Flow characteristics and hot workability of a typical low-alloy high-strength steel during multi-pass deformation

Heavy components of low-alloy high-strength(LAHS) steels are generally formed by multi-pass forging. It is necessary to explore the flow characteristics and hot workability of LAHS steels during the multi-pass forging process, which is beneficial to the formulation of actual processing parameters. In the study, the multi-pass hot compression experiments of a typical LAHS steel are carried out at a wide range of deformation temperatures and strain rates. It is found that the work hardening rate of the experimental material depends on deformation parameters and deformation passes, which is ascribed to the impacts of static and dynamic softening behaviors. A new model is established to describe the flow characteristics at various deformation passes. Compared to the classical Arrhenius model and modified Zerilli and Armstrong model, the newly proposed model shows higher prediction accuracy with a confidence level of 0.98565. Furthermore, the connection between power dissipation efficiency(PDE) and deformation parameters is revealed by analyzing the microstructures. The PDE cannot be utilized to reflect the efficiency of energy dissipation for microstructure evolution during the entire deformation process, but only to assess the efficiency of energy dissipation for microstructure evolution in a specific deformation parameter state.As a result, an integrated processing map is proposed to better study the hot workability of the LAHS steel, which considers the effects of instability factor(IF), PDE, and distribution and size of grains. The optimized processing parameters for the multi-pass deformation process are the deformation parameters of 1223–1318 K and 0.01–0.08 s^(-1). Complete dynamic recrystallization occurs within the optimized processing parameters with an average grain size of 18.36–42.3 μm. This study will guide the optimization of the forging process of heavy components.

Recent progress in visualization and digitization of coherent transformation structures and application in high-strength steel

High-strength steels are mainly composed of medium-or low-temperature microstructures,such as bainite or martensite,with coherent transformation characteristics.This type of microstructure has a high density of dislocations and fine crystallographic structural units,which ease the coordinated matching of high strength,toughness,and plasticity.Meanwhile,given its excellent welding perform-ance,high-strength steel has been widely used in major engineering constructions,such as pipelines,ships,and bridges.However,visual-ization and digitization of the effective units of these coherent transformation structures using traditional methods(optical microscopy and scanning electron microscopy)is difficult due to their complex morphology.Moreover,the establishment of quantitative relationships with macroscopic mechanical properties and key process parameters presents additional difficulty.This article reviews the latest progress in microstructural visualization and digitization of high-strength steel,with a focus on the application of crystallographic methods in the development of high-strength steel plates and welding.We obtained the crystallographic data(Euler angle)of the transformed microstruc-tures through electron back-scattering diffraction and combined them with the calculation of inverse transformation from bainite or martensite to austenite to determine the reconstruction of high-temperature parent austenite and orientation relationship(OR)during con-tinuous cooling transformation.Furthermore,visualization of crystallographic packets,blocks,and variants based on actual OR and digit-ization of various grain boundaries can be effectively completed to establish quantitative relationships with alloy composition and key process parameters,thereby providing reverse design guidance for the development of high-strength steel.

Deep decalcification of factory-provided freezing acidolysis solution to achieveα-high-strength gypsum

The freezing acidolysis solution of the nitric acid-phosphate fertilizer process has a high calcium content,which makes it difficult to produce fine phosphate and high water-soluble phosphate fertilizer products.Here,based on the potential crystallization principle of calcium sulfate in NH_(4)NO_(3)-H_(3)PO_(4)-H_(2)O,the deep decalcification(i.e.calcium removal)technology to achieveα-high-strength gypsum originated from freezing acidolysis-solutions has been firstly proposed and investigated.Typically,calcium can be removed from the factory-provided freezing acidolysis-solution by neutralizing it with ammonia,followed by the addition of ammonium sulfate solution.As a result,the formation of calcium sulfate in the reaction system undergoes the nucleation and growth of CaSO_(4)·2H_(2)O(DH),as well as its dissolution and crystallization into short columnarα-CaSO_(4)·0.5H_(2)O(α-HH).Remarkably,with the molar ratio of SO_(4)^(2-)/Ca^(2+)at 1.8,the degree of neutralization(NH_(3)/HNO_(3) molar ratio)at 1.7,the reaction temperature of 94℃,and the reaction time of 300 min,the decalcification rate can reach 86.89%,of which the high-strengthα-CaSO_(4)·0.5H_(2)O(α-HH)will be obtained.Noteworthy,the deep decalcification product meets the standards for the production of fine phosphates and highly water-soluble phosphate fertilizers.Consequently,the 2 h flexural strength ofα-HH is 5.3 MPa and the dry compressive strength is 36.8 MPa,which is up to the standard of commercialα-HH.

Study on Fracture Delay of High-Strength Bolts in Road Bridge Maintenance

In the maintenance work of highway and bridge engineering structures,the fracture delay of high-strength bolts is a content that needs to be focused on and researched.Based on this,the paper analyzes the fracture delay of high-strength bolts in highway bridge maintenance,including an overview of the fundamental research on fracture delay and related specific studies.It is hoped that this study can provide scientific reference for the reasonable maintenance of high-strength bolts,so as to ensure the overall maintenance effect of highway bridge projects.

Effect of traveling-wave magnetic field on dendrite growth of high-strength steel slab: Industrial trials and numerical simulation

The dendrite growth behavior of high-strength steel during slab continuous casting with a traveling-wave magnetic field was studied in this paper. The morphology of the solidification structure and composition distribution were analyzed. Results showed that the columnar crystals could deflect and break when the traveling-wave magnetic field had low current intensity. With the increase in current intensity, the secondary dendrite arm spacing and solute permeability decreased, and the columnar crystal transformed into an equiaxed crystal. The electromagnetic force caused by the traveling-wave magnetic field changed the temperature gradient and velocity magnitude and promoted the breaking and fusing of dendrites. Dendrite compactness and composition uniformity were arranged in descending order as follows:columnar-toequiaxed transition (high current intensity), columnar crystal zone (low current intensity), columnar-to-equiaxed transition (low current intensity), and equiaxed crystal zone (high current intensity). Verified numerical simulation results combined with the boundary layer theory of solidification front and dendrite breaking–fusing model revealed the dendrite deflection mechanism and growth process. When thermal stress is not considered, and no narrow segment can be found in the dendrite, the velocity magnitude on the solidification front of liquid steel can reach up to 0.041 m/s before the dendrites break.

Hot deformation behavior of novel high-strength Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy

The hot compression behavior of as-extruded Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy was studied on a Gleeble-3500 thermal simulation machine.Experiments were conducted at temperatures ranging from 523 to 673 K and strain rates ranging from 0.001 to 1 s^(-1).Results showed that an increase in the strain rate or a decrease in deformation temperature led to an increase in true stress.The constitutive equation and processing maps of the alloy were obtained and analyzed.The influence of deformation temperatures and strain rates on microstructural evolution and texture was studied with the assistance of electron backscatter diffraction(EBSD).The as-extruded alloy exhibited a bimodal structure that consisted of deformed coarse grains and fine equiaxed recrystallized structures(approximately 1.57μm).The EBSD results of deformed alloy samples revealed that the recrystallization degree and average grain size increased as the deformation temperature increased.By contrast,dislocation density and texture intensity decreased.Compressive texture weakened with the increase in the deformation temperature at the strain rate of 0.01 s-1.Most grains with{0001}planes tilted away from the compression direction(CD)gradually.In addition,when the strain rate decreased,the recrystallization degree and average grain size increased.Meanwhile,the dislocation density decreased.Texture appeared to be insensitive to the strain rate.These findings provide valuable insights into the hot compression behavior,microstructural evolution,and texture changes in the Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy,contributing to the understanding of its processing-microstructure-property relationships.

Development of high-strength magnesium alloys with excellent ignition-proof performance based on the oxidation and ignition mechanisms: A review

High reactivity and ease of ignition are the major obstacles for the application of Mg alloys in aerospace.Thus,the ignition mechanisms of Mg alloys should be investigated systematically,which can guide the ignition-proof alloy design.This article concludes the factors influencing the ignition resistance of Mg alloys from oxide film and substrate microstructure,and also the mechanisms of alloying elements improving the ignition resistance.The low strength is another reason restricting the development of Mg alloys.Therefore,at the last section,Mg alloys with the combination of high strength and good ignition-proof performance are summarized,including Mg-Al-Ca based alloys,SEN(Mg-Al-Zn-Ca-Y)alloys as well as Mg-Y and Mg-Gd based alloys.Besides,the shortages and the future focus of theses alloys are also reviewed.The aim of this article is to promote the understanding of oxidation and ignition mechanisms of Mg alloys and to provide reference for the development of Mg alloys with high strength and excellent ignition-proof performance at the same time.

ZK60 based alloys with high-strength and high-ductility:A review

Wrought magnesium alloys with high-strength and high-ductility property have been attracting more and more interest in automotive and aerospace industries,and the conventional Mg-Zn based alloys are widely accepted as the representative one.Development of Mg-Zn based alloys with rare earth(RE)element additions and with modified preparation processes domains the evolution of their potential structural applications.Nonetheless,their highest tensile yield strength(TYS)is still in the order of 400 MPa,clearly lower than that of the Mg-RE based alloys,in the order of 500 MPa,much less compared with the high-strength aluminum alloys and titanium alloys.According to many previous investigations,two relatively efficient methods to improve mechanical properties of ZK based alloys were revealed as:alloying by RE and optimizing wrought processes.However,comprehensive combinative investigation was hitherto not conducted to date.Thus,it is imperative in the next work to further improve the yield strength to the order of 500 MPa or much higher,and simultaneously modify the tension-compression strength asymmetry of the ZK series alloys.Maybe,developing novel wrought processes for ZK60(+RE)alloys or exploring appropriate pre-dealing treatments before or after the wrought processes might be an important approach to accomplish a much higher level of balance of high-strength and high-ductility.

Microstructure Distribution Characteristics of High-Strength Aluminum Alloy Thin-Walled Tubes during Multi-Passes Hot Power Backward Spinning Process

The microstructure of the thin-walled tubes with high-strength aluminum alloy determines their final forming quality and performance. This type of tube can be manufactured by multi-pass hot power backward spinning process as it can eliminate casting defects, refine microstructure and improve the plasticity of the tube. To analyze the microstructure distribution characteristics of the tube during the spinning process, a 3D coupled thermo-mechanical FE model coupled with the microstructure evolution model of the process was established under the ABAQUS environment. The microstructure evolution characteristics and laws of the tube for the whole spinning process were analyzed. The results show that the dynamic recrystallization is mainly produced in the spinning deformation zone and root area of the tube. In the first pass, the dynamic recrystallization phenomenon is not obvious in the tube. With the pass increasing, the trend of dynamic recrystallization volume percentage gradually increases and extends from the outer surface of the tube to the inner surface. The fine-grained area shows the states of concentration, dispersion, and re-concentration as the pass number increases. .

数字技术赋能下的德化窑瓷雕技艺活化与再生研究

目的 在数字技术赋能下,对德化窑瓷雕技艺进行活化与再生,更好地对德化窑瓷雕技艺进行保护与传承。方法 以德化窑瓷雕技艺为研究对象,将德化窑瓷雕技艺与现有的数字技术手段进行结合,探讨数字技术赋能下的德化窑瓷雕技艺活化与再生的具体内容。首先厘清德化窑瓷雕技艺发展脉络及研究现状,构建研究框架;其次在分析数字化技术在德化窑瓷雕技艺中适用性的基础上,依据德化窑瓷雕技艺保护与传承的特点,有针对性地从数据采集记录、数字知识转化、数字展示传播、数字形态再生四个维度对德化窑瓷雕技艺活化与再生展开具体研究。结论 其为德化窑瓷雕技艺主体及器物客体的数字化保护活化与创新再生增加新的内涵;也为相关非物质文化遗产(特别是传统技艺类项目)的有序传承、科学保护提供理论研究借鉴。

手工艺研究的一些新思考——论非物质文化遗产的物质性与流动性

当前手工艺类非物质文化遗产研究多关注无形文化如技艺习得与技艺传承,容易忽略手工艺发展所依托的有形之物,即物质性基础的研究。人类学整体观视角下将非物质文化遗产作为一个整体,统合了物质与非物质,自然与文化。因此,研究者应对手工艺类非物质文化遗产的物质性与非物质性层面同时进行深度的考察。手工艺类非物质文化遗产作为整体性存在,还包括了流动性与可变性,它并非是凝滞的地方特色产物,其存在与发展始终伴随着与地方社会以外世界的连接与互动。

品牌形象视域下的日用瓷家族化设计策略研究

品牌是企业核心竞争力,产品形象是品牌塑造之基,品牌塑造是产品形象之本。家族化设计是当代产品开发与品牌形象塑造的优化策略,具有传承性、稳定性与差异性特征。家族化设计对于日用瓷设计与品牌形象传播,意义重大。以问题意识为导向,从统一造型符号的设计传承、相似纹样符号的设计延展、个性釉色符号的稳中求变、稳定工艺符号的传承创新四方面,多维度构建日用瓷家族化设计的统一传承符号,并提出日用瓷家族化设计的实现策略。通过日用瓷家族化设计,引发用户日用瓷个性与品牌形象的联想匹配体验,促进日用瓷品牌的高质量发展,实现陶瓷强国的伟大目标。

前牙高透氧化锆全瓷冠修复单颗前牙缺损的美学效果分析

目的:探究高透氧化锆全瓷冠修复单颗前牙缺损的美学效果。方法:选取2018年1月-2020年10月笔者医院收治的单颗前牙缺损患者80例(共80颗患牙),按随机数表法分为观察组(高透氧化锆全瓷冠修复)和对照组(钴铬烤瓷冠修复),每组40例(40颗患牙),比较两组的修复效果,修复前、修复后1个月的牙周指标及龈沟液指标[碱性磷酸酶(Alkaline phosphatase,ALP)、白介素6(Interleukin-6,IL-6)、白介素8(Interleukin-8,IL-8)]水平,对比两组修复后1年的满意度及并发症发生情况。结果:修复后1年,两组颜色对比、边缘着色、解剖外形、边缘密合度、龋齿等修复效果评估观察组均高于对照组(P<0.05)。修复后1个月,两组牙周探诊深度、菌斑指数、出血指数均升高,但观察组低于对照组(均P<0.05);两组龈沟液ALP、IL-6、IL-8水平均降低,且观察组均低于对照组(均P<0.05)。修复后1年,观察组修复总满意度高于对照组(P<0.05);修复后1年期间,两组均未发生牙体腐蚀,疼痛、牙龈炎、根折发生率差异无统计学意义,观察组并发症总发生率低于对照组(P<0.05)。结论:采用高透氧化锆全瓷冠修复单颗前牙缺损的美学效果较好,可减轻牙周组织炎症,值得临床推广应用。

面向青花瓷碎片图像的U-Net++拼接网络

针对现有图像拼接方法存在拼接处伪影以及非重叠区域内容失真,导致较低的准确性和鲁棒性的问题,提出一种基于U-Net++消除伪影的青花瓷碎片图像拼接方法.首先估计待拼接图像单应性矩阵;然后将单应性矩阵应用于结构拼接阶段,得到图像粗拼接结果;最后以图像粗拼接结果作为先验信息,在内容校正阶段改进现有的U-Net,利用U-Net++细化粗拼接结果,得到最终图像精确拼接.以青花瓷碎片图像数据集与相关经典方法进行实验的结果表明,在3个评价指标中,所提方法的峰值信噪比提高约13%,均方根误差降低约33%,均方误差降低57%左右;该方法具有较小的误差比,不仅能够提高图像拼接质量,而且表现出较好的鲁棒性.

汝瓷的艺术特色及数字化展示研究

阐述汝瓷历史发展、艺术特色、工艺细节,分析汝瓷传统展示形式现存的若干问题。将数字化技术运用在汝瓷文化的实体展示空间和新媒体社交平台上,营造沉浸式的观展体验,提高汝瓷数字化展示的文化审美愉悦。

唐代越瓷“秘色”之名出典新考

唐代中后期,越窑生产出不同于以前的精品越瓷,被世人称作“秘色瓷”。根据古籍文献记载,结合近现代考古成果,越窑“秘色瓷”成名实际上有个滥觞至成熟的过程。越窑“秘色瓷”名首次出现在中唐后期,但直到北宋才被大众所接受。“秘色瓷”名源自皇宫,通过文人士大夫向社会传播;窑场所在地始终未见“秘色瓷”名的实物遗存。“秘色”的本质是指器面的釉色。

邢窑六世纪晚期制瓷原料的同位素和微量元素分析

白瓷的出现是我国陶瓷历史上较为重要的技术突破,白瓷的烧制成功为后世青花瓷、彩绘瓷的繁荣奠定了重要基础,被誉为中国古陶瓷工艺发展史中的“第四里程碑”。因此,关于白瓷起源的问题就成为考古界和科技考古界关注的重要学术问题,而邢窑2012年考古发掘出土的北朝晚期窑炉和器物遗存自然成为研究白瓷起源的重要实物资料。本研究利用电感耦合等离子体质谱(ICP-MS)和热电离质谱(TIMS)分析技术,对河北内丘城关服务楼窑址出土的北朝晚期至隋朝初期的早期瓷器样品胎釉原料进行分析,为邢窑早期瓷业的发展演变提供科学依据。结果表明邢窑早期瓷胎的微量元素统计模式明显可以分为两类,说明邢窑早期制瓷存在两种不同的胎料来源。邢窑陶工在开发早期白瓷这一新品种的过程中有意识地选择了一种有别于青瓷的更为优质的原料制胎,这种胎料中与锆石、锐钛矿等杂质赋存密切相关的V、Cr、Ni、Nb、Ta、Zr和Hf等微量元素含量普遍小于青瓷胎。锶(Sr)同位素混合模式分析表明,邢窑早期的大部分样品不符合草木灰配以胎料的制釉方式,应该是采用了草木灰混合其他制釉黏土。同时,早期白瓷釉与青瓷釉的锶同位素特征存在一定差异,说明在制作过程中邢窑陶工为了提高釉面白度对制釉工艺也进行了变革,体现了为创烧早期白瓷而做出的努力。这些结果为科学认知邢窑六世纪晚期制瓷原料的特点和来源提供依据,同时也为破解白瓷起源提供新的科技支撑。

注浆成形制备金尾矿基轻质瓷浆料性能的研究

本研究采用了注浆成形工艺制备金尾矿基轻质瓷制品,研究了其浆料性能。通过引入通过温轮胶、魔芋胶和羟丙基甲基纤维素等悬浮稳定剂来改善陶瓷浆料稳定性和流动性,使浆料达到注浆成形的要求。同时,还阐明了悬浮稳定剂对陶瓷浆料稳定性和流变特性的影响。

明代民窑青花瓷分析

青花瓷作为我国古陶瓷的典型代表之一,受到人们广泛的关注。本文采用SEM、SEM-EDS、XRD等科技手段分析了出自淮安古运河的明代晚期民窑青花瓷碎片坯釉的形貌特征与物相组成。结果表明:釉层中气孔直径较大但较为稀疏,坯体中气孔虽小但较为密集。烧成制度较好的情况下,釉层中残余石英会比坯体中少。釉层相对于坯体Ca含量高、Al含量低,坯体呈现“高硅低铝”特征,属于我国典型的南方陶瓷。明代民窑青花瓷釉层厚度小于0.5mm,且中间层发育完好。明代民窑青花瓷坯体中主要的物相为石英和莫来石,釉层中物相主要以玻璃相的形式存在,其中也含有少量方石英与莫来石分散于玻璃相中。

湖北湖泗浮山窑青白瓷的成分特征研究

湖泗窑是湖北省内唯一的瓷窑,其发现改写了湖北无瓷窑的历史。使用X射线荧光光谱仪对湖泗浮山窑青白瓷的胎釉组成进行检测,探究其胎釉成分特征,并与湖田窑、繁昌窑和定窑已有测试数据进行对比。结果显示:湖泗窑青白瓷胎的Al_(2)O_(3)含量与繁昌窑接近,与湖田窑有明显差异,且远高于当地瓷石的Al_(2)O_(3)含量,据此推测窑工们借鉴了北方窑场的制胎技术,在胎体配方中引入了富铝类黏土;本次所测湖泗浮山窑瓷釉b值介于0.5~0.76,属于钙碱釉,说明早在北宋时期湖泗窑的窑工们就已经对制釉原料的特性有了一定的认识。