添加Sn对不同Mg/Si比Al-Mg-Si合金时效硬化和析出行为的影响

采用硬度测试和透射电镜研究Sn对不同Mg/Si比Al-Mg-Si合金时效硬化与析出行为的影响。结果表明：添加Sn虽然增加了低Mg/Si比合金峰值时效的析出相密度，但也降低了β″相的析出速度，从而降低了低Mg/Si比合金峰时效前的硬化速度和峰时效硬度。过时效阶段，含Sn合金的高析出相密度提高了低Mg/Si比合金过时效硬度。对于高Mg/Si比合金，添加Sn不仅增加合金的析出相密度，同时也提高了β″相的析出速度，从而增加了合金的硬化速度和峰时效硬度。     

残余形变对莫来石短纤维/Al-4.5Cu复合材料及其基体合金时效析出行为的影响

用挤压铸造法制备莫来石(mullite)短纤维/Al-4.5Cu复合材料及其基体合金。用硬度测试(HB)、差示扫描量热仪(DSC)和透射电镜(TEM),研究固溶淬火后残余形变(0 %,12.5 %,25 %,34.4%)和纤维对复合材料及其基体合金时效析出行为的影响。结果表明:形变对Al-4.5Cu合金的时效析出过程具有十分明显的加速作用,随着形变度增加,时效加速作用进一步加强;莫来石短纤维对Al-4.5Cu合金的时效析出过程具有加速作用;纤维和形变同时存在时,复合材料的时效析出过程还会进一步加快。但是,形变或/和纤维抑制了Al-4.5Cu合金中GP区的形成。     

亚微米Al2O3P/Al-Mg-Si复合材料时效行为

为了研究亚微米级Al₂O₃颗粒对基体合金时效过程的影响规律,在 6061 铝合金基础上调整Mg、Si含量,采用压力浸渗法,制备了Al₂O₃体积分数为30%的亚微米级Al₂O_3P/Al-2.26Mg-0.63Si复合材料。通过硬度试验、SEM和TEM等手段,研究了复合材料及其基体合金的时效行为。结果表明,Al-2. 26Mg-0.63Si 合金的时效过程比较明显,随时效温度的提高峰时效时间提前,190℃时出现时效软化现象。亚微米Al₂O₃颗粒的加入强烈抑制复合材料的时效过程,时效曲线未出现明显时效峰。分析认为,由于大部分Mg 元素被消耗在界面形成MgAl₂O_4,且基体中位错稀少,不利于溶质原子扩散,因此复合材料中沉淀相在过时效阶段仍停留在GP区状态,没有充分长大,时效析出受到抑制。     

SiCw／7475Al复合材料时效硬化研究

通过硬度测试，结合ＤＳＣ曲线，对ＳｉＣｗ／７４７５Ａｌ复合材料的时效析出过程进行了研究。结果表明，与基体合金相比，复合材料的时效硬化效果较代，最佳人工时效温度提高，析出过程稍有延缓，分析认为，该复合材料时效特征与增中相引入的高密度位错，析出相与基体位错的相互作用有密切关系。     

时效对Mg-Y-Nd合金的影响

研究了Mg-Y-Nd合金时效过程中的硬化软化现象．在时效初期(-473K／2h左右)出现了一次明显的时效硬化峰，之后硬度急剧下降；然后合金的硬度缓慢增加，出现小幅二次硬化现象；523K／600h后，合金出现软化现象微观结构的分析结果表明，初次时效峰是合金中析出了5nm大小的MgY弥散分布沉淀相所致；随后弥散相溶解消失，材料出现软化；在时效过程中β沉淀相的析出、增多和板条状组织的形成导致材料二次硬化．长时间时效后β沉淀相的聚集长大，以及在α／β界面产生纳米晶MgO区导致材料再次软化。     

Al-Mg-Si-RE合金的淬火敏感性研究

用硬度损失法测定了Al—Mg—Si—RE合金的TTD曲线。指出:高温形变加速固溶体淬火冷却时的析出过程,含金时效硬化效果对淬火冷却速度有较高的敏感性。高温形变直接淬火冷却的喷水温度应≤50℃,才可保证获得均匀细小的GP区和高的时效硬化效果。     

Si对Al-Mg-Cu合金时效析出行为的影响

向不同镁含量的Al-Mg-Cu合金中添加Si元素,研究Si对该合金时效强化行为的影响,并在此基础上探究自然时效处理对合金后续人工时效行为的影响.研究结果表明,在2.0％Mg的基础上添加0.15 wt％Si可以显著增强合金的人工时效强化效果,但是合金强度随Si含量的进一步增加而增加的幅度较小;Si对合金的时效强化效果是由于Si使得合金中的时效析出相明显细化且分布弥散.添加0.15％S i的合金在经过自然时效后再进行人工时效(简称双时效),经双时效后的人工时效前期的硬度值高于直接人工时效的硬度值,但两种时效工艺峰值硬度基本相同;然后若继续增加Si含量,合金经双时效后的硬度峰值低于直接人工时效所得的硬度值.     

碳化硅晶须和颗粒增强铝基复合材料的时效行为EI

综述了近年来碳化硅晶须（ＳｉＣｗ）和碳化硅颗粒（ＳｉＣｐ）增强铝基复合材料（ＳｉＣｗ（ｐ）／Ａｌ）时效行为的研究发展状况。主要包括碳化硅晶须与颗粒对基体时效硬化动力学、基体沉淀脱溶过程的影响规律和作用机制，以及影响ＳｉＣｗ（ｐ）／Ａｌ复合材料时效特性的因素。     

微量Mg元素添加对Cu-Cr合金析出行为及性能的影响

通过熔炼铸造工艺制备了Cu-Cr和Cu-Cr-Mg合金,评价了Mg元素对Cu-Cr合金硬度、导电和抗软化性能的影响,研究了Mg元素对Cu-Cr合金析出相的细化作用,探讨了Mg元素的迁移行为。结果表明,相比于Cu-Cr二元合金,时效态Cu-Cr-Mg合金具有更高的硬度和软化温度,且保持较高的导电性能。两种合金的主要时效强化相均为纳米Cr析出相,Mg元素的加入抑制了纳米沉淀相的长大和结构转变,峰时效态Cu-Cr-Mg合金的析出相与基体可能仍保持共格界面关系,过时效态合金中出现与Heulser相结构相同的析出相,且峰时效态Cu-Cr-Mg合金经过高温保温处理后,其强化相的尺寸明显小于Cu-Cr合金析出相。EDS的结果表明,在时效初期Mg和Cr共存于析出相内部,而在时效后期析出相内部只有Cr元素存在,Mg元素发生迁移,同时理论估算结果显示,Mg元素可明显降低Cu(fcc)/Cr(bcc)之间的界面能,导致其偏聚于基体/析出相界面处,这可能是Mg元素能够细化析出相和提高合金性能的主要原因。     

SiCw／Al—Li复合材料的热处理强化效应

本文系统地探讨了热处理工艺对ＳｉＣｗ／Ａｌ－Ｌｉ复合材料的时效强化特性的影响。研究表明，ＳｉＣ晶须的加入显著加速了Ａｌ－Ｌｉ合金的时效析出过程，在１９０℃时效条件下，ＳｉＣｗ／Ａｌ－Ｌｉ复合材料在６ｈ就已达到峰值时效，提高固溶温度可以增加复合材料的峰值时效硬度，而增加固溶时间对峰值硬度无明显的影响。     

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.……     

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.     

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.     

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.