锰元素对TWIP钢层错能和变形机制的影响

根据层错能的热力学模型,计算了Fe-XMn-3Si-3Al 系高强度高塑性TWIP钢的层错能.计算结果表明,随锰含量增加Fe-XMn-3Si-3Al系 TWIP钢层错能增加,在此基础上讨论了锰含量对Fe-XMn-3Si-3Al 系TWIP钢变形机制、力学性能和微观组织的影响.在合金中Mn含量的提高使层错能增加,而层错能的增加使Fe-XMn-3Si-3Al系钢表现出不同的变形机制,即逐渐由TRIP效应变为TWIP效应;同时随着Mn含量的提高,合金的抗拉强度降低,而塑性提高.     

Ni-Al-Re/Ru合金的层错能

使用置换原子计算层错能的热力学模型计算了Ni-Al-Re(Ru)合金的层错能,研究了合金元素和温度对层错能的影响.结果表明:随着温度的提高,Ni-Al-Re(Ru)合金的层错能增加.Ni-6?-4%Re合金的层错能随着温度的提高线性增加.Ni-6%Al-4%Ru合金的层错能,在温度低于500℃时随着温度的提高呈抛物线规律增加,高于500℃时随着温度的提高呈线性规律增加.Al原子可明显降低Ni-6%Al-4%Re(Ru)合金的层错能.随着Al含量的提高,原子偏聚自由能(ΔGγ→εs)降低,使Al原子自发偏聚,并促进γ'有序相的形成和数量的增加,是合金层错能降低的主要原因.而Ru原子降低合金的偏聚自由能,可提高γ'有序相的稳定性.随着温度的升高,原子偏聚引起的自由能(ΔGγ→εs)增加可抑制原子偏聚;当温度高于500℃时,含Ru合金有比Ni-Al-Re合金高的原子偏聚自由能(ΔGγ→εs),故元素Ru能抑制原子的偏聚和TCP相的析出.     

层错能对Fe-Mn-C系TRIP/TWIP钢变形机制影响

对三种不同层错能(SFE)Fe-Mn-C系TWIP钢的变形机制进行了研究.结果表明:在淬火态下,TWIP钢组织为全奥氏体,奥氏体晶粒内存在少量退火孪晶.TWIP钢的层错能随着C、Mn含量的增加而增加.层错能为7 mJ/m2时,变形后出现大量ε马氏体,且随着应变量的增大,ε马氏体峰增强,表现为单一的TRIP效应;层错能为12 mJ/m2时,应变诱导γ→ε→α或γ→α的转变及形成少量形变孪晶,表现为TRIP/TWIP效应;层错能为18 mJ/m2时,变形后形成大量形变孪晶,表现为单一的TWIP效应,抗拉强度和延伸率分别达到851 MPa及49%.随着层错能增加,TWIP钢的断裂机制由沿晶断裂转变为以韧窝为主的塑性断裂.     

形变温度对Fe-20Mn-3Cu-1.3C TWIP钢拉伸变形行为的影响EI北大核心CSCD

运用温控拉伸实验,分析了在-100~200℃范围内变形时形变温度对Fe-20Mn-3Cu-1.3C钢力学性能和形变机理的影响。观察分析了拉伸试样的显微组织,并利用热力学经典模型,估算了温度对孪晶诱发塑性(TWIP)钢层错能的影响。结果表明:随着形变温度的升高,TWIP钢的层错能显著增加,基体中形变孪晶的体积分数逐渐减少,抗拉强度和屈服强度呈下降趋势,而伸长率先升高后降低,塑性变形机制也由孪生为主逐渐转变为以滑移为主。层错能的拟合公式为γSFE=26.73+9.38×10^(-2) T+4.22×10^(-4 )T2-4.47×10^(-7) T^3,与滑移相比,孪生可获得更高的应变硬化率,从而使TWIP钢获得高强度和高塑性。     

Fe-Mn-Al-C系低密度钢及其强韧化机制研究进展

汽车行业的迅速发展使得能源消耗、环境污染等问题日益严重，而开发高强度且轻量化的汽车用钢对节能减排具有重要意义。目前正在研发的第三代先进高强钢包括轻质（Lightweight）钢、Q&P(Quenching and partitioning)钢和中锰钢（Mn质量分数为5%～10%）。其中，Fe-Mn-Al-C系低密度高强钢由于Al元素的加入，在密度降低的同时保持着良好的力学性能，满足第三代汽车用钢对轻量化的要求。同时，由于大量Al、Mn和C元素的添加，Fe-Mn-Al-C系低密度钢的冶炼连铸、微观结构、变形机制、加工过程及应用性能与传统钢种大不相同。本文系统阐述了Fe-Mn-Al-C系低密度钢的成分设计及其中合金元素的作用，介绍了低密度钢的微观组织结构特征；重点讨论了单一铁素体钢、奥氏体基钢、奥氏体基双相钢和铁素体基双相钢的各种强韧化机制，包括固溶强化、细晶强化、沉淀强化及其独特的应变硬化机制，如相变诱导塑性（TRIP）、孪晶诱导塑性（TWIP）、微带诱导塑性（MBIP）、剪切带诱导塑性（SIP）和动态滑移带细化（DSBR）等；并就层错能（SFE）对奥氏体钢变形机制产生的影响进行...     

热力学在材料工程中的应用

示例简介热力学在材料工程中的应用。应用相图热力学计算了 Fe—C—N 相图580℃的等温截面,作为 C、N 共渗处理的参考;和计算了钢中α/γ平衡相界,供双相钢及临界区热处理工艺制订的依据。以热力学方法计算 Fe——C、Fe—X、Fe—X—C(Fe—Ni—C、Fe—一Cr—C、Fe—Mn—C 及 Fe—高 Ni—C)和多元低合金钢,包括渗 C、N 后渗层的 Ms.建立磷在奥氏体晶界偏聚的模型。分析了回火马氏体脆性的机制。以热力学判定贝氏体相变的机制。对材料的裂纹扩展和晶界断裂作了热力学讨论。     

9Ni钢组织演变、合金元素配分及增韧机理的研究

为了研究9Ni钢热处理过程中的组织演变和合金元素配分对强韧化的影响,采用QT(Quenching+Tempering)和QLT(Quenching+Lamellarizing+Tempering)工艺对9Ni钢进行了热处理,并详细分析了热处理过程中组织和成分配分的变化规律.结果表明:奥氏体化淬火后存在极少量的残余奥氏体(γR),主要富C和Si.580℃回火1 h时,QT工艺条件下原奥氏体晶界上逆转奥氏体(γ’)能富C、Si、Mn和Ni元素,晶内的γ’中无明显Ni和Mn富集;QLT处理后,合金元素发生了配分,所有富合金元素相中均富集C、Si、Mn和Ni元素.两相区保温后实现增韧归因于:板条马氏体基体的大角度晶界比例增加、晶粒细化;组织结构得到优化;增加了γ’形核点,使得γ’量增加,导致马氏体基体净化程度进一步提高.     

新型汽车用钢——低密度高强韧钢的研究进展

轻量化已经成为汽车用钢的发展方向,近年来对低密度高强韧钢的开发顺应了这一趋势。Al元素的添加,降低钢的密度,同时提高层错能,影响变形机制。从成分设计与制备、变形机制、组织性能及工业化应用等方面,总结Fe-Mn-Al系、Fe-Al系和中锰系低密度高强韧钢的研究成果,并阐述了低密度高强韧汽车用钢的发展趋势。     

低密度钢中有序析出相的研究进展

随着"减重、节能、降低碳排放"的绿色制造理念越来越深入人心,对传统钢铁材料升级换代的需求显得尤为迫切,第三代汽车用钢已成为各国研发机构和企业关注的焦点。高强度、高韧性、轻量化的先进钢铁材料成为第三代汽车用钢的一个新的研发方向。主要通过在Fe中添加较多的轻质元素如Al、Mn、Si等进行合金成分设计来显著降低钢材密度;同时通过调控基体组织和析出相构成、形态来平衡钢材的强度和塑韧性,从而使钢具有高的强塑积和低的密度。本文针对Fe-Al、Fe-Mn-Al、Fe-Mn-Al-C系低密度钢的成分及组织特征,介绍了低密度钢中Kappa碳化物,(Fe,Mn) Al、Ni Al型B2相,(Fe,Mn)_3Al型DO_3相和β-Mn相的晶格参数及相关性能特征。结合国内外对低密度钢的最新研究,着重对低密度钢相图的热/动力学计算、各有序析出相的元素配分和析出行为(特征、形态、大小)、析出相对钢组织演变与强韧性机制的影响等进行了总结,并基于现有的研究,展望了高强度、高韧性、低密度钢进一步的研究方向。     

合金元素对Fe-Mn-C系TWIP钢力学行为的影响

采用热力学计算、静态拉伸、XRD、OM与SEM等方法分析了Fe-Mn-C系TWIP钢中合金元素对基体力学行为的影响.结果表明:TWIP钢中Mn含量增加时,基体的屈服强度和抗拉强度均减小,总伸长率增大;C含量增加时,其屈服强度和抗拉强度先增大后减小,在0.6％(质量分数,下同)时存在最大值;当Mn含量为20％时,TWIP钢总伸长率随C含量增加而增大,而Mn含量为22％时则相反.TWIP钢的强塑积随Mn含量的增加而增大,其在C含量为0.4％试样中的体现尤为明显.对于Mn含量为20％的TWIP钢,其强塑积随C含量增加而增大;而对于Mn含量为22％的TWIP钢,其强塑积随C含量增加而减小.     

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.     

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.     

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.     

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.……     

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.     

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.