20kg pilot-scale experiment confirmed the feasibility of the process, yielding 47.0% Co-rich alloy from AW-residue compared to 48.3% in lab-scale experiment, and producing a harmless slag phase. This environmentally friendly approach promotes sustainable recycling of valuable metals in the tungsten industry. Environmental ImplicationHazardous leaching residue (AW-residue) derived from the hydrometallurgical recycling of spent cemented carbides poses significant environmental hazards, as it cannot be disposed of via landfill or direct smelting. Importantly, the presence of heavy valuable metals (e.g., Co, Ni, W, Nb, and Ta) in the AW-residue leads to substantial resource wastage. A novel strategy for the effective recovery of these valuable metals from AW-residue involves utilizing photovoltaic silicon kerf waste (SKW) as a reducing agent. This approach not only achieves waste disposal using waste, but also minimizes environmental risks.

Statistical analysis of vertically stacked nanosheet complementary FET based on polycrystalline silicon with multiple grain boundaries

In this study, a complementary field-effect transistor (CFET) based on a polycrystalline silicon (poly-Si) stacked-nanosheet (NS) structure with a grain boundary (GB) is designed and analyzed using a technology computer-aided design (TCAD) simulation. The advantage of the CFET using a poly-Si is that the active cell region can be reduced by 50 % because the p-type transistors are vertically stacked on the n-type transistors. In addition, it is possible to replace the conventional CMOS process and fabricate a three-dimensional vertically stacked structure at a low cost. To consider the effect of the GB in poly-Si, we assumed that there is a single GB at the center of the body region. By optimizing the geometrical parameters of the proposed CFET, the transfer characteristics of the NMOS and PMOS transistors, such as the threshold voltage (Vth), on current (Ion), off current (Ioff), and subthreshold swing (SS), are symmetrical. The proposed CFET demonstrated a superior logic performance of NML = 0.299 V and NMH = 0.297 V at an operation voltage of VDD = 0.65 V. To consider random GBs in the poly-Si, we assumed that five GBs existed in the proposed CFET, and the variation in CMOS logic inverter characteristics are statistically analyzed. As a result, the RSDs for Vm of the NMOS and PMOS transistors are 2.067 % and 0.293 %, and the RSDs of the pull-down delay time (tpHL) and pull-up delay time (tpLH) are 5.320 % and 3.244 %, respectively. An acceptor-like traps with high trap density are dominant in the proposed CFET, and this trend is similar across the 1024 samples. Nevertheless, most of the differences are within 5 % and the proposed CFET exhibited stability against GBs and the potential to replace the conventional CMOS logic inverters.

Exploring the effect of facile i-line photolithography on the structure and physicochemical properties of photosensitive glass ceramics

Photosensitive glass-ceramics exhibit significant potential to replace silicon materials in the microfabrication of micro-electro-mechanical-system (MEMS) devices. However, they are constrained by the limitations of a conventional 320-nm photolithography process. Therefore, developing an ideal industrial i-line (365 nm) photolithography for Li2O-Al2O3-SiO2 photosensitive glass-ceramics is urgently needed. This study initially explores the impact of a facile i-line photolithography on the structure and physicochemical properties of photosensitive glass ceramics. We experimentally showcase a direct, scalable, and straightforward i-line photolithography technique for Li2O-Al2O3-SiO2 photosensitive glass ceramics. Our research concentrates on how the exposure time affects the properties of Li2O-Al2O3-SiO2 photosensitive glass ceramics, particularly regarding nucleation and crystallization. This is achieved by adjusting the exposure time parameter and utilizing XRD, etching experiments, SEM, TEM, and other tests under a i-line light source. By optimizing the exposure process parameters, we also modify the annealing process parameters affecting the crystallization of lithium metasilicate in the exposed areas. Under a treatment process involving an exposure time of 20 minutes, a nucleation temperature of 500°C, a crystallization temperature of 630°C, and a nucleation/crystallization duration of 2 hours, the sample achieves the highest crystal quantity and the optimal thickness-etching rate ratio.

Elucidating the influence mechanisms of splat cooling on microstructure evolution in friction stir welding of 2195 Al–Li alloy by multi-scale simulation

Al–Li alloy has been widely used in the manufacture of aerospace aircraft structural parts due to its high specific strength and excellent comprehensive performance. Friction stir welding (FSW), as a solid-state joining technique, generates comparatively lower heat generation in contrast to fusion welding. However, even with this reduced heat input, the welded joints of 2195 Al–Li alloy still exhibit noticeable thermal softening. FSW is very sensitive to welding heat input, and the thermal cycle of high peak temperature coarsens the grain in the weld zone, thereby reducing joint properties. To overcome these problems, external cooling can be applied to reduce peak temperature and increase cooling speed, improving the performance of FSW joints. In order to study the mechanism of external cooling on the microstructure evolution of joints, this work established a multi-scale simulation of splat cooling assisted friction stir welding (SCaFSW) of 2195 Al–Li alloy. The temperature change and material deformation data in SCaFSW were calculated in the macroscopic finite element model and used for further Monte Carlo microstructure evolution simulation, and compared with the conventional FSW process. Results reveal that the splat cooling significantly reduces the area of the high temperature region of the workpiece, decreasing the temperature at the same location 10 mm behind the tool by approximately 50 °C compared to FSW. While the local temperature field around the tool pin is not affected by the splat cooling, which mainly accelerates the cooling rate of the welded joint and reduces the plastic strain. In addition, the dislocation density in the weld nugget zone (WNZ) of SCaFSW joint is higher than that in conventional FSW, which promotes the process of grain nucleation and finally refines the grain in the WNZ. The simulated average grain size and thermal cycling results are in good agreement with the experimental results.