凝固速率对DZ22合金力学性能和组织的影响EI

本文采用ＺＭＬＭＣ超高梯度定向凝固法（ＺＭＬＭＣ法），研究了两种凝固速率下ＤＺ２２合金的高温力学性能和组织。结果表明，较高凝固速率下大幅度地提高了合金的高温力学性能，９８０℃，２２０ＭＰａ条件下的高温持久寿命由７１ｈ５０ｍｉｎ提高到１６８ｈ５ｍｉｎ；一次、二次枝晶臂间距λ＿１和λ＿２分别由１０５μｍ和３２．７μｍ左右减小到６８μｍ和１６μｍ左右；元素的枝晶偏析得到抑制；合金显微组织的组成相γ＇、（γ－γ＇）共晶、ＭＣ型碳化物的形态、大小和分布均发生了明显的变化。     

单晶高温合金DD3亚结构超细化定向凝固工艺研究EI

利用ＺＭ定向凝固装置研究了镍基单晶高温合金ＤＤ３在高温度梯度（７００～１２００Ｋ／ｃｍ）定向凝固条件下的微观组织演化特征及其对工艺参数的响应函数，结果表明：该合金在高界面温度梯度条件下，柱晶生长速度范围向高速区扩展，从而使单晶亚结构细化成为可能。所得单晶棒中亚结构一次间距可比传统ＨＲＳ法定向凝固籽晶中相应尺度减小５～１０倍。本文还对其组织演化机制进行了分析。     

自生复合Cu08Cr合金定向凝固过程研究

研究了非平衡状态下Ｃｕ０８ｗｔ％ Ｃｒ 亚共晶合金的定向凝固过程。结果表明, 当温度梯度为３０℃／ｃｍ , 生长速度分别为３μｍ ／ｓ 和３０μｍ ／ｓ 时, Ｃｕ０８ｗ ｔ％ Ｃｒ 合金呈（α枝晶＋ 共晶） 的非平衡凝固组织; 当温度梯度为３０℃／ｃｍ 时, α枝晶一次间距随生长速度的增大而增大, 这与枝晶一次间距的Ｈｕｎｔ模型在低速度段的规律一致, 而与ＫＰ模型的规律相反; Ｃｒ 纤维的形成主要与液态Ｃｒ 的表面张力、Ｃｒ 原子在液相中横向扩散能力及α枝晶间Ｃｒ 相的生长环境有关,增强Ｃｒ 原子的扩散能力,减小α枝晶侧向分枝及其间隙尺寸有助于规则Ｃｒ纤维的形成。     

镍基高温合金超细定向柱晶的凝固特性

本文采用超高梯度快速定向凝固装置研究了镍基铸造高温合金 K405超细定向柱晶的凝固特性。试验结果表明,当温度梯度为660K/cm 和凝固速率为760μm/s时,可获得超细柱晶体,其一次、二次枝晶间距λ_1和λ_2分别小于25μm 和10μm;Cr,Al,Ti,W,Co 等元素的偏析比均趋近于1;γ′相分布均匀,(γ+γ′)共晶基本消除,MC 碳化物呈点状和小条状沿一次枝晶轴方向均匀分布于枝晶间。     

K5合金高梯度下快速凝固定向组织的研究

本文利用自行研制的超高梯度定向凝固装置（ＺＭＬＭＣ），考察镍基高温合金Ｋ５在不同的凝固速率下特别是在高速下定向组织的生长行为。研究表明，利用该定向凝固装置可获得完全细化的定向超细晶组织。     

两种定向凝固方法DZ22合金的力学性能和组织

比较了超高梯度定向凝固法（ＺＭＬＭＣ法）和普通定向凝固法（ＨＲＳ法）对ＤＺ２２合金的高温力学性能和组织的影响。结果表明：ＺＭＬＭＣ法大幅度地提高了合金的高温力学性能，９８０℃，２２０ＭＰａ条件下的高温持久寿命由７２ｈ提高到１６８ｈ；一次、二次枝晶臂间距λ１和λ２分别由１５０ｕｍ和５０ｕｍ左右到减小到６８ｕｍ和１６ｕｍ左右；元素的枝晶偏析得到抑制；合金显微组织的组成相ｒ’，（ｒ＋ｒ’）共晶，ＭＣ型碳     

一次枝晶间距模型及在单晶高温合金中的验证

本文评述了二元系统一次枝晶间距模型的发展及特点，并验证了在多元合金系统中的适用性，结果表明，在ＤＤ８单晶高温合金中，λ１－Ｇ关系符合二元系统模型，但λ１－Ｖ关系和二元系统模型有较大的偏离，λ１为一次枝晶间距，Ｇ为温度梯度，Ｖ为凝固速率，在本文凝固条件下，ＤＤ８合金的λ１－Ｇ，Ｖ关系式为：λ１＝１１４１．５Ｇ＾－０．５２Ｖ＾－０．１２，其中λ１单位为μｍ，Ｇ为Ｋ／ｍｍ，Ｖ为μｍ／ｓ。     

温度梯度对定向凝固Al-4.5%Cu合金一次枝晶间距的影响

使用5kg坩埚下拉式定向凝固设备,对Al-4.5%Cu合金进行定向凝固试验,研究Al-4.5%Cu合金在不同温度梯度下一次枝晶间距的变化规律。结果表明:在其他凝固参数不变时,随着温度梯度的增大,一次枝晶逐渐变小,细密,挺直,基本呈平行状分布,同时计算的一次枝晶间距值与Hunt模型计算值接近,实验测得的一次枝晶间距的回归曲线为:y=2843478.3x2-70217.4x+543.8。用温度梯度较高的实验值来模拟时,可得到1λ=26.7G-0.5-135.9,一次枝晶间距λ1与G-0.5基本呈线性关系,这和Hunt模型分析结果一致。     

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。     

自生复合Cu-0.8Cr合金定向凝固过程研究

研究了非平衡状态下Ｃｒ－０．８ｗｔ％Ｃｒ亚共晶合金的定向凝固过程。结果表明,当温度梯度为３０℃／ｃｍ,生长速度分别为３μｍ／ｓ和３０μｍ／ｓ时,Ｃｕ－０．８ｗｔ％Ｃｒ合金的非平衡凝固组织;当温度梯度为３０℃／ｃｍ时,α枝晶一次间距随生长速度的增大而增大,这与枝晶一次间跨的Ｈｕｎｔ模型在低束祺段的规律一致,而与Ｋ－Ｐ模型的规律相反;Ｃｒ纤维的形成主要与液态Ｃｒ表面张力,Ｃｒ原子在液相中横向扩散能力及     

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.     

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 ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.