连续柱状晶Cu-ECAP中的晶界演变及其与剪切带的交互作用

金属发生塑性变形时形成的剪切带在高应变状态下会被分割为孪晶-基体片层状组织,而纳米尺度的孪晶界能实现材料强塑性的高度匹配。因此,利用等通道转角挤压(ECAP)技术研究剪切带的形成与作用可为材料的强塑性匹配提供有效支持。通过对具有特殊晶界角度的连续柱状晶纯Cu进行1道次ECAP变形,研究变形过程中晶界的演变,分析变形过程中剪切带的形成机制及与晶界的交互作用,测试了不同晶界角度试样变形后的力学性能。结果表明:ECAP变形后,0°晶界发生弯折,内角处晶界顺时针转动50°,30°晶界顺时针转动5°,45°晶界弯曲并呈现出"汤匙"状,60°晶界中心发生弯曲,90°晶界未发生变形。试样变形过程具有多个受力区域,各区域应力状态不同,多种应力交替作用使变形过程中的应变分布极不均匀,从而导致宏观变形存在较大差异。拉伸实验结果表明,具有0°晶界的晶体抗拉强度最高,达到325 MPa,其次是具有45°晶界的晶体,达到295 MPa,而具有60°晶界的晶体抗拉强度最小,为230 MPa。晶体变形后晶粒内形成大量的剪切带,剪切带与晶界的交互作用使晶界发生弯曲。剪切带与晶粒取向及晶界夹角的不同是造成材料变形后抗拉强度产生较大差异的因素之一。     

大角度ECAP变形模具制备纯钛的变形织构演化模拟

为了研究等径弯曲通道变形(ECAP)对纯钛变形织构的影响,本研究采用135°模具在室温条件下以C方式对纯钛实施2道次ECAP变形,然后利用X射线衍射(XRD)仪检测了原始纯钛以及ECAP变形后纯钛的织构,并与VPSC自洽理论模型计算的ECAP变形织构进行对比分析。结果表明:原始纯钛组织为等轴状,晶界清晰,其{0002}晶面极图的最大极密度为2.6,且主要为P_1织构,易发生柱面滑移,同时压缩孪生系处于易激活状态。而经1道次ECAP变形后的织构转变为P织构,同时出现C_2织构。经过2道次ECAP变形后,P织构消失,只存在C_2织构。VPSC自洽理论模型计算织构与实验织构大致相同,且2道次ECAP变形之后的纯钛试样均易发生基面滑移、拉伸孪生系更易被激活。     

等径弯曲通道变形织构的研究进展

综述了等径弯曲通道变形制备FCC、BCC、HCP金属材料中织构的研究进展。介绍了ECAP变形织构的主要研究方法——蚀坑法、X射线衍射法、中子多晶体衍射法和电子背散射衍射法,论述了挤压路径、挤压道次、挤压温度、模具夹角、形变孪晶、初始织构等对ECAP变形过程织构演变及形成机理的影响,并对基于物理过程的织构演化模型(全约束Taylor多晶体模型和粘塑性自洽多晶体模型)进行评价,同时进一步指出织构演化研究的重要性及发展趋势。     

ECAP变形与材料组织性能控制的研究

等径弯曲通道变形(ECAP)是制备超细晶材料的新工艺,其基本原理是将试样放入横截面形状完全相同、并成一定角度的弯曲通道中,试样在压力作用下通过通道时,在通道弯曲处产生一定量均匀的纯剪切变形,最终获得很高的变形量,使材料组织发生明显细化.详细介绍了ECAP变形工艺路线对晶粒细化的影响,以及ECAP变形制备超细晶材料的显微组织特征及其力学性能.     

ECAPT 过程中 TE 工艺对 ECAP 变形规律的影响

通过对纯铝等径角挤压(ECAP)和等径角挤扭(ECAPT)变形行为的数值模拟,获得了材料在不同工艺下的应变和损伤情况.结果表明,在ECAPT工艺中试样通过ECAP通道后能获得比单独的ECAP更高的应变累积,应变累积量随TE通道螺旋角β的增大而增大,同时试样内部的应变分布也得到改善,试样在受到TE工艺的背压后材料表面受到剪切破坏的可能性也明显降低.     

室温90°模具ECAP变形工业纯钛的力学性能

采用两通道夹角Φ=90°,外圆角Ψ=20°的模具,在室温,以C方式(两次挤压道次之间试样绕纵轴旋转180°)对工业纯钛进行了4道次ECAP(Equal Channel Angular Pressing)变形,成功制得表面光滑无裂纹试样,并对其力学性能和微观组织进行了检测分析.结果表明,工业纯钛经室温4道次ECAP变形后,原始晶粒细化到170 nm左右,显微维氏硬度和抗拉强度分别由1 792 MPa、438 MPa提高到2 486 MPa、728 MPa,且保持良好的塑性,断后伸长率为21.4%.     

基于电子背散射衍射分析晶粒大小分布和微观织构的关系

采用电子背散射衍射技术检测了三种薄钢板试样的晶粒尺寸统计分布规律,并测定了取向成像图和取向分布函数图,统计了各织构晶粒所占比率以及晶粒取向差分布状况。分析了晶粒大小统计分布状况对微观织构形成的影响。结果表明:晶粒尺寸分布越集中,越利于增加{111}∥ND有利织构的含量;取向成像图和取向分布函数图所分析的织构结果是一致的,晶粒取向差分布状况与织构特征的形成有一定的对应关系。     

封面图片说明

正封面图片出自论文"超细晶纯铝微塑性变形本构关系的建立".超细晶材料具有优异的室温机械性能和高温延展性,能够有效降低晶粒尺度效应,在微成形技术中具有潜在应用.利用等通道挤压工艺制备了超细晶纯铝材料,该幅图片为经过150℃退火处理后EBSD晶粒取向图,平均晶粒尺寸为1.5μm.研究了超细晶纯铝微压缩变形行为,分析了试样尺寸、变形温度以及应变速率对超细     

挤压速度对工业纯钛室温ECAP变形孪晶的影响

在室温采用通道夹角为Φ=120°的模具,以不同挤压速度实现工业纯钛的单道次等径弯曲通道变形(ECAP),利用光学显微镜(OM)观察了变形前后的组织形貌特征,分析了不同挤压速度对显微组织的影响。结果表明:在单道次ECAP变形过程中,孪晶变形是主要的变形机制,且随着变形速率(即挤压速度)的增大,孪晶变细,孪晶的密度显著增大。     

室温ECAP和冷轧复合变形工业纯钛的组织和性能

采用ECAP技术和常规冷轧复合变形工艺制备了高强度工业纯钛,研究了复合变形后试样的力学性能与显微组织的关系.结果表明,工业纯钛经室温单道次ECAP和冷轧复合变形后,晶粒被严重拉长,形成了明显的纤维状组织,试样的抗拉强度高达805MPa;随着冷轧变形量的增大,变形组织的细化程度和均匀性提高,使试样的强度和塑性进一步提高.位错滑移和孪生是工业纯钛室温ECAP和冷轧复合变形的主要变形机制.     

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.     

Effect of Permeable Crystalline Material on Steel Reinforcement Corrosion of Concrete

Permeable crystalline materialcan permeate into pores and cracks of concrete and catalyze the reaction between Ca(OH) 2and unhydrated cement to generate a great quantity needle non-soluble crystals, which can stop up the pores and cracks of concrete, and increase the impermeability of concrete. This paper reported the results of a study conducted to evaluate steel reinforcement corrosion of concrete specimens uncoated and coated with permeable crystalline material as well as mixed with the permeable crystalline material. The properties evaluated for corrosion test were water impermeability, water absorption, compressive strength and potential. The results of water impermeability, water absorption, compressive strength clearly showed that the permeable crystalline material could prohibit water, any soluble salts and moisture from penetrating the concrete to cause corrosion, leaking, and other problems, and it did increase the compressive strength, which was favorable for protection of corrosion of reinforcing steel. Moreover, it was concluded from the potential-time curve that the steel reinforcement of uncoated specimen was in the state of activation whereas that of other specimens coated and mixed with the permeable crystalline material was in the state of inactivation. Above all, it was indicated that the permeable crystalline materialis very effective to protect the steel reinforcement of concrete from corrosion.     

The Research and Application About "Dry Peeling Off" Technology for Airplane Surface Paint Layer

In this paper, the principle of spurting take off lacquer were introduced; and with orthogonal method the unsaturate polyester was prepared ;it was easy to peel airplane paint layer off with this material and equipment.     

Quality Study of Honeycomb Core Shaping Without Wax Stabilization

Sandwich panels utilizing honeycomb cores result in lightweight, high-strength units that are very rigid. Indeed, they give honeycomb panels the best strength-to-weight ratio of any construction type available. Conventionally, the wax is poured into the cell of the core to strengthen the structure and prevent the core from being crushed during milling. Much time and labor is required to wax, mill, and clean the cores. In this study, the process of pouring wax into the core was skipped. In other words, the cutter directly milled the core. Experiments showed that the compressive strength of the core produced without wax stabilization was only 3% lower than that of cores produced using the traditional method. In addition, the drum peel strengths of cores produced without wax stabilization were 38.4% higher than cores produced using the traditional method, in which residual wax seriously polluted the adhesive. It was also found that eliminating the wax process can reduce costs.     

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.     

In-process thermal treatment of polylactic acid in fused deposition modelling

Polylactic acid (PLA) is one of the most widely used open source fused filament fabrication materials due to its ease of extrusion, biodegradability, and mechanical strength. The mechanical strength of PLA largely depends on the proper growth of its semi-crystalline structure, which can be severely impaired by a low rate of crystallization, particularly in open source printers. This can be further aggravated by the non-uniform thermal distribution of heat that causes improper curing among the extruded beads of the printing material. As a result, PLA printed on open source printers does not achieve the best mechanical properties. This research, for the first time, proposes an additive-free solution implemented through a detailed set of experimentation to improve the curing rate through in-process temperature variations to cure the joints among the beads. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy is used to confirm the improvements in the bead joints. This work is conducted in two phases of experiments. In the first phase, a full factorial ANOVA is used to investigate various process parameters and the important variables are used in the second phase to print test specimens in four different sets.     

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.     

Early ironwork in Biscay: Survey,excavation, experimentation and materials characterization. An integral study of the mountainside ironworks (ferrerías de monte or “haizeolak”)

ABSTRACT

The production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials.