铋系高温超导带材的先进成形技术

铋系(Bi,Pb)2Sr2Ca2Cu3Ox(Bi-2223/Ag)高温超导带材的传统制备工艺难以实现其性能提升。为了改善带材综合性能,从超导带材成形过程中的缺陷及问题出发,介绍了高强度金属外包套材料、多芯线材跑道模拉拔和热等静压三种先进技术。提出了可应用于实际工程的方案,以提高铋系高温超导带材的力学性能。     

轧制及退火工艺对C5071青铜带材组织与性能的影响

C5071青铜带材制备过程中,轧制工序不同道次加工率及中间去应力退火工艺对带材的组织与力学性能具有重要影响。结果表明,选取较小的加工率86.21%开坯粗轧至2.0 mm时,带材表面平整,无边裂缺陷及明显组织缺陷;中轧工序加工率为66.0%时,带材抗拉强度、延伸率及硬度合适,板型较平直。最优轧制工艺制备的0.5 mm成品分别在210、230和290℃温度下保温3.5 h进行低温退火处理,随着退火温度升高,成品抗拉强度由526 MPa降至500 MPa,延伸率由13.4%提高至17.2%。退火温度低,带材抗拉强度偏高;退火温度高,带材力学性能偏低,230℃×3.5 h退火后产品综合性能均位于技术要求中间范围。     

Bi-Sr-Ca-Cu-O高温超导材料的连接技术

Bi-Sr-Ca-Cu-O（BSCCO）高温超导材料在电力工程中拥有广阔的应用前景。本文全面概述了国内外研究Bi系高温超导材料连接技术的现状和不足,重点介绍了BSCCO带材常规冷压成形后再高温反应退火的扩散焊连接技术,另外,阐述了近几年采用高温加压直接扩散连接的最新研究成果。     

冷轧工艺对Al—Mg—Li合金力学性能的影响

本文研究了冷轧工艺对０１４２０合金力学性能的影响，结果表明，合金经过退火及包铝处理后，冷轧性能得到改善，合金具有较好的综合力学性能，文中还分析了冷轧工艺对合金强度及塑性的影响，最后得出冷轧变形率与合金力学性能达到最佳匹配的冷轧工艺。     

Bi（2223）／Ag带材均匀性连续检测

对超导Bi（2223）／Ag带来说，由于包套银和Bi（2223）超导陶瓷粉末间机械性能的明显区别，及加工变形工具中应力应变的不均匀分布，使得复合体的应变过程变得十分复杂，个别芯丝的变形变得不均匀，再加上2223相的片状晶特征和陶瓷芯丝在纽构方面和密度上的区别，使Bi（2223）／Ag带中的传输电流呈不规则分布，最终带子沿长度方向局部临界电流密度地会有差别，影响起导带整体的应用性能．为了改善这种不均匀性，提高其带材性能，人们采用各种手段研究带材的不均匀性，最近斯洛伐克的研究者介绍了他们采用四引线法结合合尔探头陈列组成的可…     

平整机延伸率、轧制力及张力的协调控制技术

在引入板形与力学性能综合控制目标函数的基础上，将带材的力学性能与外形质量糅合成一个统一目标进行控制；建立了一套平整机延伸率、轧制力及前后张力协调控制数学模型。通过轧制力与前后张力的协调设定，使平整机既能保证延伸率精度叉可满足板形要求，将其在某厂2030mm连续退火平整机上应用，取得良好效果。     

退火温度对新型锆合金薄板带材析出相和织构的影响

采用扫描电镜和超高分辨透射电镜,对具有良好冲制性能的新型锆合金薄板成品带材进行含晶粒、第二相粒子等在内的显微组织研究,并探索真空退火处理条件下温度对带材显微组织的影响。结果显示:新型锆合金薄板成品带材晶粒平均尺寸2.17 μm,存在{0001}<1010>和{0001}<1120>两种织构,大部分晶粒<1120>平行带材RD方向,较少晶粒<1010>平行带材RD方向;第二相粒子分布在晶粒内部及晶界,平均尺寸114 nm,尺寸较大的为不规则椭圆形的Zr-Nb-Fe相,尺寸较小的为圆形的β-Nb相;热处理退火温度降低,带材晶粒尺寸减小,第二相粒子细小弥散分布;新型锆合金薄板成品带材良好冲制性能主要源于轧制积累应变诱发再结晶过程进行充分,导致晶粒细小及孪晶发生破碎;相对轧制变形,退火对带材冲制性能影响不显著。     

Bi-2223／Ag高温超导带材的有阻连接研究

采用低熔点63%Sn-34%Pb-1%Bi-2%Ag合金钎料膏软钎焊和不去除Ag合金包套的直接扩散连接两种方法进行Bi系超导带材的有阻连接.研究了搭接长度、钎焊保温时间、扩散连接温度对接头显微结构、临界电流和电阻的影响.工艺适当时,两种接头的电阻均能达到10-8 Ω量级且临界电流较高.     

专利信息

(Ⅰ)专利名称:一种铋系高温超导线/带材及其制备方法专利申请号:200410080448.5公开号:CN1588566申请日:2004-10-10公开日:2005-03-02申请人:西北有色金属研究院涉及一种高温超导铋系Bi-2223线材或带材的制备方法。包括成分为Bi-2223超导粉的芯材和包覆在Bi-2223超导体的芯材上的银隔离层。其特征在于在芯材芯部夹有AgMgNi合金丝/带,在丝/带间夹有银隔离层。本发明采用内置合金芯丝的方法,在带材的芯部位置引入合金丝。为防止合金元素与超导芯反应,在合金丝与超导粉之间添加纯银隔离层,使材料的屈服强度与未内置合金丝的普通带材相比由5…     

含铅化合物在BSCCO粉末热处理中的形成与氧释放及吸收关系

为了提高(Bi，Pb)-2223／银超导带材的传输性能，其制备工艺近几年有很大的改进。目前采用PIT法，制备的150m长的(Si，Pb)-2223／银超导带材，在77K和自场下，工程电流密度Jc达到了18kA／cm^2。Bi-2223带材的质量，主要依赖于前驱粉末、机械变形、退火气氛、温度、时间及精确的升温和降温速率等工艺参数。关键是要控制(Bi，Pb)-2223相的形成。     

New Correlations Between Monotonic and Cyclic Properties of Metallic Materials

Knowledge of the cyclic properties of metallic materials is often critical to correctly design structural components. However, cyclic data are not easily available in the literature, while tensile test data are easier to find in specialized sites or vendor catalogs. In this study, the cyclic strength coefficient and the cyclic strain hardening exponent of the Ramberg–Osgood law were evaluated using exclusively data obtained through monotonic tensile tests. The analyses were carried out on a large set of materials. The database used is composed of 338 alloys, mainly iron alloys, but also titanium and aluminum alloys. New subdivisions of the materials were introduced. Several original relations were suggested to correlate static and cyclic strength parameters. The evaluated values of both cyclic strength coefficient and cyclic strain hardening exponent were compared with experimental values coming from cyclic test, obtaining a satisfactory agreement and a higher accuracy if compared with similar relations found in the literature.     

Tensile properties of some copper- and zinc-based alloys: Effects of strain rate and test temperature

This study analyzes the effects of test temperature and strain rate on the tensile properties of some copper-and zinc-based alloys. The copper-based alloys comprised a leaded-tin and an aluminum bronze, whereas the zinc-based alloys were added with various quantities of aluminum. The aluminum bronze attained maximum room-temperature tensile strength, whereas that of the leaded-tin bronze was the least. Among the zinc-based alloys, the one comprising 27.5 mass% aluminum exhibited superior tensile strength, followed by those alloyed with 11.5, 37.5, and 47.5 mass% aluminum in a descending order. Increasing strain rate tended to improve the tensile strength of the alloys. Tensile strength was reduced with an increase in test temperature irrespective of the alloy composition. The aluminum bronze possessed maximum strength regardless of temperature. The leaded-tin bronze attained least strength property at low temperatures, whereas higher test temperatures led to superior strength than the zinc-based alloys. The temperature sensitivity of the strength of the zinc-based alloys decreased with their aluminum content. Tensile elongation of the alloys tended to increase with an increase in strain rate and test temperature. Leaded-tin bronze was least affected in either case. The alloy also attained least elongation irrespective of test conditions. The aluminum bronze showed maximum elongation, at least at high strain rates. In the case of the zinc-based alloys, intermediate range of aluminum concentration led to better elongation. The elongation property of the alloys was affected by temperature in different manners. In a few cases, the elongation initially increased followed by a reduction beyond a specific test temperature, whereas, in other cases, a continuous increase with temperature was noted. The observations made have been discussed in terms of the nature of different microconstituents of the alloys whose effectiveness changes with test conditions. The response of the samples has been further substantiated with their fractographic features and subsurface characteristics.     

珠光体钢丝冷拉拔过程中微观组织及铁素体微区取向与织构演变

采用电子通道衬度(ECC)和电子背散射衍射(EBSD)技术研究了珠光体钢丝冷拉拔过程中微观组织的变化、铁素体微区取向与织构演变,结果表明,珠光体变形组织中存在剪切带(S带),它们的出现与渗碳体片条和拉拔方向之间的夹角有关:夹角越大,S带越多,随着拉拔应变量的增大,纵截面上珠光体片条逐渐转向拉拔方向,S带方向与拉拔方向的夹角逐渐减小,珠光体内的S带会引起铁素体晶粒局部微区取向急剧变化,从而使原有的珠光体团分裂成若干个由铁素体大角度晶界相隔的区域,钢丝拉拔过程中形成平行于拉拔方向的铁素体〈110〉丝织构,随着应变量的增大,平行于拉拔方向的铁素体〈110〉丝织构增强,其它丝织构组分减弱;靠近钢丝中心区域内的〈110〉丝织构增强幅度大于其它区域。     

COMPUTER NUMERICAL SIMULATION OF MECHANICAL PROPERTIES OF TUNGSTEN HEAVY ALLOYS

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Friction Stir Processed AA5182-O and AA6111-T4 Aluminum Alloys. Part 2: Tensile Properties and Strain Field Evolution

In this second part, a state-of-the-art digital image correlation (DIC) technique was used to compute true stress-true strain curves beyond diffuse necking for friction stir processed AA5182-O and AA6111-T4 aluminum alloys. Of particular interest were differences in key tensile properties, such as initial yield point, and ultimate tensile strength, between the base and friction stir processed materials. Tensile coupons cut from the same material used to investigate crystallographic texture via the electron backscatter diffraction technique in Part 1, were strained to failure in a miniature tensile stage. The evolution of two-dimensional strain fields in both the base and friction stir processed materials was explored with incremental and cumulative strain maps computed from digital grids superimposed on each image after testing was completed. The impact of friction stir processing on strain localization just prior to fracture was revealed through changes in incremental strain map contour profiles. It is suggested that grain size refinement due to friction stir processing has a prominent effect on strength, while texture plays a secondary role. This article was presented at Materials Science & Technology 2006, Innovations in Metal Forming symposium held in Cincinnati, OH, October 15-19, 2006.     

Effect of Scandium Additions on the Tensile Properties of Cast Al-6Mg alloys

Effect of aging on the mechanical properties of Al-6Mg alloy doped with varying concentration of scandium ranging from 0.2 to 0.6 wt.% is analyzed. As-cast samples were aged isochronally for 60 min at different temperatures ranging from 100 to 500 °C. Evaluation of mechanical properties of the aged Al-6Mg (Sc) alloys was done by employing an Instron testing machine. Various strain rate of testing were used to find out the values of strain-rate sensitivity of the experimental alloys. The influence of scandium is much pronounced on yield strength than on the tensile strength. Alloys with higher scandium content have shown higher yield strength and the values of strain-rate sensitivity ‘m’ at peak-aged condition have been found to be comparatively high at higher scandium concentration. The fracture of the experimental alloys occurs through microvoid coalescence.     

Microstructures and mechanical properties of the extruded Mg-4Y-2Gd-xZn-0.4Zr alloys

Microstructures and mechanical properties of the Mg-4Y-2Gd-0.4Zr alloy with Zn additions have been investigated. The investigation suggests that the mechanical properties of the alloys have been greatly improved after hot extrusion due to the refinement of microstructures, especially the elongations. The extruded Mg-4Y-2Gd-1.0Zn-0.4Zr alloy displays excellent tensile properties. The ultimate tensile strength and the yield tensile strength are 291 and 228 MPa, respectively, with an elongation of 28%. The additions of Zn have an obvious effect on refining microstructure of the extruded alloys, and the vicker hardness increases with increasing Zn additions. The age hardening responses of the extruded alloys have been investigated at 220 °C. These alloys display unobvious ageing hardness responses.     

合金成分与热处理对6xxx系铝合金力学性能的影响

研究合金成分（Mg,Si,Cu）和热处理（自然时效和预时效）对6xxx系铝合金力学性能的影响。结果表明：合金成分与热处理不仅影响材料的成形性能,而且影响材料的烘烤硬化性能;提高合金中Si含量或Si／Mg比或添加0．3％Cu,可显著提高材料的韧性和成形性能,而预时效将减低材料的韧性和成形性能。对所研究合金的强度、韧性、加工硬化、应变敏感性、成形极限和烘烤硬化性进行了比较和总结。     

AZ31镁合金型材挤压工艺和组织性能分析

对AZ31镁合金T型材挤压成形进行了工艺试验研究，确定了T型材模具各工作带尺寸及限流措施。分析了T型材各部位的力学性能。结果表明，在挤压比较大部位，屈服强度和抗拉强度最高分别为117MPa和254MPa，伸长率为16％。晶粒细小和织构强度提高是屈服强度和抗拉强度增大的原因。高质量型材必须采用流线型模挤压。     

热处理制度对6013和6061合金拉伸性能的影响

研究了自然时效（T4）、人工时效（T6）及室温停放对6013和6061合金常温拉伸性能的影响。结果表明：6013合金具有快速时效特性;经热处理后,6013合金的拉伸强度高于6061合金的且两者延伸率均大于10%。研究还表明：6013和6061合金常温拉伸性能的纵、横向差别很小,说明该合金拉伸性能各向异性不明显。文中还就不同热处理制度影响两种合金拉伸性能的原因进行了分析。