贝氏体区等温时间对TRIP钢残奥及力学性能影响

为研究贝氏体区等温时间对热轧TRIP钢残余奥氏体和力学性能的影响,采用金相显微镜、X射线衍射、拉伸实验等方法对3种不同贝氏体区等温时间下制备的热轧TRIP钢进行分析.结果表明:随着贝氏体等温时间的延长,残余奥氏体量减少而残余奥氏体碳含量增加,残余奥氏体晶粒尺寸及残余奥氏体形貌变化不大;热轧TRIP钢的力学性能随着贝氏体...     

TRIP钢板在单向拉伸变形下的相变行为研究

TRIP钢的塑性取决于残余奥氏体的含量及其相变速度.研究TRIP钢中残余奥氏体在单向拉伸变形下的相变行为,首先回顾了TRIP钢板的研究进展,然后对一种低碳硅锰系TRIP700钢板在单向拉伸变形下的力学性能和相变性能进行了试验研究,并用扫描电镜方法分析了该TRIP钢在变形过程中微观组织的变化.结果表明,该低碳硅锰系TRIP钢板兼有高强度和高韧性的特点,在单向拉伸变形中残余奥氏体的含量与等效应变的关系可用来logfγ0-logγ=kε.表示.     

新型热轧低碳TRIP 钢的轧制工艺与疲劳性能

对比研究了现场不同工艺所得碳锰系车轮用钢及低碳低硅含磷铬系相变诱发塑性(TRIP)钢的力学性能、微观组织、疲劳性能和疲劳断口。结果显示,较传统碳锰系车轮用钢,新型TRIP钢具有相当的屈服强度,抗拉强度明显提高了100~150 MPa,疲劳极限提高了50~140 MPa。疲劳极限随抗拉强度的提高有增大趋势。铁素体、贝氏体、残余奥氏体组织较铁素体、贝氏体、珠光体组织和铁素体、珠光体、马奥岛组织具有更好的疲劳性能。     

强塑积大于30 GPa%的热轧中碳TRIP钢组织及性能研究

为研究贝氏体相变温度对中碳热轧TRIP钢组织与性能的影响,采用扫描电镜(SEM)、X射线衍射(XRD)与高分辨透射电镜(HRTEM)对含Ti与Mo的中碳热轧TRIP钢进行了显微组织观察、残余奥氏体含量测定以及析出相的表征与分析.结果表明:在400℃贝氏体相变温度下,试验钢的残奥含量与强塑积均达到最大值,分别为28.2%和31.14 GPa·%;同时在钢中发现了呈块状、无规则形状以及片层状形貌分布的残余奥氏体,对衍射斑标定后显示,片层状残余奥氏体与铁素体基体同时满足kurdjumov-Sachs(K-S)与Nishiyama-Wasserman(N-W)位向关系;HRTEM分析显示,Mo可以溶入TiC而生成(Ti,Mo)C粒子,而纳米级的(Ti,Mo)C粒子可以显著提高钢的沉淀析出强化效果.     

热轧TRIP钢残余奥氏体及其稳定性研究

采用X射线衍射(XRD)、透射电镜(TEM)和拉伸实验等方法,研究三种工艺制备的热轧TRIP钢残余奥氏体及其碳含量和稳定性.结果显示:贝氏体区停留时间对残余奥氏体量影响较大,当在贝氏体区模拟卷取时,残余奥氏体量最多;适当的增加弛豫时间,会增加最终组织中残余奥氏体的碳含量;残奥碳含量,还有残余奥氏体的形状和晶粒大小及周围...     

汽车用高强度TRIP钢组织性能及成形工艺

概述了高强度TRIP钢对汽车轻量化的作用及TRIP钢的显微组织对其性能的影响,探讨了铁素体、贝氏体、残余奥氏体的含量对TRIP钢性能的影响规律,以及设备、模具和成形工艺参数的选择原则。结果表明,TRIP钢中铁素体可以提高铜的塑性,贝氏体可以提高强度和韧性,而当残余奥氏体的体积分数大于8％时,产生TRIP效应,并提高了钢的综合性能;以上组织的获得,应在成形时控制成形设备的能量、栽荷、速度、时间等工艺参数。     

高强贝氏体基体钒微合金化TRIP钢的性能

对一种钒微合金化TRIP钢进行冷轧连续退火,研究了钢的组织特征和力学性能。结果表明,贝氏体基TRIP钢的组织由贝氏体/马氏体和少量的残余奥氏体组成。随着贝氏体区等温时间的延长,钢的抗拉强度下降,屈服强度和延伸率提高。残余奥氏体由块状向薄膜状转变,体积分数增加,薄膜状残余奥氏体主要分布在贝氏体板条间,厚度为50-90 nm。在400℃等温180 s连续退火钢板呈现出相对低抗拉强度(960 MPa)、高屈服强度(765 MPa)和高延伸率(22.0%)的特性,而且加工硬化指数(0.20)、各向异性指数(0.94)和强塑积(21120 MPa.%)也较为优良。     

温轧工艺对纳米贝氏体相变速率、组织和力学性能的影响

采用温轧加等温热处理工艺制备纳米贝氏体钢,研究了形变温度对纳米贝氏体相变速率的影响。结果表明,形变过冷奥氏体在503 K的贝氏体等温转变时间由常规等温淬火的50 h缩短至20 h,纳米贝氏体钢的抗拉强度为2127 MPa、延伸率为4%。在实验温度范围内进行的过冷奥氏体形变均能促进纳米贝氏体相变,相变速率随着形变温度的降低而提高。过冷奥氏体形变量大于30%后残余奥氏体组织明显细化,块状残余奥氏体全部转变为薄膜状。温轧工艺可在不恶化其它力学性能的前提下加速低温贝氏体相变,从而缩短热处理时间使生产成本降低。     

热轧钒微合金TRIP钢的微观组织和力学性能

对一种钒微合金TRIP钢进行了热轧试验,并研究其微观组织特征及力学性能.结果表明,将终轧温度控制在Ae3附近,热轧后的钒微合金TRIP钢具有由铁素体,粒状贝氏体和一定量残余奥氏体组成的复相组织.EBSD分析结果表明,其中75%以上的铁素体晶粒尺寸在l-6 μm;绝大多数晶界取向差角度位于29°-60°.当终轧温度为83...     

等温淬火对纳米贝氏体钢的组织和力学性能的影响

依据Thermo-Calc计算设计了一种成分为Fe-0.8C-2Mn-1.5Si-1.5Cr-0.25Mo-0.25Ni-1Al-0.25Co-0.1V可用于制造钢丝的纳米贝氏体钢,使用热膨胀相变仪、扫描电镜(SEM)、X射线衍射(XRD)、透射电镜(TEM)和拉伸实验等手段研究了等温淬火温度和时间对其组织和力学性能影响。结果表明：这种纳米贝氏体钢低温等温淬火后的组织,由纳米结构的贝氏体铁素体板条、残余奥氏体和少量的马氏体组成。随着等温淬火温度的提高相变速率随之提高,贝氏体铁素体的体积分数增大。随着等温淬火时间的延长,贝氏体铁素体的体积分数增大而过冷奥氏体的量减少,在室温下生成的块状M/A岛的尺寸减小和体积分数降低,碳的配分使过冷奥氏体的稳定性提高,M/A岛中的脆性马氏体比例大幅度降低,拉伸断口由混合型断裂向准解理断裂转变。将这种钢在230℃保温48 h后强塑性匹配最佳,其抗拉强度和屈服强度分别达到1625和1505 MPa,延伸率达到34.5%。     

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...     

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.     

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.     

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.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

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.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.