SiCp/Al复合材料搅拌铸造新型搅拌器流场及工艺研究

SiCp/Al复合材料搅拌铸造法虽然具有制备成本低、近终成型的优点,但是实现SiC颗粒在铝合金熔体的均匀分散难度很大,这与搅拌器结构及搅拌工艺有直接关系。采用数值模拟和实验相结合的方法开展了新型桨栅复合搅拌器设计及其工艺研究,比较了桨栅复合搅拌器与单一搅拌器的流场结构和速度场分布,并在此基础上进行了搅拌铸造工艺研究。结果表明:(1)桨栅复合搅拌器能够较好地实现复合材料大体积熔体的均匀搅拌和高速剪切,复合搅拌器内熔体的流场为较好的轴向和径向循环,液面更为平稳,搅拌转速500r/min时熔体最大速度为3.9m/s,流场结构和剪切速度均优于单一形式搅拌器;(2)用桨栅复合搅拌器进行20%(质量分数)SiCp/A357复合材料搅拌铸造工艺实验,在搅拌温度610℃、搅拌转速500r/min、搅拌时间20min的工艺条件下,SiC颗粒分布均匀且无气孔缺陷。     

SiCp增强泡沫铝制备工艺研究

对熔体发泡法制备SiCp增强泡沫铝基复合材料的制备工艺进行了探索，通过正交试验研究了SiC的粒度、发泡剂TiH2的加入量、发泡温度、保温时间等工艺参数对泡沫铝孔隙率及孔结构的影响，确定了制备SiCp增强泡沫铝基复合材料的最佳工艺参数：掺入10％（质量分数）1000目的SiC颗粒增粘，在发泡剂TiH2加入量为2％（质量分数），搅拌时间2min，保温温度700℃以及保温时间3min的工艺条件下，制得的泡沫铝的孔隙率达到80％，平均密度达到了0．5g／cm^3，且基本没有无泡层。最后对泡沫铝的产业化生产的可行性作了讨论。     

粉煤灰颗粒增强铝基复合材料的研究与进展

粉煤灰颗粒增强铝基复合材料因低廉的价格与优异的性能日益受到人们关注.介绍了粉煤灰颗粒增强铝基复合材料常用的制备方法(搅拌铸造法、压力浸渗法以及粉末冶金法);指出了各种制备工艺的优缺点;阐述了粉煤灰颗粒增强铝基复合材料优良的性能,特别是其力学性能、耐磨性能、阻尼性能与电磁屏蔽性能;展望了粉煤灰颗粒增强铝基复合材料的发展趋势.     

粉末冶金法制备铝基复合材料的研究

论述了铝基复合材料研究和发展的概况,简要介绍了非连续增强铝基复合材料常用的几种制备方法,包括挤压铸造法、原位反应法、搅拌铸造法和粉末冶金法等,并重点针对粉末冶金法做了系统的阐述,包括这种方法的优势、具体的制备工艺、材料性能的影响因素及研究进展等。最后,展望了粉末冶金法进一步用于制备非连续增强铝基复合材料的前景。     

表面镀铝及附着碳化硅微粒的高模碳纤维与铝的压铸复合特性

采用挤压铸造法直接制备了高模碳纤维、离子喷镀铝碳纤维及附着SiC微粒的碳纤维增强铝复合材料,考察了碳纤维与铝的压铸复合特性。结果表明,纯碳纤维和喷镀1μm铝层的碳纤维与铝的压铸复合持性差,而且镀铝碳纤维的铝镀层预热时发生氧化,形成氧化物界面层,但附着SiC微粒的碳纤维与铝的压铸复合特性好,纤维在铝基体中均匀分散,被铝浸润,纤维与纤维无相互接触。实验初期制备的复合材料的轴向拉伸强度为600MPa。SiC微粒的主要作用是间隔纤维,形成利于熔融铝浸透纤维的通道,使铝与纤维能较好地复合。     

玻璃/铝基废弃物复合材料搅拌流场的模拟

运用流体软件Fluent对采用机械搅拌法制备的玻璃/铝基废弃物复合材料流场进行模拟,采用MRF动参考系模型、多相流Mixture混合模型及标准k-ε模型,模拟使用三层正交组合轴流搅拌桨产生的流场。结合搅拌工艺特点对模拟的结果进行了分析,通过分析搅拌槽的宏观流场、轴向速度和径向速度分布,定性指出了各区域搅拌混合的效果,并同其它搅拌桨产生的流场进行了比较。     

真空搅拌铸造制备SiC颗粒增强ADC12铝基复合材料及其力学性能表征

以SiC/Cu复合包裹粉体为增强相,采用真空搅拌铸造技术制备SiC/ADC12铝基复合材料,研究制备工艺条件对复合材料力学性能的影响,同时借助X射线衍射(XRD)和扫描电子显微镜(SEM)等测试分析手段对其物相结构进行表征。结果表明:SiC/Cu复合粉体显著改善了SiC颗粒在熔融铝合金基体中的润湿性和分散性。当搅拌温度为580℃,搅拌时间为30min,复合粉体添加量为4%(质量分数)时,复合材料获得最佳的力学性能,拉伸强度283MPa,硬度HB133,较基体合金分别提高24.1%和77.3%,较普通SiC增强复合材料提高15.5%和26.7%。     

颗粒增强铝基复合材料制备方法及研究现状

简单介绍了颗粒增强铝基复合材料的强化机理,重点概述了颗粒增强铝基复合材料的制备方法及其研究现状,包括搅拌铸造法、液态金属浸渗法、喷射沉积法、粉末冶金法、原位合成法,并总结了各自的优缺点,最后提出了颗粒增强铝基复合材料的研究趋向。     

Al2(SO4)3反应在制备铝基复合材料中的应用

对传统搅拌铸造法制备铝基复合材料的颗粒加入方式进行改进,采用直接加入Ａｌ２（ＳＯ４）３,由其反应分解产生Ａｌ２Ｏ３原位合成铝基复合材料;由Ａｌ２（ＳＯ４）３分解的ＳＯ３可以对熔体进行精炼、除气;结果表明,Ａｌ２Ｏ３颗粒和基体结合良好,没有发现气孔团聚、集聚、偏析,克服了传统搅拌铸造所带来的铸造缺陷。     

超声铸造铝基复合材料研究

一、前言 非连续增强铝基复合材料具有比模量、比强度高,耐磨损,热膨胀系数低等特点,并可用常规的加工技术进行制备,受到了材料科学界的重视,相继开发出粉末冶金,挤压铸造,流变铸造、液相铸造、喷镀沉积,爆炸复合等多种复合技术,以满足工业技术领域的不同需求。其中,增强相直接加入铝液中的液相铸造技术有成本低、工艺简便的显著特点,可广泛地推广应用。近年来,各国在理论或技术上仍继续进行研究,以进一步提高铸造复合材料性能。众所周知,提高铸造复合材料性能必须改善陶瓷增强相与铝液的润湿性,提高增强相在铝基体中分布的均匀性,抑制增强相与铝合金间的化学反应以及降低气孔率。同时,铸造复合材料的重熔性也是实现应用的重要性能之一。 对液相铸造法制备非连续增强铝基复合材料进行研究过程中,应用超声波对铝液进行振荡可以缩短增强相与铝液润湿所需要的时间,明显改善增强相在铝基体中的分布均匀性,减少气孔率,显著提高了铸造复合材料的质量。早期P.K.Rohatgi曾报道过超声可改善增强相在液金属中的润湿性,但未见到详细的研究报道。本文对超声铸造法制备铝基复合材料过程的特点,显微组织特征,断口形貌及重熔性等进行了初步的探讨。     

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.     

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.