SiC陶瓷真空钎焊接头显微组织和性能

在高真空条件下采用Ti-35Zr-35Ni-15Cu(质量分数/%)钎料对SiC陶瓷进行了钎焊连接,研究了接头界面组织的形成过程以及工艺参数对接头性能的影响。结果表明:钎料与SiC陶瓷发生了复杂的界面反应,生成了多种界面产物。当钎焊温度为960℃,保温时间为10min时,SiC陶瓷侧形成了连续的TiC和Ti5Si3+Zr2Si层,同时Ti5Si3+Zr2Si向钎缝中心生长呈长条状。SiC陶瓷到接头钎缝中心的显微组织依次为:SiC/TiC/Ti5Si3+Zr2Si/Zr(s,s)/Ti(s,s)+Ti2(Cu,Ni)/(Ti,Zr)(Ni,Cu)。钎焊温度为960℃,保温时间为30min时,长条状的Ti5Si3+Zr2Si贯穿了整个接头。钎焊接头强度随着钎焊温度的升高和钎焊时间的延长都呈现先增大后减小的趋势。当钎焊温度为960℃,保温时间为10min时,接头的剪切强度最高,达到了110MPa。     

SiC陶瓷与316L不锈钢真空活性钎焊北大核心CSCD

采用Ag-Cu-Ti活性钎料,通过真空钎焊方法进行了SiC陶瓷与316L不锈钢的连接,研究了接头的界面组织、特征点成分和物相,并探讨了钎焊温度(800～930℃)、保温时间(0～30 min)对接头界面组织和连接强度的影响。结果表明,SiC陶瓷与316L不锈钢钎焊抗剪断口均发生在SiC陶瓷与钎料连接界面处,由于活性元素Ti的作用,在陶瓷与钎料的界面处形成了连续的反应层,反应生成了Ti C和Ti5Si3;在316L不锈钢与钎料的界面处,生成了Fe-Ti化合物和Cu-Ti化合物。随着钎焊温度升高及保温时间延长,接头强度均呈现出一个峰值,在温度为900℃,保温20 min的工艺条件下可获得最大接头抗剪强度。     

采用Ag-Cu-Ti钎料真空钎焊SiO2f/SiO2复合陶瓷与C/C复合材料

分别在880℃/10min和880℃/60min规范下,采用Ag-Cu-Ti活性钎料实现了SiO2f/SiO2复合陶瓷与C/C复合材料的真空钎焊连接,通过电子探针(EPMA)、能谱仪(XEDS)和X射线衍射仪(XRD)分析了接头微观组织,室温下测试了接头的抗剪强度。结果表明:两种规范下所得接头界面结合良好,接头中靠近两侧母材均形成了一层扩散反应层,钎缝基体主要由均匀的共晶组织组成。880℃/10min规范下钎焊接头界面产物依次为:SiO2f/SiO2→Ti4O7→Ti5Si4+Cu(s,s)+Ag-Cu共晶合金→TiC→C/C;对于880℃/60min规范下的接头,界面组织结构与保温10min的接头基本类似,但是不存在Cu(s,s),并且接头反应层明显增厚。880℃/60min条件下所得钎焊接头剪切强度平均值为16.6MPa。     

采用Ag-Cu-In-Ti焊料连接碳化硅陶瓷

采用四元Ag-Cu-In-Ti焊料成功地连接了常压烧结SiC陶瓷. 研究了钎焊温度和保温时间对碳化硅连接强度的影响, 同时通过EPMA和TEM分析连接界面的微观结构, 并且探讨了连接的原理. 试验结果表明, 在700～780℃试验温度范围内, 碳化硅的连接强度存在峰值, 最高四点弯曲强度达到了234MPa, 但是连接强度随着保温时间的增加呈现单调下降趋势. 接头微观结构由基体SiC、反应层和焊料三部分组成, 连续致密的反应层紧密连接基体和焊料, 反应层由带状层、TiC层和Ti5Si3层组成, 带状层宽度约20nm, 由Ag、In、Si和少量的Ti、Cu组成. 元素线扫描结果显示焊料中的活性元素Ti含量在反应层内形成峰值, 活性元素Ti与SiC发生反应生成新的反应层是连接的主要因素.     

采用聚硅氧烷(HPSO VPSO)和Al-Si粉连接无压烧结SiC陶瓷

采用含氢聚硅氧烷(HPSO)和含乙烯基聚硅氧烷(VPSO)2种陶瓷先驱体作为连接剂的主要组分, 以Al-Si粉为填料, 通过反应成形连接工艺连接无压烧结碳化硅。采用热重法、 差示扫描量热法和X射线衍射法研究了Al-Si粉对HPSO和VPSO的混合物(HPSO-VPSO)的裂解过程和陶瓷产率的影响, 同时也研究了Al-Si粉含量、 升温速率及连接温度对连接强度的影响。并采用扫描电镜和能谱仪对连接件界面区域的微观结构和成分进行了分析。Al-Si粉的加入促进了HPSO-VPSO的裂解, 提高了陶瓷产率。当HPSO-VPSO与Al-Si粉质量比为1∶1, 连接压力为50kPa, 连接温度为900℃, 高温保温时间为30min, 升温速率为4℃/min时, 所得连接件的连接强度(剪切强度)达到最大值93MPa。连接层厚度约为75μm, 结构均匀致密, 连接层与母材结合良好, 在界面处没有明显的裂纹、 孔洞等缺陷。Al、 Si元素在连接层与无压烧结碳化硅的界面处发生了扩散, 促进了界面结合, 从而提高了连接强度。      

SiC陶瓷真空钎焊接头的组织及性能分析

采用BNi-5钎料对SiC陶瓷进行真空钎焊,获得了力学性能良好的SiC钎焊接头,并对焊缝的微观结构和形成过程进行了分析。研究结果表明,Ni基钎料与SiC母材发生反应生成层状界面反应层结构,所形成的SiC钎焊接头钎缝微观形貌可以表述为:SiC母材/石墨+Ni_2Si/Ni_2Si/石墨+Ni_2Si/Cr_3Ni_2SiC/Ni+Cr_3Ni_5Si_2/Cr_3Ni_2SiC/石墨+Ni_2Si/Ni_2Si/石墨+Ni_2Si/SiC母材。所得SiC钎焊接头常温力学性能较好,平均钎焊接头剪切强度可达到124 MPa。Ni基钎料钎焊SiC陶瓷接头的断裂位置位于钎料与陶瓷基体间的界面反应层,主要原因是界面反应层中Ni_2Si和Cr_3Ni_2SiC等脆性化合物在钎焊接头拉伸变形过程中会产生应力集中,在残余钎焊应力的共同作用下钎焊接头发生断裂。     

电流辅助下CoFeCrNiCuTi2高熵合金钎焊SiC陶瓷接头组织与性能

采用电流辅助连接技术，以CoFeCrNiCuTi₂高熵合金为连接层材料，在1125℃的温度下，实现了SiC陶瓷的快速钎焊，提高了连接效率的同时保证了元素的充分扩散，系统研究了钎焊温度对连接接头界面微观结构和力学性能的影响。结果表明：所获得的钎焊接头无明显缺陷，焊缝组织主要由高熵FCC相、TiC相、Cr₂₃C₆相组成。界面致密的TiC反应层的形成在一定程度上抑制了高熵合金的分解和金属间化合物的生成，并缓解了SiC基体界面与高熵合金钎料之间的热应力。同时，由于高熵合金钎料的迟滞扩散效应，焊缝中心主体钎料仍保持高熵合金的FCC结构。力学性能测试表明：钎焊接头强度随钎焊温度升高呈先降低后增大的变化趋势。当连接温度为1125℃时，碳化硅接头获得最大弯曲强度，达到37 MPa,高于普通镍基钎料约21.3 MPa。     

SiC陶瓷与316L不锈钢真空活性钎焊

采用Ag-Cu-Ti活性钎料,通过真空钎焊方法进行了SiC陶瓷与316L不锈钢的连接,研究了接头的界面组织、特征点成分和物相,并探讨了钎焊温度(800～930℃)、保温时间(0～30 min)对接头界面组织和连接强度的影响。结果表明,SiC陶瓷与316L不锈钢钎焊抗剪断口均发生在SiC陶瓷与钎料连接界面处,由于活性元素Ti的作用,在陶瓷与钎料的界面处形成了连续的反应层,反应生成了Ti C和Ti5Si3;在316L不锈钢与钎料的界面处,生成了Fe-Ti化合物和Cu-Ti化合物。随着钎焊温度升高及保温时间延长,接头强度均呈现出一个峰值,在温度为900℃,保温20 min的工艺条件下可获得最大接头抗剪强度。     

活性钎焊法连接碳化硅陶瓷的连接强度和微观结构

采用三元Ag-Cu-Ti活性焊料连接常压烧结碳化硅陶瓷,研究了反应温度、保温时间等钎焊工艺对碳化硅陶瓷连接强度的影响,分析了连接界面的微观结构和反应产物. 实验结果表明,在实验范围内,钎焊温度和保温时间对碳化硅陶瓷的连接强度均有峰值,四点弯曲强度最高达到342MPa,随着钎焊温度的升高,界面反应层厚度增加,连接强度提高,但过高的钎焊温度引起焊料的挥发而使连接强度下降. 焊料中的活性元素Ti与碳化硅发生反应在连接界面形成均匀致密的反应层,反应层厚度约1μm,XRD和EDX能谱分析结果表明反应产物是TiC和Ti₅Si₃.     

采用Ag-Cu-Ti钎料钎焊Cf/SiC接头的组织和强度

选用Ag-35.5Cu-1.8Ti和Ag-27.4Cu-4.4Ti两种钎料,在880℃/10min钎焊规范下进行了Cf/SiC陶瓷基复合材料的钎焊实验。实验结果表明,钎焊接头中央为典型的Ag-Cu共晶组织,而在钎料与Cf/SiC母材的界面处形成了扩散反应层,Ti在该层中富集。通过界面X射线衍射分析,确定界面存在TiC相,但未检测到Ti-Si相。分析了界面反应机理。接头强度试验结果表明,采用Ag-35.5Cu-1.8Ti钎料获得接头的三点弯曲强度为132.5MPa,而Ag-27.4Cu-4.4Ti对应的接头强度为159.5MPa,分析认为,Ti在钎料中的活性是决定接头性能的关键因素之一,即接头强度随着钎料中Ti活性的提高而呈现增加的趋势。     

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.     

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.     

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.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to