钛合金双片层组织对性能的影响

研究了通过热处理制度调整,在合金α片层之间形成细小的条状次生α相,形成一种新型的钛合金显微组织——双片层组织.通过对比等轴组织、双态组织、片层组织和双片层组织的性能,结果表明,在合金的强度和塑性不损失的条件下,双片层组织进一步提高了裂纹在合金中的扩展阻抗,使得合金的断裂韧性得到改善,疲劳裂纹扩展速率得到降低.双片层组织...     

显微组织及频率对Ti_3Al基合金疲劳裂纹扩展速率的影响EI北大核心

以不同的频率对具有不同显微组织的Ti3Al基合金的疲劳裂纹扩展行为进行了研究。结果表明,显微组织及频率对材料的da/dN有强烈的影响,1080℃固溶处理组织具有最低的疲劳裂纹扩展速率,1110℃固溶处理组织具有最高的疲劳裂纹扩展速率。随着频率的降低,三种显微组织的疲劳裂纹扩展速率都有所增加。初生α2相的体积分数是影响疲劳扩展速率的重要因素。含有初生α2相的组织及不含初生α2相的组织的疲劳裂纹扩展有不同的机制。     

激光熔覆修复对TC4钛合金疲劳裂纹扩展速率的影响

为了研究激光熔覆修复对TC4钛合金疲劳裂纹扩展速率的影响,采用激光熔覆技术,通过逐层堆积TC4钛粉,对TC4钛合金板表面凹槽进行修复。利用光学显微镜和扫描电镜分别观测试样的微观结构和疲劳断口,采用疲劳裂纹扩展实验测定试样裂纹长度与循环次数,利用修正的七点递增多项式拟合法获得每组3个试样在相同裂纹长度下的疲劳裂纹扩展速率。实验结果表明:激光修复区由β晶粒和沿晶界连续分布的α相组成,属于典型的魏氏组织,热影响区由等轴的α晶粒和β转变组织组成,属于典型的双态组织;同母材相比,激光熔覆修复件疲劳裂纹扩展速率显著降低。TC4钛合金熔覆修复件抗疲劳裂纹扩展能力的提高归因于魏氏组织断裂韧性高和双态组织优异的综合力学性能。     

两种组织TC11钛合金薄板弯曲疲劳性能的研究

本研究选取了具有（α＋β）等轴组织和α／β粗片层组织的TCll钛合金作为研究对象,采用研究了TCll合金薄板样品在恒总应变幅控制下的弯曲疲劳性能及其损伤行为,通过对疲劳开裂路径和断裂的观察与表征,探讨了疲劳损伤与组织结构间的关系。研究发现,恒总应变幅控制下的等轴组织TCll钛合金薄板的弯曲疲劳性能明显的高于粗片层组织合金。等轴组织合金的疲劳裂纹沿α相中的滑移带萌生并扩展,片层组织样品疲劳裂纹沿着α相或与片层垂直的方向扩展。     

船用铸造高强度铜合金腐蚀疲劳性能的研究

本文模拟船用螺旋桨的受力状态及工作环境,采用小试样,低应力高周疲劳试验进行裂纹扩展观察,来研究螺旋浆铜合金材料的腐蚀疲劳性能。重点测定裂纹扩展速率dα/dN,并通过dα/dN来估算疲劳裂纹扩展寿命,评定五种铜合金的优劣。同时对比研究了这几种钢合金的化学成分,铸态组织,常规力学性能及腐蚀疲劳性能的内在联系。指出在本实验中满足δ_5≥20％时,随着强度的增高,合金的抗腐蚀疲劳性能提高。提高合金的强度仍是提高螺旋桨使用寿命的主要方法。对同一牌号的黄铜,锌当量的不同对腐蚀疲劳性能有显著的影响,适当控制锌当量即合金组织中α相与β相的比例,也是提高螺旋桨使用寿命的一个途径。     

Tc11钛合金盘的显微组织断裂形态及断裂韧性间的关系

经常规锻造、近β锻造和β锻造的Tell(Ti—6.5Al—3.5Mo—1.5Zr—0.3Si)钛合金盘获不同的显微组织,对应了不同的断裂韧性。在常规锻造的等轴组织中,虽然可以观察到穿过等轴α相的二次裂纹,但裂纹扩展路径平直,分枝少,断裂表面光滑平整,因而断裂韧性低。近β锻造得到双态组织,由于等轴α相含量的减少,魏氏α相比例增多和形态的改变,二次裂纹增加,断裂韧性显著提高。在β锻造的网篮组织中,α条上的疲劳条带和二次裂纹明显增加,裂纹扩展路径曲折,分枝多,故断裂韧性最高。可见,显微组织影响盘件断裂韧性的主要因素在于,裂纹扩展过程中产生的裂纹分枝、疲劳条纹和二次裂纹的密度以及裂纹扩展路径的曲折程度。     

固溶处理对TC11钛合金棒材组织和性能的影响

通过场发射扫描电镜及拉伸性能测试,研究了TC11钛合金棒材3种固溶处理时间和2种固溶方式对显微组织及力学性能的影响。结果表明:TC11钛合金在经过3 h的固溶后,组织中局部的亚稳定β晶体位相发生偏转,β转变组织中的次生α相变的粗大,经过后续时效后的β转变基体发生更为充分的分解和析出,在片层的β边界出现连续的更细小的次生α相。由于固溶时间延长,发生了过固溶,析出的次生相逐渐细小,导致裂纹扩展阻力降低,引起屈服强度的降低,分开各1 h的固溶时效性能低于连续2 h的固溶时效性能。     

TC4-DT钛合金疲劳裂纹扩展的微观机制

通过断口分析讨论了TC4-DT钛合金裂纹扩展的微观机制。从微裂纹的形成,疲劳裂纹初期、近门槛区以及稳态区的扩展,分析了不同组织形态的TC4-DT钛合金对应的裂纹扩展微观机制。分析结果表明,对于片层组织,循环载荷的作用导致断裂表面粗糙及塑性变形过程中相界面产生位错塞积而诱使裂纹萌生。等轴组织变形过程中晶粒产生的断裂表面成为裂纹的萌生源。在近门槛区,等轴组织变形过程中位错累积将导致沿晶界的开裂,从而加速裂纹扩展;双片层组织由于次生α相的尺寸效应会加速裂纹扩展。在稳态扩展区,断口表面由第Ⅰ阶段的锯齿状断裂模式过渡到辉纹断裂模式,表现为塑性条带断裂机制。     

显微组织对Ti-6Al-4V ELI合金疲劳裂纹扩展速率的影响

研究了Ti-6Al-4V ELI合金板材的显微组织对疲劳裂纹扩展速率的影响.用金相显微镜对不同热处理制度下该合金α和β转变组织的变化进行了观察分析.采用MTS-810低周疲劳试验机测试合金的裂纹扩展速率.通过Origin 6.0软件对数据进行处理并绘制裂纹扩展速率(△a/△N)与应力强度因子幅△K的关系曲线.结果表明:在Pairs区范围内,疲劳裂纹扩展速率对双态组织中初生α相含量的多少不敏感,而在近门槛区和快速扩展区,裂纹扩展速率对组织比较敏感;在本实验研究的条件下,细针编织状魏氏组织的da/dN<平直状片层组织的da/dN<双态组织的da/dN.     

超塑成形/扩散连接热环境对Ti-6Al-4V合金疲劳性能的影响

采用光学显微镜研究了Ti-6Al-4V合金经超塑成形/扩散连接(SPF/DB)热影响后的微观组织演变,在室温和空气条件下进行了旋转弯曲疲劳试验,并采用扫描电子显微镜对试样断口形貌进行了观察.结果表明:Ti-6Al-4V合金经历SPF/DB热工艺后,初始的双态组织转变为了等轴组织;强度有所降低,塑性略有提高,而旋转弯曲疲劳极限从420 MPa降低至405 MPa,在相同应力条件下(σ=431 MPa),SPF/DB后试样的疲劳寿命从10⁷量级降低至10⁶量级;疲劳断口源区附近的放射线增粗且变的不连贯,疲劳裂纹扩展区的疲劳条带间距增大,裂纹扩展速率提高.这主要是由于SPF/DB热环境使Ti-6Al-4V合金片层α数量显著减少,降低了晶界总体长度,减弱了α相晶界对疲劳小裂纹扩展的阻碍作用.     

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.……     

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...     

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.……     

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.     

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