Microstructure and forming mechanism of metals subjected to ultrasonic vibration plastic forming: A mini review

Compared with traditional plastic forming,ultrasonic vibration plastic forming has the advantages of reducing the forming force and improving the surface quality of the workpiece.This technology has a very broad application prospect in industrial manufactur-ing.Researchers have conducted extensive research on the ultrasonic vibration plastic forming of metals and laid a deep foundation for the development of this field.In this review,metals were classified according to their crystal structures.The effects of ultrasonic vibration on the microstructure of face-centered cubic,body-centered cubic,and hexagonal close-packed metals during plastic forming and the mech-anism underlying ultrasonic vibration forming were reviewed.The main challenges and future research direction of the ultrasonic vibra-tion plastic forming of metals were also discussed.

Deformation mechanisms and microstructural characteristics of AZ61 magnesium alloys processed by a continuous expansion extrusion approach

The unique continuous extrusion-based severe plastic deformation approaches were proposed recently to process high-performance magnesium(Mg)alloys,while the in-depth deformation mechanisms under such complicated thermomechanical conditions were not well understood.In the present work,the fundamental deformation behaviors of AZ61 Mg alloy from 25 to 400°C were firstly examined under uniaxial compression deformation.Then the deformation mechanisms and microstructural characteristics of AZ61 Mg alloy during continuous expansion extrusion forming(CEEF)were systematically investigated by microstructural observations,finite element and cellular automata simulations.The results showed that the continuous evolutions of temperature,larger strain level and complex stress state with strain rate range of 0∼5.98 s−1 during CEEF brought the distinctive dynamic recrystallization behaviors and texture development in AZ61 Mg alloy,which were different to that of uniaxial compression deformation.In details,a remarkable grain refinement was achieved via CEEF processing due to the simultaneous actions of continuous dynamic recrystallization(CDRX)and discontinuous dynamic recrystallization(DDRX).Gradually enhanced CDRX were observed from center to edge region,which had significant effects on the texture distribution and texture strength.The c-axis of most grains rotated under distinctive shear strain following parabolic metal flow,resulting in stable fiber texture.In addition,the evolution of the internal texture of the alloy led to an obvious increase in the Schmid factor for the activation of basalc+aslip system.©2022 Chongqing University.Publishing services provided by Elsevier B.V.on behalf of KeAi Communications Co.Ltd.

MPI/OpenMP-Based Parallel Solver for Imprint Forming Simulation

In this research,we present the pure open multi-processing(OpenMP),pure message passing interface(MPI),and hybrid MPI/OpenMP parallel solvers within the dynamic explicit central difference algorithm for the coining process to address the challenge of capturing fine relief features of approximately 50 microns.Achieving such precision demands the utilization of at least 7 million tetrahedron elements,surpassing the capabilities of traditional serial programs previously developed.To mitigate data races when calculating internal forces,intermediate arrays are introduced within the OpenMP directive.This helps ensure proper synchronization and avoid conflicts during parallel execution.Additionally,in the MPI implementation,the coins are partitioned into the desired number of regions.This division allows for efficient distribution of computational tasks across multiple processes.Numerical simulation examples are conducted to compare the three solvers with serial programs,evaluating correctness,acceleration ratio,and parallel efficiency.The results reveal a relative error of approximately 0.3%in forming force among the parallel and serial solvers,while the predicted insufficient material zones align with experimental observations.Additionally,speedup ratio and parallel efficiency are assessed for the coining process simulation.The pureMPI parallel solver achieves a maximum acceleration of 9.5 on a single computer(utilizing 12 cores)and the hybrid solver exhibits a speedup ratio of 136 in a cluster(using 6 compute nodes and 12 cores per compute node),showing the strong scalability of the hybrid MPI/OpenMP programming model.This approach effectively meets the simulation requirements for commemorative coins with intricate relief patterns.

Effect of Low pH on Forming Process of Desulfurization Gypsum Composite Boards Strengthened by Melamine-formaldehyde Resin

Through exploring the effects of low pH on the composite system of desulfurization gypsum(DG)enhanced by melamine-formaldehyde resin(MF),it is found that the inducing of sulfate-ion,in contrast to chloride and oxalate ions,favors the longitudinal growth of the crystalline form of the hydration product,which was relatively simple and had the highest length to width(L/D)ratio.At the same time,MF can also improve L/D ratio of gypsum hydration products,which favors the formation of hydrated whiskers.Finally,in a composite system composed of hemihydrate gypsum,MF,and glass fibers,when dilute sulfuric acid was used to regulate pH=3-4,the tight binding formed among the components of the composite system compared to pH=5-6.The hydration product of gypsum adheres tightly to glass fiber surface and produces a good cross-linking and binding effect with MF.The flexural strength,compressive strength,elastic modulus,and water absorption of the desulphurized gypsum composite board is 22.7 MPa,39.8 MPa,5608 MPa,and 1.8%,respectively.

Method of fabricating artificial rock specimens based on extrusion free forming(EFF)3D printing

Three-dimensional(3D)printing technology has been widely used to create artificial rock samples in rock mechanics.While 3D printing can create complex fractures,the material still lacks sufficient similarity to natural rock.Extrusion free forming(EFF)is a 3D printing technique that uses clay as the printing material and cures the specimens through high-temperature sintering.In this study,we attempted to use the EFF technology to fabricate artificial rock specimens.The results show the physico-mechanical properties of the specimens are significantly affected by the sintering temperature,while the nozzle diameter and layer thickness also have a certain impact.The specimens are primarily composed of SiO_(2),with mineral compositions similar to that of natural rocks.The density,uniaxial compressive strength(UCS),elastic modulus,and tensile strength of the printed specimens fall in the range of 1.65–2.54 g/cm3,16.46–50.49 MPa,2.17–13.35 GPa,and 0.82–17.18 MPa,respectively.It is capable of simulating different types of rocks,especially mudstone,sandstone,limestone,and gneiss.However,the simulation of hard rocks with UCS exceeding 50 MPa still requires validation.

Effect of cold rolling deformation on microstructure evolution and mechanical properties of spray formed Al−Zn−Mg−Cu−Cr alloys

The impact of cold rolling deformation,which was introduced after solid solution and before aging treatment,on microstructure evolution and mechanical properties of the as-extruded spray formed Al−9.8Zn−2.3Mg−1.73Cu−0.13Cr(wt.%)alloy,was investigated.SEM,TEM,and EBSD were used to analyze the microstructures,and tensile tests were conducted to assess mechanical properties.The results indicate that the D1-T6 sample,subjected to 25%cold rolling deformation,exhibits finer grains(3.35μm)compared to the D0-T6 sample(grain size of 4.23μm)without cold rolling.Cold rolling refines the grains that grow in solution treatment.Due to the combined effects of finer and more dispersed precipitates,higher dislocation density and smaller grains,the yield strength and ultimate tensile strength of the D1-T6 sample can reach 663 and 737 MPa,respectively.In comparison to the as-extruded and D0-T6 samples,the yield strength of the D1-T6 sample increases by 415 and 92 MPa,respectively.

A Hybrid Optimization Approach of Single Point Incremental Sheet Forming of AISI 316L Stainless Steel Using Grey Relation Analysis Coupled with Principal Component Analysiss

We investigated the parametric optimization on incremental sheet forming of stainless steel using Grey Relational Analysis(GRA) coupled with Principal Component Analysis(PCA). AISI 316L stainless steel sheets were used to develop double wall angle pyramid with aid of tungsten carbide tool. GRA coupled with PCA was used to plan the experiment conditions. Control factors such as Tool Diameter(TD), Step Depth(SD), Bottom Wall Angle(BWA), Feed Rate(FR) and Spindle Speed(SS) on Top Wall Angle(TWA) and Top Wall Angle Surface Roughness(TWASR) have been studied. Wall angle increases with increasing tool diameter due to large contact area between tool and workpiece. As the step depth, feed rate and spindle speed increase,TWASR decreases with increasing tool diameter. As the step depth increasing, the hydrostatic stress is raised causing severe cracks in the deformed surface. Hence it was concluded that the proposed hybrid method was suitable for optimizing the factors and response.

Analysis and Optimization of the Electrohydraulic Forming Process of Sinusoidal Corrugation Tubes

Aluminum alloy thin-walled structures are widely used in the automotive industry due to their advantages related to light weight and crashworthiness.They can be produced at room temperature by the electrohydraulic forming process.In the present study,the influence of the related parameters on the forming quality of a 6063 aluminum alloy sinusoidal corrugation tube has been assessed.In particular,the orthogonal experimental design(OED)and central composite design(CCD)methods have been used.Through the range analysis and variance analysis of the experimental data,the influence degree of wire diameter(WD)and discharge energy(DE)on the forming quality was determined.Multiple regression analysis was performed using the response surface methodology.A prediction model for the attaching-die state coefficient was established accordingly.The following optimal arrangement of parameters was obtained(WD=0.759 mm,DE=2.926 kJ).The attaching-die state coefficient reached the peak value of 0.001.Better optimized wire diameter and discharge energy for a better attaching-die state could be screened by CCD compared with OED.The response surface method in CCD was more suitable for the design and optimization of the considered process parameters.

Design and characterization of biodegradable Mg-Zn-Ag metallic glasses

In order to develop the Mg-Zn-Ag metallic glasses(MGs)for biodegradable implant applications,the glass formation ability(GFA)and biocompatibility of Mg-Zn-Ag alloys were investigated using a combination of the calculation of phase diagrams(CALPHAD)and experimental measurements.High GFA potentiality of two alloy series,specifically Mg_(96-x)Zn_xAg_(4)and Mg_(94-x)Zn_xAg_6(x=17,20,23,26,29,32,35),was predicted theoretically and then substantiated through experimental testing.X-ray diffraction(XRD)and differential scanning calorimetry(DSC)techniques were used to evaluate the crystallinity,GFA,and crystallization characteristics of these alloys.The results showed that compositions between Mg_(73)Zn_(23)Ag_(4)and Mg_(64)Zn_(32)Ag_(4)for Mg_(96-x)Zn_xAg_4,Mg_(66)Zn_(28)Ag_(6)and Mg_(63)Zn_(31)Ag_(6for)Mg_(94-x)Zn_xAg_(6)displayed a superior GFA.Notably,the GFA of the Mg_(96-x)Zn_xAg_(4)series was better than that of the Mg_(94-x)Zn_xAg_(6)series.Furthermore,the Mg_(70)Zn_(26)Ag_4,Mg_(74)Zn_(20)Ag_6,and Mg_(71)Zn_(23)Ag_(6)alloys showed acceptable corrosion rates,good cytocompatibility,and positive effects on cell proliferation.These characteristics make them suitable for applications in medical settings,potentially materials as biodegradable implants.

Study on the Mechanism of Nanopatterning in Printed Electronics Based on Molecular Dynamics Simulation

In order to research the feasibility of using the selective adsorption principle to achieve automatic shaping of nano patterns,in this study,using the liquid gallium as the conductive ink and graphene as the printing plate surface,by changing the surface wettability of patterned areas on the nanoscale of graphene printed boards,the automatic formation of liquid gallium patterns on the graphene printed plate surface was simulated.The results indicated that liquid gallium can achieve automatic patterning on the surface of graphene patterned areas;the greater the interaction energy between gallium and carbon atoms,the clearer the pattern;gallium liquid is prone to remain in complex local positions of the pattern,making it difficult to shape the pattern;if the spacing between adjacent pattern lines is too large or too small,it will result in residual gallium liquid between the lines;increasing the thickness of the gallium film will cause the pattern to expand beyond the boundary,but increasing the thickness of the gallium film can also enhance the thickness and uniformity of the pattern lines.In summary,the principle of selective adsorption can be used to achieve the automatic formation of nano patterns,and the pattern formation effect is influenced by factors such as atomic interaction energy and pattern configuration.

Optimization of short-circuit transition parameters of Q235B steel GMAW based on orthogonal gray relational analysis

In gas metal arc welding(GMAW)process,the short-circuit transition was the most typical transition observed in molten metal droplets.This paper used orthogonal tests to explore the coupling effect law of welding process parameters on the quality of weld forming under short-circuit transition,the design of 3 factors and 3 levels of a total of 9 groups of orthogonal tests,welding current,welding voltage,welding speed as input parameters:effective area ratio,humps,actual linear power density,aspect ratio,Vickers hardness as output paramet-ers(response targets).Using range analysis and trend charts,we can visually depict the relationship between input parameters and a single output parameter,ultimately determining the optimal process parameters that impact the single output index.Then combined with gray the-ory to transform the three response targets into a single gray relational grade(GRG)for analysis,the optimal combination of the weld mor-phology parameters as follows:welding current 100 A,welding voltage 25 V,welding speed 30 cm/min.Finally,validation experiments were conducted,and the results showed that the error between the gray relational grade and the predicted value was 2.74%.It was observed that the effective area ratio of the response target significantly improved,validating the reliability of the orthogonal gray relational method.

Experimental study on the forming characteristics of 1.5 GPa ultrahigh-strength dual-phase steel

The DP1500 steel series successfully produced by Baosteel is a marked improvement over the cold-rolled hot-dip galvanized dual-phase steel series.Sufficient parameter data related to forming characteristics are needed for the successful application of dual-phase steel series in engineering structures.Therefore,differences in the mech-anical properties,forming limit,hole expansion ratio,and stretch bend limit of the 1.5 GPa ultrahigh-strength steel,including DP1500,QP1500,and MS1500,have been systematically studied.Results show that the DP1500 exhibits good plastic deformation performance and approximately 5% uniform elongation,and its true major strain minimum on the forming limit curve(FLC_(0)) value is approximately 0.083,which is higher and lower than the FLC_(0) values of MS1500 and QP1500 of the same strength grade,respectively.DP1500 also exhibits good flanging and pore expansion capabilities and superior performance to QP1500 and MS1500.The minimum radius-to-thickness(R/T) ratio(1.4) of DP1500 in the 90° bend tests transverse to the rolling direction is between the R/T ratios of MS1500 and the QP1500.Overall,the formability performance of DP1500 is between that of MS1500 and QP1500.Its excellent crash energy absorption and formability performance render it a suitable structural component,and it has been successfully tested and verified on a typical complex ultrahigh-strength steel skeleton structure.

The Pairing Analysis Improvement of Magnetized Structure in Electromagnetic Bulging Process in Case of Tube with Field Shaper

In the current practical science, the accuracy in the formability of metal alloys being the goal when using electromagnetic forming (EMF) technology, which is a high-speed processing technology that uses Lorentz forces to achieve plastic deformation of sheet metal;according to the previous analysis, the results have shown that in most cases, the Lorentz force acting on the workpiece (metal) is not uniform, there are uneven axial deformations of the metal plates which prevent the rapid advancement of today’s technology. In this article, we presented some advanced analyzes which will lead us to improve the technical solution for the problems of non-uniform axial deformations of the metals in the traditional tube electromagnetic forming technology (EMF). A field shaper is used as a practical forming tool to influence the magnetic field and magnetic pressure distribution, thereby improving the forming ability and result during the electromagnetic forming (EMF) process and we see that induced eddy current control is realized by changing the structural parameters of the magnetic field shaper;which improves the strength and controllability of the magnetic force that acts on the workpiece;thereby a greater radial magnetic pressure can be achieved with field shaper than the case without it;the field shaper regulates the electromagnetic force, the distribution of the magnetic pressure decreases, and the uniform force area of the tube increases which effectively enhances the uniform range of the pipe electromagnetic bulging and the electromagnetic induction coupling between the coil and the metallic workpiece is generally required to produce the Lorentz forces. Using COMSOL Multiphysics® simulation software helped us to accurately represent the real world, simulating multiple physical effects that happened in this model during the process.

Analysis of the Haze Weather Process in the East of China from January 21 to 28, 2021

Haze is a pollution weather phenomenon that has been widely concerned by people in recent years. It has a significant impact on people’s production, life, and health. This study focuses on large-scale haze weather that happened in eastern China in late January 2021. The research uses multi-party data and synoptic analysis methods to analyze the occurrence, evolution, and end of the haze weather. The polar vortex, the change of the atmospheric circulation, the change of the cold air force, the temperature and humidity, and the rain and snow weather are the important reasons for this weathering process. It can be used for reference in future research on haze weather.

Additive manufacturing of magnesium and its alloys: process-formabilitymicrostructure-performance relationship and underlying mechanism

Magnesium and its alloys,as a promising class of materials,is popular in lightweight application and biomedical implants due to their low density and good biocompatibility.Additive manufacturing(AM)of Mg and its alloys is of growing interest in academia and industry.The domain-by-domain localized forming characteristics of AM leads to unique microstructures and performances of AM-process Mg and its alloys,which are different from those of traditionally manufactured counterparts.However,the intrinsic mechanisms still remain unclear and need to be in-depth explored.Therefore,this work aims to discuss and analyze the possible underlying mechanisms regarding defect appearance and elimination,microstructure formation and evolution,and performance improvement,based on presenting a comprehensive and systematic review on the relationship between process parameters,forming quality,microstructure characteristics and resultant performances.Lastly,some key perspectives requiring focus for further progression are highlighted to promote development of AM-processed Mg and its alloys and accelerate their industrialization.

基于PSO-BP神经网络的双相不锈钢电弧增材制造焊道成形预测

Duplex stainless steel was formed through welding wire and arc additive manufacturing(WAAM)using tungsten inert gas.The effects of wire feeding speed(WFS),welding speed(WS),welding current,and their interaction on the weld bead width and height were discussed.Back-propagation(BP)neural network algorithm prediction model was established by taking the bead width and height as the output layer,and the network weight and threshold values were optimized using the particle swarm optimization(PSO)algorithm to obtain the prediction model of bead width and height.The predicted results were verified by experiments.Results show that the weld bead width increases with the increase in WFS and the welding current and decreases with WS.The smaller the WFS,the faster the WS,which is beneficial for the generation of equiaxed crystals.The smaller the welding current,the faster the cooling speed of the metal melt,which is conducive to the formation of dendrites.The interaction among WS,wire feed speed,and welding current has a significant effect on the bead width.The weld bead height is positively correlated with the wire feed speed and negatively correlated with the WS and current.The interaction between the wire feed speed and WS is significant.The optimized WAAM process parameters for duplex stainless steel are a wire feed speed of 200 cm/min,WS of 24 cm/min,and welding current of 160 A.The maximum error of the BP neural network in predicting the weld bead width and height is 7.74%,and the maximum error between the predicted and experimental values of the BP-PSO neural network is 4.27%.This finding indicates that the convergence speed is fast,improving the prediction accuracy.

Recent research and development on forming for large magnesium alloy components with high mechanical properties

The lightweight of high-end equipment relies on high mechanical properties magnesium(Mg) alloy structural components, because it is the best way to improve equipment service performance and reduce energy consumption. This article summarizes the current progress and characteristics of large-scale high-performance Mg alloy components by analyzing the strengthening-toughening mechanisms, characteristics of plastic forming, and the preparation of large high mechanical properties forging blanks. Due to the lack of breakthroughs in the key technologies for forming large-scale Mg alloy components, their uniformity of mechanical properties and consistency are poor, the forming accuracy of components is low, and the production cost is high, which limit their engineering application and restrict the lightweight level of high-end equipment. In view of the above problems, the forming trends and research directions of large-scale and high mechanical properties Mg alloy components are proposed in this paper. It can provide help for the breakthrough of the key technology of large-scale Mg alloy components with high mechanical properties and expand the application of Mg alloy in high-end products.

Local Buckling-Induced Forming Method to Produce Metal Bellows

A novel buckling-induced forming method is proposed to produce metal bellows.The tube billet is firstly treated by local heating and cooling,and the axial loading is applied on both ends of the tube,then the buckling occurs at the designated position and forms a convolution.In this paper,a forming apparatus is designed and developed to produce both discontinuous and continuous bellows of 304 stainless steel,and their characteristics are discussed respectively.Furthermore,the influences of process parameters and geometric parameters on the final convolution profile are deeply studied based on FEM analysis.The results suggest that the steel bellows fabricated by the presented buckling-induced forming method have a uniform shape and no obvious reduction of wall thickness.Meanwhile,the forming force required in the process is quite small.

Genesis of Pyroxenite Veins in the Zedang Ophiolite,Southern Tibetan Plateau

Understanding the nature of parental melts for pyroxenite veins in supra-subduction zone(SSZ)ophiolites provides vibrant constraints on melt infiltration processes operating in subduction zones.The Zedang ophiolitic massif in the eastern Yarlung–Zangbo suture zone in Tibet consists of mantle peridotites and a crustal section of gabbro,diabase,and basalt.Veins of two pyroxenite varieties cut the southern part of the Zedang massif.These pyroxenite rocks have different geochemical characteristics,where the first variety(type-I)has relatively higher contents of SiO_(2)(51.82–53.08 wt%),MgO(20.08–23.23 wt%),andΣPGE(3.42–13.97 ppb),and lower Al_(2)O_(3)(1.59–2.28 wt%)andΣREE(1.63–2.94 ppm).The second pyroxenite variety(type-II)is characterized by SiO_(2)(45.44–49.61 wt%),Mg O(16.68–19.78 wt%),Al_(2)O_(3)(4.24–8.77 wt%),ΣPGE(14.46–322.06 ppb),andΣREE(5.82–7.44 ppm).Pyroxenite type-I shows N-MORB-like chondritenormalized REE patterns.Zircon U-Pb ages of pyroxenite type-I(194±10 Ma),associated ophiolitic gabbro(135.3±2.0 Ma),and plagiogranite(124.2±2.3 Ma)evidently imply episodic evolution of the Zedang ophiolites.The mineralogical and geochemical characteristics of the investigated pyroxenites can be explained by subduction-initiated hydrous melting of metasomatized sub-arc mantle,later overprinted by sub-slab mantle melting triggered by upwelling asthenosphere during the Jurassic–Early Cretaceous times.The geochemical variations in pyroxenite vein composition,coupled with age differences amongst the other ophiolite units,may correspond to intermittent emplacement of pyroxenite dikes and isotropic gabbroic intrusions where the geodynamic setting progressed from arc maturation and slab rollback to slab tearing and delamination.

电化学金属化阻性存储器导电细丝生长中的离子动力学研究

以Arrhenius定律和电化学金属化器件中离子运动的超势理论作为离子运动的基础,本文建立了修正的Mott-Gurney微分方程组.虽然Mott-Gurney方程没有解析解,但采用该方程可求出离子的平均位移.再通过基于Cell的几何模型,求出平均位移与导电细丝生长长度的关系.得到电压与Forming/Set时间方程和导电细丝生长方程.本文提出了一个提取离子的动力学参数的算法,采用该算法计算了Ag/γ-AgI/Pt,Ag/TiO_(2)/Pt,Ag/GeS_(2)/W和Cu/SiO_(2)/Au四种器件的电压-Forming/Set时间特性,其计算结果与实验数据一致.计算结果表明Ag^(+)离子在单晶电介质γ-AgI,TiO_(2)和GeS_(2)中的跃迁步长是晶胞的某一个晶格常数,而Ag离子在无定形SiO_(2)的跃迁步长是O—O键的1.57倍.导电细丝生长时,Ag^(+)离子在γ-AgI和TiO_(2)中的导电隧道是间隙隧道,而在GeS_(2)和SiO_(2)中也存在阳离子的导电隧道,这些导电隧道可以用周期势垒表示.还计算了这4种器件的离子激活频率、势垒高度、迁移率、扩散系数和导电细丝生长长度与时间特性,讨论了ECM器件电介质材料选择的标准.