Zn对Mg-6Al合金凝固的溶质偏析及组织的影响

采用液态淬火方法得到了Mg-6Al和Mg-6Al-0.5Zn合金固液共存界面试样,表征了溶质Al在这两种合金中的凝 固偏析特征,研究了Zn对Mg-6A1合金凝固溶质偏析和凝固组织的影响.结果表明:Al元素在Mg-6A1合金中的近平衡分配系数是0.33,偏析比为2.17,最大偏析率为0.43.Zn的加入使Mg-6A1合金...     

二元固溶体型合金凝固过程中固相分数的变化规律

本文首先总结了前人在固相分数计算方面的研究工作。通过对几个主要影响因素的分析,指出了以前所用计算式的适用范围。进而通过对作者最近提出的局部溶质再分配方程修正式的求解,得出了板状技晶和柱状枝晶两种生长形态下适用范围更广的计算式。最后以Al—4.5％Cu合金枝晶生长过程为例,对各式的计算结果进行了对比讨论。并估算了非平衡共晶和θ相的析出量。     

单晶 Ni 基高温合金侧向约束条件下的凝固行为

研究了侧向约束条件下单晶 Ni 基高温合金的凝固行为及溶质再分配。实验结果表明:侧向约束条件对单晶 Ni 基高温合金的凝固组织、溶质偏析及溶质再分配均具有极为强烈的影响。侧向约束条件即试样断面变化对单晶 Ni 基高温合金凝固过程的影响,实质上是局部凝固工艺参数的影响。本文研究结果对实际单晶 Ni 基高温合金铸件凝固组织的控制和生产具有重要的指导意义。     

等轴晶移动对宏观偏析影响的数值模拟

建立了自由等轴晶移动对宏观偏析影响的数学模型,对铸锭凝固过程中的对流和溶质分布进行了数值模拟.在模型中按照临界固相分数将糊状区分为紧密树枝晶和自由等轴晶两个不同的区域.对带冒口铸钢锭的宏观偏析进行了数值模拟,并同实验结果进行了比较.与假设糊状区内固相静止的模型相比,考虑等轴晶移动的模型得到的溶质分布结果与实验结果更接近.在凝固过程中,等轴晶随液体流动并在铸锭的底部中心聚集,在凝固后的铸锭中形成锥形的负偏析.还发现,在铸锭的中心靠上的区域形成正偏析,在铸锭的外部区域形成负偏析.     

快速凝固的非平衡效应研究

综述了快速凝固对凝固组织尺寸、溶质再分配、相选择与相分离、固液界面结构与生长方式以及材料性能的影响.分析了快速凝固的非平衡效应及形成机制的研究进展,指出了现有理论的局限性.有效利用材料的非平衡效应结果将有利于改进材料的性能.     

Al-Y包晶合金非平衡凝固过程及组织特征

包晶凝固过程中小平面-小平面两相复相生长方式是凝固领域研究的一个热点。以初生相和包晶相都是严格计量比金属间化合物的Al-Y包晶合金作为研究对象,利用DSC热分析技术,严格控制冷却速度,获得不同凝固条件的非平衡凝固试样,研究了两相为小平面相的Al-Y包晶合金的凝固行为。发现小平面-小平面包晶系合金包晶凝固过程中,非平衡凝固特性及宏观偏析特点比非小平面包晶系更加明显。凝固特征温度与平衡相图偏差明显,包晶反应温度和包晶相直接凝固温度都远高于平衡相图给定的值,相对于相图是在"过热"条件下发生的,而固溶体型包晶合金一般是在"过冷"条件下发生的。包晶转变过程非常微弱,致使初生相残留量远高于平衡相图。即使对于过包晶成分的合金,其凝固组织中仍存在大量的共晶凝固组织,最终得到的凝固组织与平衡相图存在显著差异。     

凝固速率对IN718合金定向凝固组织和偏析行为的影响

采用LMC高梯度定向凝固和微观分析方法,研究了不同凝固速率下IN718合金的凝固组织和偏析行为。结果表明,随着凝固速率的提高,凝固界面由胞晶转为枝晶;一次胞/枝晶间距在凝固速率为20μm/s时提高到最大值257μm,随后逐渐降低,二次枝晶间距明显细化,溶质分配比也随凝固速率的增加而减小。同时,凝固速率增加使糊状区枝晶骨架的渗透性减小,增大了对液体流动的阻碍作用。     

一种Ni-Cr-Mo镍基合金焊丝凝固过程元素偏析及相转变规律研究

为了对Ni-Cr-Mo镍基合金焊丝进行成分优化设计,本文通过热力学模拟计算方法研究了镍基合金焊丝凝固过程元素的偏析规律,并分析了合金元素对析出相的影响.研究表明:镍基合金焊丝平衡态主要的析出相为γ、M6C、P和μ相;在非平衡凝固状态下,随着凝固过程的推进从液相中析出M6C、P和σ相;随着Cr含量的增加,μ相的初始析出温...     

Simulation of dendrite growth of Fe–C alloy using phase field method

采用相场法模拟了Fe--0.5%C合金等温凝固过程中单个枝晶和多个枝晶的生长, 研究了过冷度、各向异性、界面厚度、晶体取向以及扰动对枝晶形貌的影响, 获得了具有二次分枝的枝晶形貌, 再现了枝晶生长过程及枝晶臂之间的竞争生长. 模拟结果表明: 凝固过程中存在溶质富集和枝晶偏析, 枝晶主干溶质浓度最低, 枝晶臂之间的液相浓度最高. 随着过冷度的增大, 枝晶生长加快且分枝发达; 界面厚度直接影响枝晶的生长速度; 各向异性影响枝晶的形态; 晶体取向与坐标轴方向一致时枝晶优先生长;扰动的加入导致枝晶分枝的形成.     

用相场方法模拟Fe-C合金枝晶生长

采用相场法模拟了Fe-0.5%C合金等温凝固过程中单个枝晶和多个枝晶的生长,研究了过冷度、各向异性、界面厚度、晶体取向以及扰动对枝晶形貌的影响,获得了具有二次分枝的枝晶形貌,再现了枝晶生长过程及枝晶臂之间的竞争生长.模拟结果表明:凝固过程中存在溶质富集和枝晶偏析,枝晶主干溶质浓度最低,枝晶臂之间的液相浓度最高.随着过冷度的增大,枝晶生长加快且分枝发达;界面厚度直接影响枝晶的生长速度;各向异性影响枝晶的形态;晶体取向与坐标轴方向一致时枝晶优先生长;扰动的加入导致枝晶分枝的形成.     

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