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-1during 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 basal(c+a)slip system.©2022 Chongqing University.Publishing services provided by Elsevier B.V.on behalf of Ke Ai Communications Co.Ltd.

Superplastic forming of Ti6Al4V alloy using ZrO_(2)-TiO_(2) ceramic die with adjustable linear thermal expansion coefficient

Firstly,the relation between the coefficient of thermal expansion(CTE)and the volume fraction of TiO_(2) was investigated, and also the influence of relative density of ceramic on the CTE was studied.The results show that the volume fraction of TiO_(2) and the relative density both make influence on the CTE of ZrO_(2)-TiO_(2) ceramic.According to the results,the ZrO_(2)-TiO_(2)(volume fraction of TiO_(2) is 27%)ceramic die with the similar CTE(8.92×10^(-6) ℃^(-1))to Ti6Al4V was fabricated.Secondly,to evaluate the dimensional accuracy of the workpiece superplastically formed,the Ti6Al4V impression experiment was performed.The result shows that the dimensional inaccuracy of workpiece is 0.003.Thirdly,in order to evaluate the practicability,the experiment of superplastic forming Ti6Al4V using ZrO_(2)-TiO_(2) cylinder ceramic die was carried out.The Ti6Al4V cylinder shows good shape retention and surface quality,and high dimensional accuracy.The ceramic dies seem to be adequate for superplastic forming the high accuracy Ti6Al4V, and the trials have confirmed the potential of the ZrO_(2)-TiO_(2) ceramic die.

ANALYSIS OF FORMING PRESSURE AND INSIDE DIAMETER VARIATION IN THIN WALL TUBE PRESS EXPANSION

The forming pressure is calculated by utilizing the slab method and the variation principles and influence factors of inside diameter in thin wall tube press expansion are analyzed.The results of theoretical analysis are well agree with the experiments.The conclusion is valuable to product quality control in the actual manufacturing.

A NEW METHOD FOR ESTABLISHING PSEUDO ORTHOGONAL PROPERTIES OF EIGENFUNCTION EXPANSION FORM IN FRACTURE MECHANICS

A new and simple method is developed to establish the pseudo orthogonal properties (POP) of the eigenfunction expansion form (EEF) of crack-tip stress complex potential functions for cracked anisotropic and piezoelectric materials, respectively. Di?erent from previous research, the complex argument separation technique is not required so that cumbersome manipulations are avoided. Moreover, it is shown, di?erent from the previous research too, that the orthogonal properties of the material characteristic matrices A and B are no longer necessary in obtaining the POP of EEF in cracked piezoelectric materials. Of the greatest signi?cance is that the method presented in this paper can be widely extended to treat many kinds of problems concerning path- independent integrals with multi-variables.

Development and evaluation of a hot-rolled 780 MPa steel sheet with an ultra-high expansion ratio

This paper explores the development of a 780 MPa hot-rolled high-strength steel with an ultra-high hole expansion ratio(HER) by using a nanoprecipitation-controlled technology.Systematic analysis and evaluation of an industrially produced steel sheet have been performed to investigate the microstructure, nanoprecipitates, tensile properties, HER,bendability, and forming limit diagram.The newly developed 780 MPa hot-rolled high-strength steel sheet is composed of a fully ferritic microstructure of approximately 5 μm with precipitates of approximately 4-5 nm in ferrite grain interiors.The yield strength and tensile strength can reach above 700 and 780 MPa, respectively.Moreover, the fractured elongation is higher than 19% in the transversal direction, and the average HER exceeds 70%.Furthermore, the newly developed 780 MPa high-strength steel has good bendability reaching R/t=0.2 at 90°.Compared with the conventional 780 MPa high-strength steel, the newly developed 780 MPa high-strength steel exhibits superior forming ability, which is suitable for the production of complex components.High-cycle fatigue indicates that the fatigue limit of the newly developed high-strength steel is 430 MPa under a stress ratio of r=-1,indicating good fatigue properties.The excellent combined mechanical properties of the newly developed 780 MPa high-strength steel are attributed to the grain-refined ferritic microstructure with nanoprecipitates in ferrite grain interiors.

Relativistic Quantum Mechanical Condition for Expansion of the Universe

In this manuscript, we will discuss about the quantum mechanical system for the movement of non-intractable particle, non-intractable particle which attends every mass state in the universe, the form of a non-intractable particle is n = -m, this manuscript defines the stable cross system for the movement of n-i particles and elementary particles with a perfect black body at centre with proofs of picture of super massive black hole, the linear hamiltonian of the cross quantum mechanical system and with this, it’s co-related matrixes, then by the use of cross system of Non-Intractable Particles defining a new right angel theorem. Then the new black body relation free from plank constant depends on non interactive mechanics and m, which has already mentioned in non-interactive mechanics and it’s relation with galaxies. The unique property of cross system is that it is surrounded by the energy of 10e + e always, and at last the relation between zero point energy and dark energy.

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.

Rational Form Solitary Wave Solutions and Doubly Periodic Wave Solutions to （1＋1）-Dimensional Dispersive Long Wave Equation

In this work we devise an algebraic method to uniformly construct rational form solitary wave solutions and Jacobi and Weierstrass doubly periodic wave solutions of physical interest for nonlinear evolution equations. With the aid of symbolic computation, we apply the proposed method to solving the (1+1)-dimensional dispersive long wave equation and explicitly construct a series of exact solutions which include the rational form solitary wave solutions and elliptic doubly periodic wave solutions as special cases.

Forming regularity and relation between composition and property of B_2O_3-BaO-ZnO glass

B2O3-BaO-ZnO glass was prepared by using conventional melt quenching technology. The forming regularity and the relationship between the composition and the property of B2O3BaOZnO glass were investigated. The results show that the composition range for forming B2O3BaOZnO glass is very wide, but the content of B2O3 has a limit within mole fraction of 25%75%. When the content of B2O3 is over the limit, the melt will be divided into two phases with different compositions and structures, whereas too low content of B2O3 will result in the crystallization of the melt during the cooling process. The thermal expansion coefficient, the transition temperature and the resistivity of the glass at room temperature are （510）×10 -6℃ -1, 480620℃ and （1.53.0）×10 10Ω·m, respectively.

RESEARCH ON HYDROFORMING TUBULAR PART WITH LARGE PERIMETER DIFFERENCE

The tube hydro forming process for manufacturing the tubular part with large perimeter difference was studied by means of experiments and FE simulation. It is an asymmetrical one and the expansion ratio is 70 percent. The part is successfully hydro formed by applying the useful wrinkles to accumulate sufficient metal in the area with large expansion ratio. The thickness distribution is analyzed, and the maximum thinning ratio of the part is 21.6 percent. It is shown from the experiment and simulation results that the tubular part with large perimeter difference, long expansion area and asymmetrical shape can be obtained in one step, applying the useful wrinkles. Typical failure modes were analyzed.

Property measurements on spray formed Si-Al alloys

A novel Si-Al alloy was prepared by spray forming process for electronic packaging. Property measurements on spray-formed Si-Al alloys after hot pressing were carried out. The results indicate that the alloys (Si-(30%-40%)Al) have advantageous physical and mechanical characteristics, including low coefficient of thermal expansion (6.9×10-6-8.7×10-6/K), high thermal conductivity (118-127 W/(m·K)), low density (2.421×103-2.465×103 kg/m3), high ultimate flexural strength (180-220 MPa) and Brinell hardness (162261). The alloys are easy to machine to tight tolerances using standard machine tools and they can be electroplated with gold finishes and soldered with Sn-Pb alloy without any difficulty.

New Families of Rational Form Solitary Wave Solutions to （2＋1）-Dimensional Broer-Kaup-Kupershmidt System＊

Taking the (2+1)-dimensional Broer-Kaup-Kupershmidt system as a simple example, some families of rational form solitary wave solutions, triangular periodic wave solutions, and rational wave solutions are constructed by using the Riccati equation rational expansion method presented by us. The method can also be applied to solve more nonlinear partial differential equation or equations.

资本扩张的内涵、边界与常态化监管

资本具有自然形态和社会形态双重属性,自然属性主要体现资本要素作用,社会属性更多体现特定的社会生产关系。资本扩张是资本自然形态和社会形态辩证统一、相互交织的过程,具有市场型扩张、资源型扩张、牌照型扩张等三个基本模式。由于趋利性,资本存在多样化无序扩张现象,在微观和宏观层面可能存在侵害中小投资者权益、弱化监管系统有效性等多重威胁。资本监管要充分认识资本的双重属性,将“两个毫不动摇”作为资本监管的基本原则,充分尊重资本正向价值,覆盖资本扩张所有环节,重点防范资本无序扩张的潜在风险,特别是系统性金融风险和数字经济潜在的新型金融风险。资本监管要健全资本监管长效机制,深化资本监管法治建设,着重加强机构公司治理,有效统筹资本双重属性,着力提升生产力,注重优化生产关系,不断强化为中国式现代化服务的功能。

CONTROLLED HOT FORMING OF RETAINING RING OF GENERATOR

The relevant results of thermodynamics simulation test, recrystallization study and FEM numercal simulation are described. A method is also introduced that the controlled hot forming is carried out by adopting the program of expansion-extrusion compound forming.

以消费扩容提质促进经济高质量发展的理论逻辑及政策取向

在中国经济由高速增长转向高质量发展的新阶段,国内需求结构发生变迁,消费不断扩容提质,成为中国经济高质量发展的新动能,其理论逻辑是:消费规模扩大能够加快经济增长和经济循环,消费结构升级能够优化经济结构,新型消费的产生能够提升民生福祉。然而,中国消费在总量扩大、结构优化和质量提升方面还面临一些限制性因素,主要表现在:宏观经济增长不足制约居民收入提升,服务业发展滞后导致服务消费占比偏低,社会保障不足抑制中低收入群体消费潜力释放,体制机制和配套设施不够完善致使新型消费扩容受限。应从保持居民收入与宏观经济基本同步增长、加快服务业供给侧结构性改革、强化社会保障功能、加强新型消费的软硬环境建设等方面,构建消费扩容提质长效机制,让消费作为主动能更好促进经济高质量发展。

喷头流道结构参数对高黏度含能材料直写成型3D打印挤出过程稳定性影响

为了研究直写成型技术(DIW)中挤出系统的喷头流道结构参数(锥角角度、出口直径、成型段长度)对含能材料挤出过程的流体流动影响,研究建立了基于Polyfow Extrusion模块的高黏度含能材料挤出模型,并采用直写成型3D打印工况的挤出实验对其进行了验证。研究通过所建立的模型分析了锥角角度范围90°~130°,出口直径0.75~2 mm以及成型段长度5~20 mm对高黏度含能材料挤出过程的影响。结果表明:采用Polyflow Extrusion模块可以较准确地模拟复合含能材料的流动行为,同时发现锥角为100°、喷头出口直径为1.5~1.75 mm时挤出成型过程相对稳定、挤出膨胀较小,且成型段的增长会在增大所需入口压强的同时减小出口膨胀效应。

模具材料线胀系数对复合材料固化变形的影响研究

为了研究模具材料线胀系数对复合材料固化变形的影响,面向复合材料零件热压罐固化成形工艺过程,针对复合材料成形模具材料与复合材料零件线胀系数不一致导致复合材料零件热固化变形的问题,研究了模具与复合材料零件相互作用关系,推导了模具对复合材料固化变形的理论模型,利用ABAQUS等仿真软件建立了模具温度场的数值模拟模型,并将模具热变形的模拟数据与复合材料零件变形的试验数据进行了对比分析。结果表明,不同材料模具型面各位置变形值与型面结构特征无关,与型面大小有关;模具材料与复合材料的线胀系数差异越大,复合材料零件变形量越大。

Usibor■2000热成形钢胀形性能研究

基于H1F-60伺服压力机及配套冲压成形测试系统,对Usibor■2000热成形钢冷热胀形性能进行了系统研究。试验结果表明,随着压边力和冲压速度的增加,材料的杯突IE值先增大后减小。当压边力为10 kN时,IE值达到了9.45 mm;在冲压速度为40 mm·s^(-1)时,IE值达到了9.26 mm,相较于最小值提高了约6%。随着温度的升高,板料胀形性能逐渐降低。但850℃胀形后板料硬度达到458 HV,较原始板料提高了85%。采用Autoform软件进行胀形模拟,模拟结果与试验结果呈现出一致的趋势。观察发现,在高温下断口较为平整,且板料厚度减薄明显。室温下的晶粒拉伸现象验证了板料优良的胀形性能;而温度升高到再结晶温度以上时形成了细化的等轴晶组织。

贵南高铁南宁段古近系泥岩膨胀性判别指标适用性分析

贵南高铁南宁段古近系泥岩是湖沼沉积型半成泥岩,易遇水软化,失水崩解,有一定胀缩性。依托贵南高铁南宁段泥岩样品膨胀性试验数据及路堑边坡人字型骨架开裂的实际现象,采用了相关性、线性回归、匹配度等分析方法,对膨胀性判别指标适用性进行了研究。研究结果表明,干燥饱和吸水率单指标膨胀潜势分级结果与实际较接近,天然湿度样品的膨胀力、交换阳离子含量、蒙脱石含量及自由膨胀率等单指标膨胀潜势分级结果易下降1–2个等级。

基于星点设计和响应面法的支架焊合件成形工艺优化

通过对焊合件的材料、结构及工艺进行分析,确定关键影响工序。对原冲压工艺方案进行多工序仿真模拟,并分析仿真结果,找寻产生开裂缺陷的原因。通过增加焊合件预成形设计和改变坯料的形状来改善工序间的载荷传递,建立以焊合件的最大减薄率和最大回弹量为优化目标,以冲压速度、摩擦因数、压边力和模具间隙为设计变量的响应面模型,结合二阶响应面法与DesignExpert,采用星点设计试验方法对支架焊合件的工艺参数进行优化,确定最佳参数组合为:冲压速度1263mm·s^(-1)、摩擦因数0.15、压边力598k N、模具间隙4.55mm。试产结果表明:通过预成形方案与优化工艺参数可以解决支架焊合件开裂及回弹问题。