Microstructure and damping properties of LPSO phase dominant Mg-Ni-Y and Mg-Zn-Ni-Y alloys

This work studied the microstructure,mechanical properties and damping properties of Mg_(95.34)Ni_(2)Y_(2.66) and Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloys systematically.The difference in the evolution of the long-period stacked ordered(LPSO)phase in the two alloys during heat treatment was the focus.The morphology of the as-cast Mg_(95.34)Ni_(2)Y_(2.66)presented a disordered network.After heat treatment at 773 K for 2 hours,the eutectic phase was integrated into the matrix,and the LPSO phase maintained the 18R structure.As Zn partially replaced Ni,the crystal grains became rounded in the cast alloy,and lamellar LPSO phases and more solid solution atoms were contained in the matrix after heat treatment of the Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloy.Both Zn and the heat treatment had a significant effect on damping.Obvious dislocation internal friction peaks and grain boundary internal friction peaks were found after temperature-dependent damping of the Mg_(95.34)Ni_(2)Y_(2.66)and Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloys.After heat treatment,the dislocation peak was significantly increased,especially in the alloy Mg_(95.34)Ni_(2)Y_(2).66.The annealed Mg_(95.34)Ni_(2)Y_(2.66)alloy with a rod-shaped LPSO phase exhibited a good damping performance of 0.14 atε=10^(−3),which was due to the difference between the second phase and solid solution atom content.These factors also affected the dynamic modulus of the alloy.The results of this study will help in further development of high-damping magnesium alloys.

First Principles Calculations for Corrosion in Mg-Li-Al Alloys with Focus on Corrosion Resistance: A Comprehensive Review

This comprehensive review examines the structural,mechanical,electronic,and thermodynamic properties of Mg-Li-Al alloys,focusing on their corrosion resistance and mechanical performance enhancement.Utilizing first-principles calculations based on Density Functional Theory(DFT)and the quasi-harmonic approximation(QHA),the combined properties of the Mg-Li-Al phase are explored,revealing superior incompressibility,shear resistance,and stiffness compared to individual elements.The review highlights the brittleness of the alloy,supported by B/G ratios,Cauchy pressures,and Poisson’s ratios.Electronic structure analysis shows metallic behavior with varied covalent bonding characteristics,while Mulliken population analysis emphasizes significant electron transfer within the alloy.This paper also studied thermodynamic properties,including Debye temperature,heat capacity,enthalpy,free energy,and entropy,which are precisely examined,highlighting the Mg-Li-Al phase sensitive to thermal conductivity and thermal performance potential.Phonon density of states(PHDOS)confirms dynamic stability,while anisotropic sound velocities reveal elastic anisotropies.This comprehensive review not only consolidates the current understanding of the Mg-Li-Al alloy’s properties but also proposes innovative strategies for enhancing corrosion resistance.Among these strategies is the introduction of a corrosion barrier akin to the Mg-Li-Al network,which holds promise for advancing both the applications and performance of these alloys.This review serves as a crucial foundation for future research aimed at optimizing alloy design and processing methods.

Paraelectric Doping Simultaneously Improves the Field Frequency Adaptability and Dielectric Properties of Ferroelectric Materials:A Phase-Field Study

Recent years,the polarization response of ferroelectrics has been entirely studied.However,it is found that the polarization may disappear gradually with the continually applied of electric field.In this paper,taking K0.48Na0.52NbO3(KNN)as an example,it was demonstrated that the residual polarization began to decrease when the electric field frequency increased to a certain extent using a phase-field methods.The results showed that the content of out-of-plane domains increased first and then decreased with the increase of applied electric field frequency,the maximum polarization disappeared at high frequencies,and the hysteresis loop became elliptical.In order to further study the abnormal changes of hysteresis loops of ferroelectrics under high electric field frequency,we analyzed the hysteresis loop and dielectric response of solid solution 0.1SrTiO_(3)-0.9K_(0.48)Na_(0.52)NbO_(3).It was found that the doped hysteresis loop maintained its shape at higher frequency and the dielectric constant increased.This kind of doping has a higher field frequency adaptability,which has a key guiding role in improving the dielectric properties of ferroelectric thin films and expanding the frequency application range of ferroelectric nano memory。

Phase-field simulation of lack-of-fusion defect and grain growth during laser powder bed fusion of Inconel 718

The anisotropy of the structure and properties caused by the strong epitaxial growth of grains during laser powder bed fusion(L-PBF)significantly affects the mechanical performance of Inconel 718 alloy components such as turbine disks.The defects(lack-of-fusion Lo F)in components processed via L-PBF are detrimental to the strength of the alloy.The purpose of this study is to investigate the effect of laser scanning parameters on the epitaxial grain growth and LoF formation in order to obtain the parameter space in which the microstructure is refined and LoF defect is suppressed.The temperature field of the molten pool and the epitaxial grain growth are simulated using a multiscale model combining the finite element method with the phase-field method.The LoF model is proposed to predict the formation of LoF defects resulting from insufficient melting during L-PBF.Defect mitigation and grain-structure control during L-PBF can be realized simultaneously in the model.The simulation shows the input laser energy density for the as-deposited structure with fine grains and without LoF defects varied from 55.0–62.5 J·mm^(-3)when the interlayer rotation angle was 0°–90°.The optimized process parameters(laser power of 280 W,scanning speed of 1160 mm·s^(-1),and rotation angle of 67°)were computationally screened.In these conditions,the average grain size was 7.0μm,and the ultimate tensile strength and yield strength at room temperature were(1111±3)MPa and(820±7)MPa,respectively,which is 8.8%and10.5%higher than those of reported.The results indicating the proposed multiscale computational approach for predicting grain growth and Lo F defects could allow simultaneous grain-structure control and defect mitigation during L-PBF.

Dissolution and reprecipitation of 14H-LPSO structure accompanied by dynamic recrystallization in hot-extruded Mg_(89)Y_(4)Zn_(2)Li_(5) alloy

We investigate the variation induced in long-period stacking ordered(LPSO)structures,dynamic recrystallization(DRX),and mechanical performance of hot-extruded Mg89Y4Zn2Li5 alloys fabricated at different extrusion speeds(Ve=0.4,0.8,1.0,1.2 mm/s)and die angles(α=30°,60°,90°)under 400℃,the dissolution and reprecipitation of 14H LPSO structure accompanied by DRX process are then clarified in detail.Upon all extrusion conditions,the block 18R LPSO structures elongate in the extrusion direction,while the lamellar 14H LPSO structures dissolve under the deformation strain.In addition,due to discontinuous and continuous DRX mechanisms,all hot-extruded alloys have a full DRX microstructure consisting of equiaxed recrystallized grains,but the DRX grain size reduces when both extrusion speed and die angle decrease.Note that,in the interior of DRX grains,thin LPSO lamellae mixing 14H,18R and 24R structures nucleate and dynamically precipitate due to the dissolution of the original lamellar 14H LPSO structures.Furthermore,the hot-extruded Mg_(89)Y_(4)Zn_(2)Li_(5)alloy becomes stronger as decreasing of the extrusion speed and die angle,whereas the ductility remains nearly constant.Finally,the hotextruded Mg_(89)Y_(4)Zn_(2)Li_(5)alloy achieves an excellent strength-ductility balance at a relatively low extrusion speed(0.4 mm/s)and small die angle(30°)mainly due to the elongated 18R LPSO structure,fine and full DRX microstructure,thin mixed LPSO precipitates in the DRX grains,twins and dislocations.

Phase-Field Simulation of δ Hydride Precipitation with Interfacial Anisotropy

Previous studies ofδhydride in zirconium alloys have mainly assumed an isotropic interface.In practice,the difference in crystal structure at the interface between the matrix phase and the precipitate phase results in an anisotropic interface.With the purpose of probing the real evolution ofδhydrides,this paper couples an anisotropy function in the interfacial energy and interfacial mobility.The influence of anisotropic interfacial energy and interfacial mobility on the morphology ofδhydride precipitation was investigated using the phase-field method.The results show that the isotropy hydride precipitates a slate-like morphology,and the anisotropicδhydride precipitates at the semi-coherent and non-coherent interfaces exhibited parallelogram-like and needle-like,which is consistent with the actual experimental morphology.Compared with the coherent interface,the semi-coherent or non-coherent interface adjusts the lattice mismatch,resulting in lower gradient energy that is more consistent with the true interfacial state.Simultaneously,an important chain of relationships is proposed,in the range of I_(x)<I_(y)<1.5I_(x)(I_(y)<I_(x) or I_(y)>1.5I_(x)),with the increase of the anisotropic mobility I_(y) in the y-axis,the gradient energy increases(decreases),the tendency of the non-coherent(semi-coherent)relationship at the interface,and the precipitation rate of hydride decreases(increases).Furthermore,the inhomogeneous stress distribution around the hydride leads to a localized enrichment of the hydrogen concentration,producing a hydride tip.The study of interfacial anisotropy is informative for future studies ofδhydride precipitation orientation and properties.

Machine Learning Design of Aluminum-Lithium Alloys with High Strength

Due to the large unexplored compositional space,long development cycle,and high cost of traditional trial-anderror experiments,designing high strength aluminum-lithium alloys is a great challenge.This work establishes a performance-oriented machine learning design strategy for aluminum-lithium alloys to simplify and shorten the development cycle.The calculation results indicate that radial basis function(RBF)neural networks exhibit better predictive ability than back propagation(BP)neural networks.The RBF neural network predicted tensile and yield strengths with determination coefficients of 0.90 and 0.96,root mean square errors of 30.68 and 25.30,and mean absolute errors of 28.15 and 19.08,respectively.In the validation experiment,the comparison between experimental data and predicted data demonstrated the robustness of the two neural network models.The tensile and yield strengths of Al-2Li-1Cu-3Mg-0.2Zr(wt.%)alloy are 17.8 and 3.5 MPa higher than those of the Al-1Li4.5Cu-0.2Zr(wt.%)alloy,which has the best overall performance,respectively.It demonstrates the reliability of the neural network model in designing high strength aluminum-lithium alloys,which provides a way to improve research and development efficiency.

Erratum to:Phase-field simulation of lack-of-fusion defect and grain growth during laser powder bed fusion of Inconel 718

The original online version of this article unfortunately contained a mistake.The reference[24]in the original online version is incorrect.The correct version is given below:Y.H.Cheng,Numerical Simulation and Experimental Research of Selective Laser Melting on Nickel Based Alloy Powder GH4169[Dissertation],North University of China,Taiyuan,2016.

Application of Solution-Focused Approach in Nursing Care of Advanced Schistosomiasis

Objective:To analyze the effect of solution-focused approach on advanced schistosomiasis(AS).Methods:10 cases of patients with AS that were treated with a solution-focused approach were included in our study.The indicators before and after the intervention were measured(knowledge mastery,prevention and treatment compliance,personal behavior,self-care ability,management satisfaction,complication rate).Results:After analyzing pre-and post-intervention indicators,statistical significance was found(P<0.05).The intervention received a satisfaction rate of 80.00%,with a complication rate of 10.00%.Conclusion:Using a solution-focused approach for ankylosing spondylitis(AS)patients can enhance their understanding and attitude toward disease prevention and treatment,improve their behaviors and self-care ability,resulting in high satisfaction and reduced complications.

Total phenols, flavonoids, and procyanidins levels and total antioxidant activity of different Korean pine(Pinus koraiensis) varieties

Total phenols,flavonoids,procyanidins,and total antioxidant capacity,measured with ferric reducing antioxidant power,radical scavenging capacity,and oxygen radical absorption capacity assays were first evaluated in the extracts of the shells,skins and kernels of 10 varieties of Pinus koraiensis.Results indicate that these varieties had strong radical scavenging capacities,ferric reducing antioxidant power and oxygen radical absorption capacities.Phenolic,flavonoid and procyanidin values ranged from 138.6(#3 kernel)to 518.6(#10 shell)mg GAE/g,from 23.3(#2 kernel)to 70.8(#5 skin)mg RE/g,from 2.5(#2 kernel)to 142.1(#7 skin)mg CE/g,respectively.Radical scavenging capacity and ferric reducing antioxidant power values were positively correlated to the polyphenol contents which play a major role in antioxidant properties.The varieties may be divided into two groups by cluster analysis and the variables being measured.These results will be useful for breeding varieties and guiding their production.

Special function of nestin^+ neurons in the medial septum-diagonal band of Broca in adult rats

Nestin＋ neurons have been shown to express choline acetyltransferase （CHAT） in the medial septum-diagonal band of Broca in adult rats. This study explored the projection of nestin＋ neu-rons to the olfactory bulb and the time course of nestin＋ neurons in the medial septum-diagonal band of Broca in adult rats during injury recovery after olfactory nerve transection. This study observed that all nestin＋ neurons were double-labeled with ChAT in the medial septum-diagonal band of Broca. Approximately 53.6% of nestin~ neurons were projected to the olfactory bulb and co-labeled with fast blue. A large number of nestin~ neurons were not present in each region of the medial septum-diagonal band of Broca. Nestin＋ neurons in the medial septum and vertical limb of the diagonal band of Broca showed obvious compensatory function. The number of nestin＋ neurons decreased to a minimum later than nestin/CHAT＋ neurons in the medial sep- turn-diagonal band of Broca. The results suggest that nestin＋ cholinergic neurons may have a closer connection to olfactory bulb neurons. Nestin＋ cholinergic neurons may have a stronger tolerance to injury than Nestin/CHAT＋ neurons. The difference between nestin＋ and nestin-/ ChAT＋ neurons during the recovery process requires further investigations.

Recognition and Visualization of Lithography Defects based on Transfer Learning

Yield control in the integrated circuit manufacturing process is very important,and defects are one of the main factors affecting chip yield.As the process control becomes more and more critical and the critical dimension becomes smaller and smaller,the identification and location of defects is particularly important.This paper uses a machine learning algorithm based on transfer learning and two fine-tuned neural network models to realize the autonomous recognition and classification of defects even the data set is small,which achieves 94.6%and 91.7%classification accuracy.The influence of network complexity on classification result is studied at the same time.This paper also establishes a visual display algorithm of defects,shows the process of extracting the deep-level features of the defective image by the network,and then analyze the defect features.Finally,the Gradient-weighted Class Activation Mapping technology is used to generate defect heat maps,which locate the defect positions and probability intensity effects.This paper greatly expands the application of transfer learning in the field of integrated circuit lithography defect recognition,and greatly improves the friendliness of defect display.

Integrated unified phase-field modeling(UPFM)

For a long time,the phase-field method has been considered a mesoscale phenomenological method that lacks physical accuracy and is unable to be closely linked to the mechanical or functional properties of materials.Some misunderstandings existing in these viewpoints need to be clarified.Therefore,it is necessary to propose or adopt the perspective of“unified phase-field modeling(UPFM)”to address these issues,which means that phase-field modeling has multiple unified characteristics.Specifically,the phase-field method is the perfect unity of thermodynamics and kinetics,the unity of multi-scale models from microto meso and then to macro,the unity of internal or/and external driving energy with order parameters as field variables,the unity of multiple physical fields,and thus the unity of material composition design,process optimization,microstructure control,and performance prediction.It is precisely because the phase-field approach has these unified characteristics that,after more than 40 years of development,it has been increasingly widely applied in materials science and engineering.

Subgrain-assisted spontaneous grain refinement in rapid solidification of undercooled melts

The grain refinement mechanism for rapid solidification of undercooled melts is still an open problem even after 60 years of on-going studies.In this work,rapid solidification of undercooled Ni and equi-atomic FeCoNiPd melts was studied and spontaneous grain refinement was found at both low and high undercooling.After a detailed electron backscattered diffraction analysis,subgrain-induced grain orien-tation scattering and splitting were found to occur along with the transition from coarse dendrites to fine equiaxed grains at low and high undercooling,respectively,indicating that subgrains play an im-portant role during the formation of fine equiaxed grains.On this basis,a compromise mechanism of subgrain-assisted spontaneous grain refinement was proposed.Because the dendrite re-melting induced thermo-mechanical process and fluid flow induced dendrite deformation occur simultaneously during the post-recalescence stage,stress accumulation would be maximum at both low and high undercooling,thus inducing dynamic recrystallization,during which the formation and rotation of subgrains make the grain orientations scattering and even splitting.Furthermore,the grain/subgrain size of undercooled FeCoNiPd ascribing to its unique co-segregation behavior keeps almost invariable from low to high undercooling,indicating that the co-segregation strategy would be effective to inhibit grain growth after rapid solidifi-cation and would be useful in practice.

Machine Learning-Based Research on Tensile Strength of SiC-Reinforced Magnesium Matrix Composites via Stir Casting

SiC is the most common reinforcement in magnesium matrix composites,and the tensile strength of SiC-reinforced magnesium matrix composites is closely related to the distribution of SiC.Achieving a uniform distribution of SiC requires fine control over the parameters of SiC and the processing and preparation process.However,due to the numerous adjustable parameters,using traditional experimental methods requires a considerable amount of experimentation to obtain a uniformly distributed composite material.Therefore,this study adopts a machine learning approach to explore the tensile strength of SiC-reinforced magnesium matrix composites in the mechanical stirring casting process.By analyzing the influence of SiC parameters and processing parameters on composite material performance,we have established an effective predictive model.Furthermore,six different machine learning regression models have been developed to predict the tensile strength of SiC-reinforced magnesium matrix composites.Through validation and comparison,our models demonstrate good accuracy and reliability in predicting the tensile strength of the composite material.The research findings indicate that hot extrusion treatment,SiC content,and stirring time have a significant impact on the tensile strength.

Pathogens of first-episode pulmonary infection in 141 children with chronic granulomatous disease

To the Editor:Chronic granulomatous disease(CGD)is an inherited primary immunodeficiency disease characterized by recurrent life-threatening bacterial or fungal infection and tissue granuloma formation.^([1])Pulmonary infection is the most frequent manifestation,affecting nearly 80%of patients,[2]and remains the major cause of morbidity and mortality in patients with CGD.Details of the pathogenic microorganisms responsible for first-episode pulmonary infection provide information on the spectrum of infection in patients with CGD,help guide the empirical choice of antibiotics or antifungal therapy,and contribute to the early identification and management of CGD.Aspergillus is the commonest causative agent of pulmonary infection,but the distribution of other pathogens varies among countries.^([2–5])Few studies have investigated the etiology of pulmonary infection in CGD in a large cohort in China.

Corrosion Behavior of Graphene Nanosheets Reinforced Magnesium Matrix Composites in Simulated Body Fluids

Magnesium(Mg)alloy is considered as a promising biodegradable implant material but restricted to rapid degradation.Here,the new strategies based on thixomolding process had been explored to utilize the outstanding anti-permeability of graphene nanosheets(GNPs)while inhibit its galvanic corrosion with the matrix,so as to improve the corrosion resistance of composites.The agglomerate of GNPs with 0.9 wt%content is the main reason for the deterioration of corrosion performance due to the formation of micro-galvanic corrosion.The grain refinement of composites with 0.6 wt%content had positive effects on the better corrosion resistance.After process adjusting,the unique distributions of GNPs along grain boundaries play a vital role in improving the corrosion resistance.It can be ascribed to the following mechanisms:(I)The barriers can be established between the Mg matrix and corrosive medium,hence blocking the charge transfer at the interface;(II)The GNPs can effectively promote apatite deposition on the Mg matrix,leading to form dense apatite layers and prevent the further invasion of SBF;(III)The GNPs acting as reinforcements exists in the corrosion layer and apatite layer,impede the apatite layer falling off from the Mg matrix.These findings broaden the horizon for biomedical applications in Mg matrix composites to realize desired performances.

Understanding and design of metallic alloys guided by phase-field simulations

Phase-field method(PFM)has become a mainstream computational method for predicting the evolution of nano and mesoscopic microstructures and properties during materials processes.The paper briefly reviews latest progresses in applying PFM to understanding the thermodynamic driving forces and mechanisms underlying microstructure evolution in metallic materials and related processes,including casting,aging,deformation,additive manufacturing,and defects,etc.Focus on designing alloys by integrating PFM with constitutive relations and machine learning.Several examples are presented to demonstrate the potential of integrated PFM in discovering new multi-scale phenomena and high-performance alloys.The article ends with prospects for promising research directions.

Development of Phase-Field Modeling in Materials Science in China:A Review

Phase-field method,as a powerful and popular approach to predict the mesoscale microstructure evolution in various materials science,provides a bridge from atomic-scale methods to the macroscale and has been widely used at an ever-increasing rate.This paper aims to briefly review the origin,basic idea,and development of phase-field models in a historical manner.The focus is placed on the classical and state-of-the-art applications in China,including liquid–solid,solid–solid,gas–solid,ferroelectrics/ferromagnetics phase transformation,and crack propagation-fracture.After introducing the academic activities in the phase-field community in China,some suggestions for the future development directions of phase-field method are finally mentioned.

Coalescence of Al_(0.3)CoCrFeNi polycrystalline high-entropy alloy in hot-pressed sintering: a molecular dynamics and phase- field study

Existing hot sintering models based on molecular dynamics focus on single-crystal alloys.This work proposes a new multiparticle model based on molecular dynamics to investigate coalescence kinetics during the hot-pressed sintering of a polycrystalline Al_(0.3)CoCrFeNi high-entropy alloy.The accuracy and effectiveness of the multiparticle model are verified by a phase-field model.Using this model,it is found that when the particle contact zones undergo pressure-induced evolution into exponential power creep zones,the occurrences of phenomena,such as necking,pore formation/filling,dislocation accumulation/decomposition,and particle rotation/rearrangement are accelerated.Based on tensile test results,Young’s modulus of the as-sintered Al_(0.3)CoCrFeNi high-entropy alloy is calculated to be 214.11±1.03 GPa,which deviates only 0.82%from the experimental value,thus further validating the feasibility and accuracy of the multiparticle model.