中锰Q&P钢残余奥氏体的稳定性及其TRIP效应

通过单向拉伸及平面应变实验研究了Mn含量为7%的中锰淬火-配分(QP)钢残余奥氏体的机械稳定性,利用X射线衍射仪(XRD)测定试验钢残余奥氏体的含量,通过观察试验钢的拉伸曲线及扫描电镜(SEM)、透射电镜(TEM)照片,分析变形前后的微观组织,研究中锰QP钢的变形机制。结果表明:应力状态对残余奥氏体稳定性有较大的影响,平面应变更有利于相变诱导塑性(TRIP)效应的发挥;中锰QP钢的拉伸变形特征是由超细晶硬化机制和TRIP效应相互作用产生的,通过微观组织观察发现中锰QP钢的塑性变形主要是残余奥氏体的TRIP效应,其中薄膜状的残余奥氏体的稳定性最高。     

低硅含铝TRIP钢残余奥氏体变形过程中稳定性研究EI北大核心CSCD

采用预拉伸实验对低硅含铝TRIP钢变形过程中残余奥氏体的演变规律进行研究,建立残余奥氏体变形过程中稳定性与加工硬化指数n之间的对应关系,在此基础上通过设计不同热处理工艺,获得具有不同初始残余奥氏体特性的TRIP钢以及具有不同组织构成的TRIP钢,并分析了TRIP钢的残余奥氏体稳定性。结果表明:TRIP钢中的残余奥氏体随着变形的深入,稳定性逐渐增加;残余奥氏体越稳定,TRIP钢的瞬时加工硬化值越稳定(n值越稳定);随着初始碳含量的增加,残余奥氏体在变形过程中的稳定性也随之提高。在变形过程中,残余奥氏体的稳定性受残余奥氏体碳含量,分布以及周围相等因素的共同影响。     

热轧TRIP钢组织性能的研究

采用实验室热轧机对高硅和低硅TRIP钢(A钢和B钢)进行控制轧制试验,研究了热轧后等温淬火对热轧TRIP钢组织性能的影响.通过显微组织观察,力学性能分析,探讨了两种钢的应变诱导相变和相变诱发塑性行为.研究表明:A、B钢均能够获得铁素体、贝氏体和大量稳定残余奥氏体的混合组织,具有较高的力学性能;残余奥氏体稳定性是提供TRIP的重要因素,B钢中贝氏体和残余奥氏体较多,相变诱发塑性效果更好,其性能优于A钢;等温时间影响热轧TRIP钢的力学性能,随等温时间的延长,A、B钢的伸长率增加,等温时间超过120 min,导致碳化物析出,残余奥氏体的稳定性降低;B钢经热轧后在400 ℃等温25 min,抗拉强度和伸长率分别达到了784 MPa和36%的最高值.     

Q＆P钢塑性变形机制及组织-性能研究

研究淬火和碳再分配(Q&P)热处理工艺对低碳硅-锰系Q&P钢的显微组织及精细结构的影响,并和常规工艺实验进行对比.通过SEM,TEM分析,经Q&P工艺热处理后的钢板可获得板条马氏体和残余奥氏体两相组织,残余奥氏体呈膜状.利用XRD技术并结合软件编程的手段对残余奥氏体进行了定量分析.采用MTS万能拉伸机测定了其力学性能并进行了断口观察,拉伸试样纤维区为比较典型的韧窝状形貌,体现出良好的韧性断裂特征.结果表明:Q&P工艺处理后的钢板具有高的抗拉强度(1000MPa以上)和良好的塑性,残余奥氏体在组织中起到了相变诱发塑性的作用.     

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。     

Mn含量对低碳中锰TRIP钢组织性能的影响

为研究连续退火工艺生产中锰TRIP钢汽车板的可行性,采用CCT-AY-Ⅱ型钢板连续退火机模拟分析了不同锰含量对中锰TRIP钢组织性能的影响规律.采用SEM、TEM和EBSD等微观分析方法观察不同锰含量中锰TRIP的微观组织,利用XRD法测量了残留奥氏体量,实验测量其力学性能.结果表明:试验钢在650℃保温3 min时,随着锰质量分数(4.8%≤w(Mn)≤8%)的增加,屈服强度先增加后降低,抗拉强度持续升高,断后延伸率则基本不变,维持在20%左右,残余奥氏体含量也随着锰含量的增加而增加;当锰质量分数超过6%(含6%)时,真实应力-应变曲线由于动态应变时效而呈锯齿状,且加工硬化指数远大于5Mn钢.试验钢的高塑性由亚稳奥氏体的TRIP效应和超细晶铁素体或马氏体共同提供.     

TRIP钢的动态拉伸变形行为研究

在气动式间接杆杆型冲击拉伸试验机上对二种TRIP钢的拉伸性能随应变率的变化进行了研究,对强度随应变率的变化以及断口形貌和孔洞与变形的关系进行了分析.研究结果表明:TRIP钢在所研究的应变率范围对应变率是敏感的,屈服强度和抗拉强度随应变率增加明显提高.SEM分析发现,TRIP钢断口体现为典型的延性断裂特征,而且残余奥氏体的变形诱发相变对孔洞形成位置的影响使得其具有较好的延性.     

600 MPa级相变诱导塑性钢的动态力学性能

目的研究相变诱导塑性钢不同应变速率下的力学性能,尤其是动态力学性能。方法对600 MPa级相变诱导塑性钢进行了准静态至动态6种不同应变速率下的力学性能测试,并对各试样断口处残余奥氏体含量进行了测试比对。0.001~0.01 s~(-1)准静态测试在ZWICK Z050万能试验机上完成,0.1,1,10,100 s~(-1)动态测试在ZWICK HTM5020液压伺服高速拉伸试验机上完成。结果力学测试结果表明,TRIP600具有明显的应变速率效应。在较高速率下,随应变速率的升高材料屈服强度、抗拉强度及伸长率都有一定程度的提高。结论断口处残余奥氏体含量在较高速率下无明显差别,表明较动态条件下应变速率对残余奥氏体转变影响不明显。     

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...     

HSLA TRIP钢的动态拉伸行为及其模拟

研究了HSLA TRIP钢的相变诱发塑性,并模拟了其动态流变行为．结果表明,HSLA TRIP钢是应变率敏感的,屈服强度和抗拉强度均随着应变率的提高而增大,断裂延伸率降低．其变形机理是应变率硬化、绝热软化和残余奥氏体的应变诱发相变等因素的综合作用．计及拉伸流变过程中准静态向热激活、热激活向粘性拖曳及热激活和粘性拖曳综合作用和高应变率热软化特性,计算结果与实验具有较好的一致性．在高应变率拉伸变形过程中HSLA TRIP钢的塑性功热转化率为0．8-0．9．     

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.