航空航天领域常用高温钎料研究现状

近年来随着航空航天工业的发展,各类飞行器核心功能部件面临着使役环境愈发极端化的问题。超高速、高温等服役环境对各类零部件的整体性能提出了更高的要求,因此针对航空航天领域用高温钎料的研究尤为重要。在航空航天领域常用的高温钎料包括镍基钎料、钴基钎料、钛基钎料、锰基钎料、贵金属钎料和高熵钎料等,通常应用于不锈钢、高温合金、钛合金以及新型陶瓷材料等的钎焊连接。主要针对在航空航天领域中常用的几种高温钎料,对钎料的元素组成和特性进行总结,对钎料的成形特点和工艺进行介绍,对研究和应用现状进行分析,并对航空航天领域的钎料与钎焊技术提出建议与展望,以期为提升钎焊技术在航空航天领域的应用价值提供参考和指导。     

高熵合金在钎焊和表面工程领域的应用研究进展

随着合金制造水平的提高及性能要求的复杂化,高熵合金逐渐引起极大的关注.目前在材料加工领域内的研究主要集中于钎焊和表面工程两大方向.在钎焊领域,高熵合金可以作为钎焊填充材料应用于高温和低温钎焊,本文归纳了合金高熵化的相关经验参数,阐述了第一性原理计算和相图计算等模拟计算手段在高熵合金填充材料设计领域内的应用;详细介绍了高熵合金钎料在镍基高温合金、陶瓷-金属异种材料、低温封装等连接领域的最新研究进展.同时,分析了工艺参数对高熵合金钎料钎焊接头组织与性能的影响.在表面工程领域,论述了高熵合金薄膜/涂层的应用方向与制备手段,总结了在高温防护涂层、硬质保护层以及其他应用领域的研究进展.同时归纳了高熵合金在钎焊和表面工程领域研究和应用中存在的问题,而未来将在降低钎料熔点、提高焊缝高温力学性能以及发展共晶高熵合金钎料/涂层等领域进一步提高研究水平.     

ZrB_2-SiC超高温陶瓷非晶钎焊界面组织与力学性能研究

采用Cu_(39.37)Ti_(32.19)Zr_(19.38)Ni_(9.06)(原子比)非晶态钎料对ZrB_2-SiC超高温陶瓷进行钎焊。通过X射线衍射、扫描电镜、万能试验机对钎料的微观结构以及钎焊接头形貌、析出相和室温力学性能进行系统分析。结果表明:在一定钎焊温度下,随钎焊时间的增加,接头剪切强度逐渐减小,且伴随裂纹的出现。在钎焊温度1183 K,钎焊时间30 min时获得的剪切强度最高,约为160 MPa。润湿性实验表明该非晶钎料在ZrB_2-SiC陶瓷表面的润湿性良好。接头剪切强度与钎料和母材之间的反应层厚度有关,通过计算得出反应层厚度形成的激活能Q和反应层生长速度A_0,建立了反应层生长规律的表达式。     

箔状非晶态镍基含磷钎焊料的研究

与同类粉状或膏状钎料相比,非晶态箔状镍基含磷高温钎焊料是100%密度金属钎焊料,具有优良的焊接冶金性能及钎焊工艺性能,与大多数铁基合金有满意的相容性及足够的钎焊接头抗剪切强度,是核工业堆内组件及薄壁耐热蜂窝组件的理想钎焊料。     

定向超合金钎焊接头的冶金研究

本文主要对定向超合金ＤＺ２２采用非晶态镍基、钴基钎料进行了钎焊工艺研究，探讨了钎焊工艺对钎焊接头的组织结构和性能的影响，通过本题研究，取得了接头持久强度达到基体的８０％的结果，这是我所钎焊史上的一个重要突破。     

箔状非晶态镍基含磷纤焊料的研究

与同类粉状或膏状钎料相比，非晶态箔状镍基含磷高温钎焊料是１００％密度金属钎焊料，具有优良的焊接冶金性能及钎焊工艺性能，与大多数铁基合金有满意的相容性及足够的钎焊接头抗剪切强度，是核工业堆内组件及薄壁热蜂窝组件的理想钎焊料。     

TLGA22无银中温钎料及其应用

研制的TLGA22钎料是一种不含银及不含镉等有毒元素的Cu-P-Si系新型钎料。钎料熔化温度为708～720℃,具有优良的钎焊工艺性能和对紫铜钎焊优良的自钎能力。而且,钎缝具有能承受强力旋压变形的特点。钎料抗拉强度达689N/mm~2,搭接接头剪切强度为215.4N/mm~2。它可代替银钎料用于钎焊铜及铜合金。本文还通过与磷含量相同的二元Cu-P合金性能的对比,探讨了该钎料中硅对钎料各方面性能的有益作用,并对其机理进行了分析。     

电子封装无铅软钎焊技术研究进展

软钎焊技术被广泛应用于电子封装领域,可实现电子封装器件与材料之间的互连。SnPb钎料因其良好的润湿性能、焊接性能和合适的价格,一直是电子封装领域中使用较为普遍的钎焊材料。但是,Pb是一种会对人体和环境造成伤害的元素。随着人们环保意识的增强,铅的使用受到了极大的限制,无铅钎料取代SnPb钎料是钎料发展的必然趋势,加速了软钎焊技术向无铅化发展的进程。在钎焊时,助焊剂的性能决定了焊接的效率和质量,因此选择合适的助焊剂是关键。目前,国内外研究学者对无铅软钎焊进行了大量研究,并取得了丰富的成果,例如:通过合金化、颗粒强化等方法研发出多种新型无铅钎料;美、日、欧三方分别发布了无铅钎料和无铅软钎焊发展指南;研发出多种无铅免清洗型助焊剂。因此,基于软钎焊技术的基础研究和应用开发体系已经成熟。应用较为广泛的软钎焊技术有三种,包括波峰焊、回流焊和半导体激光焊。波峰焊一般应用于混合组装方面,回流焊主要应用于表面贴装方面。作为群焊工艺的半导体激光焊经常应用于印刷电路板上焊接电子元件、片状元件的组装等方面。随着电子产品逐渐向小型化和多功能化的方向发展,对连接可靠性的要求越来越高,但基于无铅软钎焊技术的研究和应用开发仍显不足。本文针对电子封装无铅软钎焊技术,探讨了软钎焊技术的研究进展和发展方向。首先,对无铅钎料、助焊剂的种类和组成进行介绍。然后针对无铅化带来的Sn和Cu界面反应的问题,通过Cu基板提出了基板合金化、对基板进行退火处理和化学镀三种解决措施。最后重点阐述了回流焊、波峰焊和半导体激光焊及其应用,为研究电子封装无铅软钎焊技术提供了进一步的理论基础。     

银基钎料在制造业中的研究进展

钎料的性能很大程度上决定了钎焊接头的质量和钎料的应用范畴.银基钎料作为一类非常重要的硬钎焊材料,其填缝能力优异,强度与黄铜、低碳钢接近,可钎焊除铝、镁合金等轻金属之外的所有金属材料.因此,银基钎料广泛应用于航空航天、超硬工具等制造领域,并且受到国内外钎焊界学者们的高度关注.然而,银基钎料的发展及应用过程中仍存在以下问题:第一,钎料中贵金属银含量偏高(一般高于45%),导致钎料使用成本高;第二,银基钎料挤压、轧制、拉拔等加工过程中不可避免地存在夹杂物,影响钎料的使用性能和连接质量;第三,有益金属或合金调控钎料及其连接性能的机制较为复杂,尚未完全研究清楚;第四,传统制备银基钎料的方法产能低下;第五,银基钎料在制造业领域的应用研究尚未见系统报道.国内外对于银基钎料钎焊性能及工程应用方面的研究主要集中于:(1)开发多种节银降银钎料,主要是有益元素调控银基钎料连接性能方面的研究;(2)改进钎料的传统加工方法,提出新的制造方法,如粉末电磁压制成形、钎焊过程中原位合成、快速凝固、镀覆扩散组合等;(3)研究杂质元素(C、Ca、S、Al、Fe、Bi、Pb、O、N 等)的影响;(4)银基钎料形态创新研究,如三明治复合钎料(中间为铜合金、两边为银钎料)、箔带钎料、镀锡银钎料等;(5)工程应用研究,银基钎料在航空航天、汽车制造、电力能源等工业领域起着不可替代的作用,但目前国内外仍缺乏系统阐述该方面研究的报道.因此,本文对近20年国内外有关银基钎料的研究报道进行了评述,重点讨论了合金元素对银基钎料性能的影响.首先对银基钎料研究现状进行详述,总结了Cu、Zn、Sn、Ga、In、Ni、Mn、Cd、Li、Ce、La、P、Si、Pr在银基钎料中的优缺点,归纳了杂质元素C、S、O、N、Ca、Al、Fe、Pb、Bi的恶化作用.其次对银基钎料在航空航天、汽车制造、电力能源、超硬工具、家用电器、眼镜行业等制造业中的应用研究进行详细介绍.最后提出银基钎料研究和应用中的不足,为银基钎料的深入系统研究及相关技术发展提供理论指导.     

碳纤维复合材料与金属连接及接头力学性能测试

碳纤维复合材料因其强度高、质量轻、导热性能出众,在外空间和核工业等领域中的关键部件中得以应用.碳纤维复合材料与金属主要是通过螺栓、胶结、钎焊或扩散焊连接在一起.其中,在钎焊过程中,多数钎料在这类复合材料表面并不润湿,通常采用活性钎料,在高温和高真空的条件下进行;钎料的种类不同,钎焊接头的强度差异也很大.本文对碳纤维复合材料与金属铜、钛、铌、铝等金属的连接方法和相关研究进展作了总结,对其接头的力学性能测试方法作了介绍,并对该领域的研究方向发展做了展望.     

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.……     

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.     

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...     

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 ...