喷射沉积成形颗粒增强金属基复合材料制备技术的发展

分析了喷射沉积成形颗粒增强金属基复合材料制备技术的研究现状。系统地介绍了原位反应喷射沉积成形过程中进行的各类反应。在总结国内外喷射沉积成形颗粒增强金属基复合材料制备技术优缺点的基础上,发展了熔铸－原位反应喷射沉积成形金属基复合材料制备新技术。     

喷射共沉积颗粒增强金属基复合材料的研究现状与进展

作为一种综合了铸造与粉末冶金优点制备近成形颗粒增强金属基复合材料的方法,喷射共沉积技术及其应用受到了广泛的关注。本文综述了喷射沉积颗粒增强金属基复合材料的发展现状;介绍了喷射共沉积技术的原理;讨论了喷射共沉积过程中金属液体对增强相的捕获机理和凝固前沿对颗粒的捕获问题;介绍了喷射沉积颗粒增强金属基复合材料的装置及工艺参数的控制;着重介绍了喷射沉积材料的组织性能及致密化工艺,提出通过旋球同步预致密后再分别进行往复镦-挤和等径角挤压实现沉积坯的大塑性变形达到完全致密与冶金结合;指出了喷射沉积金属基复合材料将向组织均匀化、韧性化、完全致密化方向发展。     

雾化喷射沉积制备颗粒增强型金属基复合材料EI

详细地介绍了利用雾化喷射沉积法制备颗粒增强型金属基复合材料的原理、工艺过程以及该方法制备复合材料的优点。另外，指出了目前存在的有待于进一步提高的几个方面。最后，总结了雾化喷射沉积法制备复合材料的发展方向。     

粉末雾化喷射成形制备颗粒增强金属基复合材料

颗粒增强金属基复合材料具有良好的综合，性能在航空、汽车及民用工业中的应用前景十分广阔，近年来粉末雾化喷射成形工艺用于制备颗粒增强ＭＭＣｓ受到了重视与发展，该通过快速凝固获得组织均匀，细小，无宏观偏折和高性能的新材料，在沉积过程中向基体合金的喷雾中喷入增强相颗粒即可制成高性能ＭＭＣｓ，本文介绍这一方法的基本原理和最新进展。     

粉末雾化喷射成形制备颗粒增强金属基复合材料

颗粒增强金属基复合材料（ＭＭＣｓ）具有良好的综合性能，在航空、汽车及民用工业中的应用前景十分广阔。近年来粉末雾化喷射成形工艺用于制备颗粒增强ＭＭＣｓ受到了重视与发展。该方法通过快速凝固获得组织均匀、细小、无宏观偏折和高性能的新材料。在沉积过程中向基体合金的喷雾中喷入增强相颗粒即可制成高性能ＭＭＣｓ。本文介绍这一方法的基本原理和最新进展。     

多层喷射沉积颗粒增强铝基复合材料的研究现状与发展趋势

通过多层喷射沉积技术制备颗粒增强铝基复合材料,强化了冷却效果,能获得细小均匀的显微组织,优化复合材料中增强相的分布及其与基体的结合状态。本文综述了喷射沉积颗粒增强铝基复合材料的发展现状;介绍了多层喷射沉积技术的原理与工艺参数;概述了喷射沉积颗粒增强Al-Zn—Mg系、Al—Fe系与Al-Si系复合材料;并介绍喷射沉积颗粒增强铝基复合材料的致密化技术,着重介绍在小吨位设备上致密大块多孔材料的楔形压制工艺、外框限制轧制、陶粒包覆轧制工艺和热压后轧制工艺;展望了喷射沉积铝基复合材料的的发展趋势,认为增强颗粒与基体界面的结合强度有待进一步提高,提出了多层喷射沉积技术将朝在可编程控制下制备组织均匀、细小且致密度高的大尺寸坯料方向发展,而致密化技术也将朝小吨位设备制备大尺寸致密材料的方向发展,认为热压和楔形压制作为预致密方式能有效提高大尺寸喷射沉积坯料的成形能力,有利于进一步成形。     

选区激光熔化制备颗粒增强金属基复合材料的研究进展

选区激光熔化是一种使用聚焦高能激光束熔化粉末,逐层叠加成形零件的增材制造方法.选区激光熔化可以直接制备复杂结构零件和实现近净成形,能够方便地通过粉末预混添加或原位反应实现颗粒增强金属基复合材料的控形控性,具有独特的技术优势,受到广泛关注.本文综述了选区激光熔化制备颗粒增强金属基复合材料的研究进展,总结了主要研究结果及存在的共性问题,并展望了选区激光熔化制备颗粒增强金属基复合材料的研究方向和发展趋势.通过总结分析,指出选区激光熔化制备颗粒增强金属基复合材料时,聚焦激光作用下形成的高温微小熔池凝固时间短,远远偏离平衡状态,凝固过程复杂,增强颗粒与基体间冶金反应剧烈,容易熔化、分解和溶解并对基体特性产生影响,进而影响成形后的复合材料的宏观形貌和组织、性能.除增强体成分、颗粒形貌与尺寸、体积分数外,复合材料的性能还受激光功率、扫描速度、扫描间距、粉层厚度、成形气氛等工艺参数的影响,粉末特性与工艺参数之间的交互作用复杂.因此,考察工艺参数与粉末特性之间的交互作用关系,系统研究增强体颗粒特性与成形工艺参数对复合材料宏观形貌、致密度、缺陷、组织和性能的影响规律,是实现复合材料组织结构设计和性能调控的基础.     

雾化喷射沉积技术的发展概况及展望

雾化喷射沉积技术是一种新的金属成形工艺，近年来发展十分迅速。本文从实验装置、传热特点、临界沉积条件、沉积材料的组织和性能及主要工业化产品等方面对该工艺进行了综述。并对雾化喷射沉积技术作了评价和展望     

网络陶瓷增强金属复合材料的研究现状

综述了目前网络陶瓷增强金属基复合材料的发展及研究现状,重点介绍了网络陶瓷预制体及复合材料的主要制备工艺,并指出了各工艺的特点.评述了网络陶瓷增强金属复合材料的性能特点,指出了目前网络陶瓷增强金属基复合材料存在的问题及解决方法,并展望了对网络陶瓷增强金属基复合材料未来的发展方向.     

雾化喷射沉积技术的发展概况及展望

雾化喷射沉积技术是一种新的金属成形工艺，近年来发展十分迅速，本文从实验装置、传热特点、临界沉积条件、沉积材料的组织和性能及主要工业化产品等方面对该工艺进行了综述。并对雾化喷射沉积作了评价和展望。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...