Cu-Zn-Al 形状记忆合金马氏体相变热力学

对不同成分的 Cu-Zn-Al 合金中无序α与β相的平衡温度 T_0~*,有序α′与β′相的平衡温度 T_0(母相为 L2_1有序结构)及各种有序母相所得 M_s 进行了系统的计算。用电阻法测试了直接淬火及分级淬火试样的相变温度。结果表明,当母相为 L2_1有序结构时,理论计算的 M_s 值与分级淬火试样 M_s 的实验值吻合。计算还证明,相对无序结构母相 B2或 DO_3有序化均引起 M_s 下降,前者使 M_s 下降更多。     

Cu-Zn 合金马氏体相变热力学

假定 Cu-Zn 合金马氏体相变中新、旧原子存在 Bain 机制所示的对应关系,则沿用已知的热力学数据,以 BWG 模型处理 Cu-Zn 合金的有序问题,推导出相变驱动力ΔG~(β′→α′)的普遍表达式。以该式计算了Cu-Zn 合金马氏体相变的平衡温度 T(?)及马氏体相变点 M_s,其中 M_s 与实验结果很好吻合。计算证明,母相有序化是 Cu-Zn 合金发生热弹性马氏体相变的必要条件,有序度对 M_s 有显著的影响。     

Cu-Zn 合金贝氏体相变热力学

对 Cu-40at.-%Zn 合金贝氏体相变温度范围内各种可能相变的驱动力进行了计算。结果表明,由于在这温度范围内存在β→β′有序相变,因而相变驱动力ΔG~(β′→α′)及ΔG~(β′→β_1′+α)随温度下降反而增大,且ΔG~(β′→α′)>0,ΔG~(β′→β_1′+α)<0;而且各成分合金β′及α′两相平衡温度 T_0,远低于 B_s 实验值,所以贝氏体相变只能按β′→β_1′+α扩散型相变进行。     

金相法测定锆锡和锆铌系锆合金的相变温度

采用金相法测定了锆锡系Zr4锆合金和锆铌系N36锆合金由α+β相转变为β相的相变温度T_(α+β→β)。结果表明:可以通过金相法测定锆合金的相变温度T_(α+β→β),在相变温度T_(α+β→β)附近淬火,通过观察试样α相含量的变化,确定α相未完全转变和完全转变的温度区间,相变温度T_(α+β→β)取该区间的下限值,热处理加热温度间隔建议选择为10℃;试验测得Zr4锆合金的T_(α+β→β)为970℃,N36锆合金的T_(α+β→β)为890℃。     

用中心原子模型计算 Fe-C合金马氏体相变驱动力和相变点

根据已发表的活度数据,重新讨论了 Fe-C 合金中心原子模型(CAM)中的热力学参数。利用中心原子模型计算了 Fe-C 合金的马氏体相变驱动力和 M_s。计算结果表明,碳含量较低时,Fe-C 合金马氏体相变驱动力与碳含量成线性递增关系。根据计算结果和徐模型推算了 Fe-C 合金奥氏体在 M_s点的强度。M_s 的计算与实验结果符合得较好。由 CAM 模型得到:M_s(K)=834-8277x_c     

CALCULATION OF THE DRIVING FORCE AND Ms FOR MARTENSITIC TRANSFORMATION IN Fe-C ALLOYS FROM THE CENTRAL ATOMS MODEL

根据已发表的活度数据,重新讨论了Fe-C 合金中心原子模型(CAM)中的热力学参数。利用中心原子模型计算了Fe-C 合金的马氏体相变驱动力和M_s。计算结果表明,碳含量较低时,Fe-C 合金马氏体相变驱动力与碳含量成线性递增关系。根据计算结果和徐模型推算了Fe-C 合金奥氏体在M_s点的强度。M_s 的计算与实验结果符合得较好。由CAM 模型得到:M_s(K)=834-8277x_c     

铁基合金马氏体相变热力学

铁基合金中 fcc→bcc(bct)马氏体相变时的自由能改变可由△G~(γ→M)=△G~(γ→(?)+△G~(γ→M)(非化学自由能)表示。M_s定义为△G~(γ→M)=0的温度。在 Ms 时,-△G~(γ→α)=△G~((?)→M),即为临界相变动力。对计算△G~(γ→α)的几个改进模型作了评述。对△G~(α→M)项作出合理的估计,由△G~(γ→(?))和△G~(α→M)即可直接计算求得 M_s,这在纯铁、Fe-C、一些 Fe-X、Fe-X-C 合金及多元低合金钢(包括渗层)中获得满意的结果。合金元素和碳对 M_s 的影响得到热力学的阐释。相变驱动力的计算值不仅依赖于△G~(γ→α)的计算模型,而且还极大地取决于△G~(γ→α)_(Fe)及 M_s 值的选用。计算表明,Fe—C 中,随含碳量增加,相变驱动力将单调地增大。     

NiTiCu合金相变过程的研究

本文用差示扫描量热法研究了 Cu 对 NiTi 记忆合金马氏体相变点及相变潜热的影响。结果表明,以 Cu 代替 Ni 至30 at.%,合金仍具有良好的记忆性能;合金相变温度及相变潜热值略有变化,相变滞后明显减小;Cu 含量对合金相变类型没有影响。相变潜热值△H 与 T_0=1/2(A_s+M_s)并不存在严格的直线关系。Cu 含量超过7.5at.—%时,合金的热加工性能变差。     

Ti-4．4A1—3．8Mo合金的亚稳相变及其对硬度的影响

对锻态Ti-4．4Al-3．8Mo合金分别进行了β单相区和α＋β两相区（相变点之下45℃）淬火处理,研究了亚稳相变对硬度的影响．结果表明,β单相区淬火处理的样品硬度比α＋β两相区处理的样品高约10％．β单相区淬火后的相组成为全α’马氏体,自910℃的α＋β两相区淬火后的相组成为等轴初生α相＋α’马氏体＋α″马氏体．硬度出现差异的主要原因是后者中存在硬度较低的初生α相和α″马氏体．本文修正了Ti—β稳定元素二元系亚稳相图（示意图）,指出在α＋α’和α＋α″相区之间存在α＋α’＋α″相区,并使用修正后的相图解释了Ti-4．4Al-3．8Mo合金的相组成与硬度的关系．     

淬火温度对Ti-3Al-4.5V-5Mo钛合金形变诱发马氏体的影响

通过测试不同淬火温度下的拉伸应力应变曲线、750～790℃淬火拉伸断裂后均匀变形区域的X射线衍射谱研究了淬火温度对Ti-3Al-4.5V-5Mo钛合金形变诱发马氏体的影响.结果表明:该合金在750～790℃淬火后拉伸变形机制为亚稳定β相变形诱发马氏体转变,790℃淬火合金在6.5%的变形量下亚稳定β相基本完全转变为α″马氏体.790℃淬火后拉伸形成应力诱发马氏体,β立方→α″σ;750℃淬火后拉伸形成应变诱发马氏体,β立方→β正方→α″ε.形变诱发α″相在拉伸变形时发生晶格重新取向:[010] α″方向平行于拉伸轴线,[100]α″方向垂直于拉伸轴线.     

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.……     

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.     

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 ...