氢对Ti-6Al-4V合金室温压缩性能的影响

为了研究氢对Ti-6Al-4V合金室温压缩性能的影响,采用Zwick/Z100型材料试验机对置氢Ti-6Al-4V合金进行了压缩试验,并利用OM、XRD和TEM等材料分析方法对合金的微观组织进行了观察.研究表明:置氢前,Ti-6Al-4V合金由等轴的α相和β相组成,置氢后,出现马氏体组织和氢化物;随氢含量增加,马氏体和剩余β相数量增多;氢提高了Ti-6Al-4V合金的抗压强度和塑性等室温压缩性能,最大增幅分别为33.9%和56.3%;置氢Ti-6Al-4V合金抗压强度的提高主要归因于氢的固溶强化、马氏体相变强化和氢化物强化;塑性指标的提高主要是置氢合金中塑性β相数量的增多所致.     

固溶冷却速率对全片层亚稳β钛合金α相形貌的影响EI北大核心CSCD

采用Gleeble热模拟压缩试验机、显微硬度计、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等研究固溶冷却速率对TB17钛合金力学性能和条状α形貌的影响。结果表明:具有网篮组织的TB17钛合金经两相区固溶后,当固溶冷却速率为200℃/min时,合金显微硬度为250HV,随着固溶冷却速率的降低,钛合金显微硬度逐渐增加,当固溶冷却速率降低到1℃/min(炉冷)时,显微硬度增加到320HV。在连续冷却过程中会发生β→α相变,在β基体上析出次生α相,同时条状α相会转变为“叉状”结构;随着固溶冷却速率的降低,“叉状”结构逐渐变粗长大,当固溶冷却速率为40℃/min时,“叉状”结构的宽度约为14 nm,当固溶冷却速率为10℃/min时,“叉状”结构的宽度约为100 nm,当固溶冷却速率为1℃/min(炉冷)时,“叉状”结构的宽度约为300 nm;而当固溶冷却速率大于10℃/min时,条状α相侧面和端面包裹着斜方马氏体α″相,马氏体相的存在促进了α相转变和“叉状”结构的形成。当固溶冷却速率逐渐降低至1℃/min左右相当于炉冷速率时,“叉状”结构变粗,条状α相端面和侧面的斜方马氏体相消失,发生α″→α相变。     

一种汽车用微合金非调质钢的连续冷却转变

测定了一种汽车用微合金非调质钢的过冷奥氏体连续冷却转变曲线,研究了冷却速率对相变组织及显微硬度的影响。结果表明：试验钢的临界点A_c3为838℃,A_c1为732℃;当冷却速率小于0.2℃/s时,试验钢的连续冷却转变产物为铁素体、珠光体和贝氏体;当冷却速率为0.2℃/s时,转变产物中出现马氏体;当冷却速率为5℃/s时,铁素体、珠光体消失,转变产物为贝氏体和马氏体;随着冷却速率的增大,马氏体含量逐渐增多,贝氏体含量逐渐减少,甚至完全消失;当冷却速率增大至20℃/s时,转变产物均为马氏体;随着冷却速率的增大,试验钢的显微硬度呈先快速增长,后增长速率变缓的趋势。     

Q690D高强度钢的动态连续冷却转变曲线

在热模拟试验机上对Q690D高强度钢进行不同冷却速率的热模拟试验,绘制动态连续冷却转变曲线,用光学显微镜观察该钢的显微组织,用维氏硬度计测试其维氏硬度。结果表明：当冷却速率小于0.1℃/s时,Q690D高强度钢的组织基本为珠光体、铁素体和少量贝氏体;当冷却速率为0.5℃/s时,珠光体消失,组织全部为贝氏体;当冷却速率为3℃/s时,组织中出现马氏体;当冷却速率增大至8℃/s时,贝氏体几乎全部消失,基体组织基本为马氏体;当冷却速率大于10℃/s时,组织全部为马氏体,得到马氏体临界转变冷却速率为10℃/s。     

激光焊接Ti-6Al-4V钛合金塑性行为的原位SEM/EBSD分析（英文）

选用原位SEM/EBSD显微术分析研究了Ti-6Al-4V钛合金的焊接区域的变形行为。研究发现,由于焊接时高的焊接温度(在β相变点之上)和急剧的冷却速率,导致β→α'马氏体相变的发生。SEM观察发现,在焊缝区只存在有针状的α'马氏体形貌,而在焊接第一热影响区和第二热影响区,针状α'相逐渐发生球化,形成了明显的显微组织梯度过渡。在对焊接区域进行SEM/EBSD下的原位拉伸实验后发现,该区域的塑性变形可划分为两个阶段。变形的第一阶段,滑移变形或孪生变形均有可能发生,这取决于晶粒的初始晶体学取向是否可通过旋转来匹配120//TA(拉伸方向);而在变形的第二阶段,只发生滑移变形。     

Q460C钢的连续冷却转变曲线

研究了Q460C钢连续冷却过程中奥氏体转变过程以及转变产物的组织变化,为制定生产工艺提供参考依据。由Q460C钢的连续冷却转变曲线(CCT图)和不同冷却速率的显微组织可知,当冷却速率较低时,形成粗大的块状铁素体和珠光体;当冷却速率大于3℃/s时出现贝氏体,形态似针状铁素体,其形成温度在450~600℃;当冷却速率大于15℃/s时,发生马氏体转变,马氏体的转变点约为350℃。     

Ti-4.4Al-3.8Mo合金的亚稳相变及其对硬度的影响

对锻态 Ti-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.     

退火温度对冷轧Ti-13V-3Al-0.5Cu形状记忆合金组织结构与马氏体相变的影响

使用XRD、TEM、DSC和室温拉伸等分析测试手段,对冷轧后经不同退火温度处理的Ti-13V-3Al-0.5Cu(%,原子分数)合金微观组织结构,马氏体相变行为,力学性能和形状记忆性能进行了研究。经冷轧、退火处理后,合金在室温下的组织主要为α"马氏体相,存在少量残余β母相、α相和Ti₂Cu第二相。随着退火温度的增加,合金形状记忆性能先升高后降低;当退火温度为750℃时,在预应变量为6%的前提下可实现5.3%的可回复应变。其组织结构观察结果表明,经冷轧、退火处理后,合金中α"马氏体形貌由“V”字型自协作组态向择优取向的单一取向马氏体板条转化,界面可动性提升,马氏体临界再取向应力降低,形状记忆性能提高。     

基于α'组织设计适于激光立体成形的新型高塑性Ti-4.13Al-9.36V合金

为了提高Ti-6Al-4V合金的加工硬化率和塑性,基于其团簇成分式12[Al-Ti₁₂](AlTi₂)+5[Al-Ti₁₄](V₂Ti)设计成分式为4[Al-Ti₁₂](AlTi₂)+12[Al-Ti₁₄](V₂Ti)的(Ti-4.13Al-9.36V, %)合金,采用激光立体成形工艺制备Ti-4.13Al-9.36V和Ti-6.05Al-3.94V(对比合金),研究了沉积态和固溶温度对其显微组织和力学性能的影响。结果表明,沉积态Ti-4.13Al-9.36V和Ti-6.05Al-3.94V合金的显微组织均由基体外延生长的初生β柱状晶和晶内细小的网篮α板条组成。Ti-6.05Al-3.94V合金的初生β柱状晶的宽度约为770 μm,α板条的宽度约为0.71 μm;而Ti-4.13Al-9.36V合金的初生β柱状晶的宽度显著减小到606 μm,α板条的宽度约为0.48 μm。经920℃固溶-淬火处理后Ti-6.05Al-3.94V样品的显微组织为α'+α相,其室温拉伸屈服强度约为893 MPa,抗拉强度约为1071 MPa,延伸率约为3%。经750℃固溶-淬火处理后Ti-4.13Al-9.36V样品的显微组织为α'+α相,与α'马氏体相比,应力诱发的α'马氏体能显著地提高合金的加工硬化能力,其室温拉伸屈服强度约为383 MPa,抗拉强度约为 989 MPa,延伸率达到了17%。这表明,根据团簇理论模型调控α'+α的显微组织能有效提高激光立体成形Ti合金的加工硬化能力和塑性。     

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．     

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.……     

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.     

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.     

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 ...