退火温度对GH3600合金箔材组织与性能的影响

目的 探究退火温度对GH3600镍基高温合金箔材微观组织及力学性能的影响。为制备综合性能良好的GH3600箔材提供参考。方法 将厚度为2 mm的铸态板材反复轧制退火得到组织均匀的0.3 mm厚度带材,再利用四辊冷轧机将带材轧制成厚度为0.1 mm和0.05 mm的箔材,然后将2种厚度箔材在950、1 000、1 050 ℃下保温1 h后空冷。通过金相观察、电子探针、EBSD检测及XRD分析来研究箔材的微观组织演变。通过拉伸实验检测箔材的室温拉伸性能。结果 随着变形程度的增大,轧制态箔材晶粒沿轧制方向被拉长得更加明显。在相同热处理参数下,0.05 mm退火态箔材晶粒尺寸更小。退火后,箔材晶粒发生了回复再结晶并析出了细小的碳化物。随着退火温度的升高,晶内碳化物逐渐减少,孪晶界比例增大,再结晶程度及晶粒尺寸增大。0.05 mm箔材在1 050 ℃退火时,其晶粒迅速粗化,在厚度方向上出现单层晶,导致箔材的抗拉强度及延伸率出现异常降低的现象,即“越小越弱”的尺寸效应。结论 适宜的热处理工艺有助于改善箔材的微观组织,进而提高其力学性能。0.05 mm箔材在950 ℃下退火1 h时,其延伸率为19.1%,屈服强度以及抗拉强度分别达到293 MPa和560 MPa,综合力学性能良好。     

TA1纯钛微型杯件软模微拉深成形工艺研究

目的 提高现有微成形工艺的可成形性,解决薄板易破裂等缺陷,探究薄板软模微拉深成形工艺的工艺参数对成形性的影响,致力于制造具有更大拉深比的微型杯件。方法 采用退火后的纯钛薄板作为原始板材,设计了薄板的软模微拉深成形模具进行实验。实验中探讨了工艺参数和材料参数对微型杯件极限拉伸比的影响。工艺参数包括压边力、橡胶性能和润滑方式,材料参数主要是晶粒尺寸。结果 通过控制压边力能够避免微拉深工艺中的缺陷。压边力过低会导致法兰区域起皱,压边力过高会导致上圆角部位破裂。采用刚度系数为72N/mm的压边弹簧能够有效避免起皱和破裂。选用硬度为65HA的聚氨酯橡胶能够成形出极限拉深比最大（为2.64）的纯钛微型杯件。软模微拉深工艺必须采用有效的润滑方式来提高板材的流动行为。采用蓖麻油润滑能够有效避免微型杯件的破裂缺陷。板材的晶粒尺寸对极限拉深比的影响是最强烈的。晶粒尺寸为8.4μm的纯钛薄板能够制造出极限拉深比为2.64的微型杯件,而随着晶粒尺寸的增大,微型杯件的极限拉深比显著下降。结论 通过软模微拉深工艺并且采用合适的工艺参数成功制备了极限拉深比为2.64的微型杯件,与现有工艺相比,所获得的微型杯件的极限...     

镁合金笔记本电脑外壳的温成形技术研究

采用0.6mm厚的AZ31镁合金材料,以温成形方式获得了复杂外形尺寸的笔记本电脑外壳.通过研究温度对AZ31镁合金板料拉深成形性能的影响发现:180～280℃成形的镁合金电脑外壳零件不会出现断裂和起皱缺陷,但角部高度随成形温度的升高而增加;低于180℃成形,零件圆角出现褶皱;高于280℃成形,圆角被拉裂;并且成形速度和摩擦也会影响零件成形.     

台阶盒形件起皱和开裂改善

目的 改善台阶盒形件拉深成形时凸缘区起皱和圆角区开裂的缺陷。方法 理论分析了起皱和开裂产生的原因,利用有限元模拟分析了压边力大小、凹模运行方式和板料形状对台阶盒形件拉深成形的影响,采用实验验证了有限元模拟结果的准确性。结果 长方形板料拉深成形时,4个角部相比直边部位流动阻力更大,直边部位材料过度向模具型腔内流动,造成凸缘区周向压应力过大,进而引起起皱,当零件拉深深度较大时,圆角部位材料变形剧烈且材料流动不均匀,极易产生开裂;采用20 kN的压边力、梯形的凹模向下运行方式和类椭圆形板料的工艺参数可以控制材料流动,使板料变形均匀并改善凸缘区起皱和圆角区开裂缺陷。结论 有限元模拟可为冲裁工艺参数的选取提供理论指导。     

镁合金塑性成形性能实验与数值模拟研究

对ME20M镁合金板料进行了热拉深成形性能实验与数值模拟.研究表明,ME20M镁板热拉深成形极限高度随实验参数的不同而不同,其塑性成形性能随温度的升高明显改善;数值模拟可以很好地预测不同实验参数下镁合金板料热拉深成形极限的高度.对热拉深成形件传力区部位进行金相实验得知,合理控制热拉深实验参数能保证镁合金塑性成形件微观组织,进而保证成形件质量.     

温度对ZK60镁合金细晶板材成形性能的影响

研究了温度对ZK60镁合金细晶板材成形性能的影响。通过单向拉伸试验研究了ZK60细晶板材在25～300℃下的拉伸成形性和力学性能各向异性,进而通过杯突试验和热拉深试验研究了温度对板材成形性能的影响。研究结果表明:随着温度的升高,板材的各向异性逐渐降低,在300℃下的断裂伸长率在341%以上。ZK60细晶板材的成形性能随着温度的升高显著提高,在本实验条件下,当温度为250℃时获得最大的Erichsen值(IE=18. 7 mm)和最大的极限拉深比(LDR=1. 8),ZK60镁合金细晶板材的最佳杯突成形温度范围为200～250℃,最佳热拉深成形温度范围为250～300℃。     

钛/铁复合板平底球形薄壁件充液拉深工艺研究

目的 选用充液拉深先进成形技术制备钛/铁复合板平底球形薄壁件,并研究其充液拉深变形行为,以解决传统拉深工艺制备平底球形薄壁件极易产生褶皱的问题。方法 对钛/铁复合板平底球形薄壁件在不同液压力、压边间隙及凸模与板料间摩擦因数等工艺参数下的充液拉深过程进行数值模拟。对数值模拟结果进行分析,讨论工艺参数对零件成形性能的影响以及抑制起皱的机理。最后在不同拉深工艺下进行成形试验,制备钛/铁复合板平底球形薄壁件并与数值模拟结果进行对比。结果 数值模拟和成形试验结果表明,传统拉深工艺制备的钛/铁复合板平底球形薄壁件出现了明显的褶皱,采用充液拉深工艺可以有效解决零件侧壁起皱的问题。增大液压力、减小压边间隙或增大凸模与板料间摩擦因数会导致零件减薄率的提高并降低零件侧壁起皱的风险。在压边间隙1.5 mm、液压力25 MPa的条件下,采用充液拉深工艺可以制备出侧壁无褶皱的平底球形薄壁件。结论 通过充液拉深工艺可以有效解决钛/铁复合板平底球形薄壁件成形过程中起皱的问题。     

GH648合金的热处理适应性

通过对GH648合金在不同热处理后的力学性能及显微组织进行试验研究,获得了GH648合金制零(组)件热处理工艺的可行性评价,从而达到确保零(组)件产品质量的目的。结果表明:GH648合金棒材经950℃渗铝处理、850℃长时除应力处理,板材经1 050℃或950℃短时退火处理,其力学性能均满足规定要求,零(组)件热工艺可行。     

轧制单层晶铜箔滑移启动和应变局部化的晶体塑性模拟

在晶粒尺度采用晶体塑性有限元模拟极薄带材轧制成形过程,对优化和改进材料模型以及探究极薄带材塑性变形机制具有重要作用.箔材轧制成形性能主要依赖材料的微观结构(晶界、滑移系、取向).采用退火态的单层晶铜箔为原料,进行箔轧实验和晶体塑性有限元模拟.建立反映晶粒形貌、晶界和取向各向异性的单层晶铜箔晶体塑性有限元模型,分析极薄带轧制成形中单/多滑移系启动状态和应变局部化现象.为准确构建晶体塑性有限元模拟的初始晶粒结构,消除微观组织亚表面的影响,采用垂直晶界即在厚度方向上建立只有一层晶粒的铜箔晶粒模型.结果表明:晶粒各向异性影响单层晶铜箔的轧制变形机制;晶界处的变形和滑移系运动状态完全不同于晶粒其他位置;单层晶轧制变形的滑移状态表现出明显的各向异性,出现局部滑移带和应变局部化,随轧制变形量的增大,滑移差异显著增大;晶界两侧局部区域存在滑移和变形的显著差异,这为亚晶和微观裂纹源的形核提供了有利的位置.     

AZ31薄板热拉深工艺研究

为提高AZ31薄板热拉深质量、确定热拉深过程的合理工艺参数,选取不同的成形温度、模具间隙及凸模圆角半径,拉深成形了AZ31试样,采用KH-2200MD金相显微镜观察其内部组织变化,并通过x-ray衍射实验分析晶面取向的变化.实验结果表明,0.8mm的AZ31B镁合金板料在240℃附近的成形性能最好,拉深后材料组织晶粒大小均匀,晶面取向分布均匀.热拉深AZ31B镁合金板料应将凸、凹模间隙选为1.1倍的板料厚度.在压边力不变的条件下,随着凸模圆角半径的减小,拉深高度降低加快,并且起皱现象加重.     

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.     

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...     

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.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

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.……     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

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.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.