偏量应变定标模型在Nb_3Sn股线中的应用

采用Pacman弹簧装置测量在不同磁场,温度和应变条件下Nb3Sn多芯股线的V-I特征曲线。外部磁场变化范围由4T到14T,温度变化由4.2K至10K,材料轴向应变变化范围在-0.9%～+0.6%。在此基础上详细介绍了近年来应用广泛的三维偏量应变定标模型,通过该定标模型模拟了Nb3Sn超导材料临界电流Ic随应变状态的变化规律。     

Nb3Sn超导股线热应变分析模型研究

ITER聚变反应堆上Nb3Sn超导股线是由脆性金属间化合物构成的,由于其间各组分不同的热胀冷缩系数和不同的弹性模量,使得股线从热反应温度或热处理温度到室温、以至到低温运行时,会在Nb3Sn复合物中产生热应变。为了研究Nb3Sn的热应变和构建相应的数学模型,进行了加热期间局部应变测量以及室温下的拉力测试。根据Nb3Sn股线不同组分应力/应变曲线所显示的弹塑特性,对它们进行量化分析。测试分析发现,在室温下沿轴向加载到Nb3Sn超导丝的局部应变是压缩应变,高温下是拉应变;另外用数值分析计算方法可以再现依靠温度的轴向热应变。     

高场磁体用RRP Nb3Sn股线的研制

采用Rod Restack Process(RRP)研制了单根线长大于1500m的高场磁体用Nb3Sn股线,股线选用Nb作为扩散阻隔层,分布于各亚组元周围。在热处理时Nb阻隔层不但可以阻止Sn向稳定体Cu区的扩散,防止稳定体的Sn扩散污染,确保股线具有较高的剩余电阻率(RRR),同时,靠近Sn源内侧的Nb参与固态扩散反应生成A15相Nb3Sn,贡献临界电流。在股线的制备过程中,采用Nb-47%Ti(质量分数)芯代替部分Nb芯的方式添加元素Ti,达到了Ti元素添加目的,该方法因为使用了已经商业化的Nb-47%Ti而有效控制了制作成本。对该股线进行热处理以及超导性能测试研究表明:640℃,60h热处理条件下,股线在12T,4.2K,0.1μV/cm下的Ic为514A,股线的RRR为148,具有良好的绝热稳定性;在650℃,100h下股线的Ic为599A,RRR=3.77。股线扩散阻隔层以及添Ti方式的成功选择,为获得长线打下了基础,为股线性能的初步研究及后续的实验提供了直接参考。     

应变对Nb_3Sn股线临界特性退化影响

为应对12 T以上的磁场影响,国际热核聚变反应堆ITER和国内CFETR装置上环向和中心螺线磁体系统已采用Nb3Sn材料;而低温下临界温度和分流温度是超导体稳定运行的重要因素,由于缺乏应变效应对临界温度和分流温度影响的研究,为此,本研究利用模拟应变作用的周期载荷,对Nb3Sn超导股线样品的临界温度和分流温度进行了测试以及数值模拟计算,分析获得扭距等作用使临界温度和分流温度随模拟应变载荷周期退化的结果。同时,推导分流温度随周期载荷变化的双对数分布模型,模型可以描述股线样品中由周期载荷导致的弯曲应变所产生的股线性能降级情况。     

枪管渐速膛线数控电解加工方法的研究

针对现有膛线电解加工方法存在的只能加工固定缠距膛线、不能加工渐速膛线等问题,根据膛线电解加工方法和工作原理,提出枪管渐速膛线数控电解加工方法。通过对渐速膛线数控电解加工方法相关理论的分析,确定渐速膛线数控电解加工方法原理方案。新的渐速膛线数控电解加工方法不仅解决了在同一台设备上加工不同类型和规格膛线的问题,而且简化了机床结构,为枪管膛线电解加工提供了新的加工方法和设备,对枪管膛线的研究和发展具有重要的作用和实用价值。     

采用中子衍射研究内锡法Nb3Sn的相形成

选取2种ITER用内锡法Nb3Sn复合超导线，采用原位中子衍射测量技术检测超导相的形成过程，通过添加第3种元素研究合金化Sn芯和合金化Nb芯对超导相形成过程及超导线超导性能的影响。结果表明：合金化Sn芯比合金化Nb芯丝有利于提高超导性能；少量添加第3种元素Ti与Sn形成合金能显著促进Sn的扩散和A15相的形成，并且能有效抑制Nb3Sn晶粒的生长，因此增加了晶界面积和钉扎力，增强了超导特性，提高了非铜区临界电流密度Jcn。     

螺旋通道长度对纯铝粉末多孔材料等径角挤扭变形的影响

针对等径角挤压和挤扭两种工艺的不足,在充分发挥各自优势的基础上,提出了一种新型的大塑性变形工艺——等径角挤扭(Equal Channel Angular Pressing and Torsion,ECAPT)。采用DEFORM-3D软件对纯铝粉末多孔材料等径角挤扭成形过程进行单道次三维有限元模拟,重点分析螺旋通道长度对变形试样挤压载荷、等效应变、致密行为等场量变化规律的影响。结果表明,相比于传统的ECAP变形,ECAPT工艺螺旋通道的存在,可大大增加变形试样内部的静水压力;合理的螺旋通道长度,可有效提高变形试样的累积应变量和应变分布均匀性,显著改善变形试样的整体致密效果。文章在综合考虑最优数值模拟结果的基础上,自行设计了螺旋通道长度为30mm的ECAPT模具,并进行了相关实验验证,证明了所建立有限元模型的可靠性。     

电阻焊接技术制备Nb3Sn-NbTi 混合超导接头

在强磁场超导磁体应用中,特别是具有高稳定度高场超导磁体,具有极低电阻的超导接头发挥着重要作用。通过电阻焊接方法制备了Nb₃Sn 和NbTi的异种材料超导接头。首先通过烧结法制备了Nb₃Sn的超导接头,然后通过电阻焊接将Nb₃Sn超导接头与NbTi超导体焊接成型。分析了Nb₃Sn超导接头制备过程中Nb₃Sn的微观组织结构和相变。利用无损检测CT对接头结构进行三维重构,分析了Nb₃Sn 和NbTi超导接头内部的缺陷和2种不同材料间的微观连接状态。最后,在背景磁场下对超导接头的电阻性能进行了测试和研究。结果表明,与传统超导焊料制备的超导接头相比,电阻焊接制备的超导接头显示出良好的耐磁场性能,在1.5 T背景磁场下具有较低的电阻值。     

HP45NbTi高温合金炉管的焊接

分析了HP45NoTi高温合金炉管的焊接性,采用NiR82镍基焊丝手工钨极氩弧焊打底、25-35Nb焊丝填充并盖面的焊接工艺,焊接了外径125 mm、壁厚11mm的离心铸造HP45NbTi高温合金炉管对接接头,获得了常温和高温下都满足使用要求的焊接接头,并分析了焊接前后组织的分布情况.     

Microstructure and properties of Nb<Subscript>3</Subscript>Sn superconductors for the magnet system of the international thermonuclear experimental reactor

Results of a study of promising Nb₃Sn superconductors fabricated with the use of a “bronze” method and a method of “internal source of tin” for toroidal coils of the magnet system of the international thermonuclear experimental reactor (ITER) are presented. The main structural parameters and factors of the process of manufacturing technical superconductors based on Nb₃Sn, which determine the superconducting properties, are analyzed. The current-carrying capacity and the losses to hysteresis are determined for conductors with various diameters. The structure of the layer of superconducting Nb₃Sn compound is studied, and the relation between the structural parameters and the superconducting properties of the developed conductors is described. Examples of Nb₃Sn superconductors with a reinforcing element from a nanocomposite alloy Cu - 18% Nb are presented. Strength characteristics of the reinforced conductors are studied. Prospects of further enhancement of superconducting properties of Nb₃Sn superconductors obtained by both methods are estimated.     

通过Nb，Ti扩散反应制备不同成分的超导体

利用Nb片和Ti片交替组配加工,经扩散反应制备了Ti含量在42.56%-56.62%之间的3种不同成分的NbTi超导线。运用扫描电镜(SEM)观察了Nb/Ti界面的扩散形态及微结构,并对热处理工艺和不同Ti含量对临界电流密度(Jc)的影响进行了讨论。结果表明:随着Ti含量增加,可提高超导线在低场(<5T)时的临界电流密度Jc。该工艺制备的NbTi超导线材的Jc可达到2800A/mm2(5T,4.2K)和4200A/mm2(3T,4.2K)。随着Ti含量的增加,试样的Jc在低场时很高,而在高场时的性能偏低,且下降迅速,而Ti含量低的试样的Jc衰减相对缓慢些。对Ti含量较高的合金,在一定温度下,选用较短的热处理时间,可获得高的Jc,对Ti含最较低的合金,则要求较长热处理时间。     

电机轴断裂失效分析

采用化学分析、宏观分析、微观分析和金相检测手段,对电机轴断裂原因进行了探讨.试验结果表明,由于电机轴加工和装配不当,在交变扭转应力作用下,导致花键平齿根部产生应力集中开裂,进而沿轴向断开.最后,在扭转应力作用下促使电机轴发生扭转过载塑性断裂.     

60TY1钢轨UF出钢扭转原因及控制措施研究

针对生产60TY1钢轨时UF轧机出钢扭转问题,采用仿真技术对扭转原因进行了分析,并提出和验证了相应解决措施。根据仿真结果,采用增加轧辊直径、增加轨头压下量和加长出口导卫长度等措施,成功解决了60TY1钢轨UF轧机出钢扭转问题,产品质量达到标准要求。     

Cu与NbTi之间扩散反应的研究

采用电子探针微分析术研究了机械复合和冶金复合两种界面状态的Nb-Ti/Cu复合超导线,以及Nb-Ti/Cu,Ti/Cu和Nb/Cu偶的扩散反应过程.结果表明,原始组件的界面状态对Nb-Ti/Cu间金属间化合物的生成有明显的影响.机械复合组件较冶金复合组件能承受更高的热处理温度而不致生成金属间化合物.Ti与Cu之间反应生成化合物的次序与形态及NbTi与Cu之间不同.Ti/Cu间生成化合物的厚度y与时间t关系遵循y~(1.5-t)的规律.     

DIFFUSION REACTIONS BETWEEN Cu AND NbTi-ALLOY

Diffusion reaction of superconductig composite NbTi/Cu assembled both mechanicallyand metallurgically,diffusion couples Ti/Cu and Nb/Cu have/been studied by means ofEPMA.The results indicate that the initial interface state of thecomposite NbTi/Cu significantly affects the forming process of intermetallic compounds atthe interface.In comparison with the metallurgically bound composite,the intermetallic com-pounds forms at a higher temperature in mechanically bound one.Therefore.the mechanicalhinding process is beneficial to the production of NbTi/Cu superconducting composite.No intermetallic compounds have been observed in Nb/Cu system.The morphology ofintermetallic phases and the sequence in which they form in Ti/Cu system are somewhatdifferent from that in NbTi/Cu.The relationship between the thickness of compound layerand annealing time obeys the rule of y~(1.5) ∝ t.     

Influence of diffusion annealing on residual resistivity of Nb3Sn-based chromium-plated strands obtained by a bronze process

The residual resistivity ratio, R₂₇₃/R₂₀, is an important parameter for multifilament superconductors (strands) based on Nb₃Sn that are used to manufature cables of magnetic systems. High values of RRR impart stability to the cable with regard to thermal excitations. Nb₃Sn strands for magnetic system of the International Thermonuclear Experimental Reactor are manufactured from high purity oxygen-free copper with RRR > 250 units; however, after extended diffusion annealing intended to form superconducting phase Nb₃Sn, the residual resistivity ratio values of the strands decrease. This work investigates the influence of diffusion annealing for 55?C200 h during the final stage at 650°C on the residual resistivity ratio of chromium-plated Nb₃Sn strands. The contents of chromium and oxygen have been analyzed using X-ray spectral microanalysis of the strand surface and peripheral copper layers. Mass spectrometry with inductively coupled plasma (ICP mass spectrometry) has been used to determine the total chromium content in the copper shell. The influence of chromium and oxygen diffusion from coating during annealing at 650°C on the residual resistivity ratio has been demonstrated. Based on the data of ICP mass spectrometry, the depth of the penetration of chromium in a copper shell has been assessed.     

风窗支柱内腹板扭曲与回弹的解决过程

介绍了风窗支柱内腹板在拉深成形修边后存在回弹、扭曲的问题,通过采用过成形法和消除残留应力法对零件进行整改,成功解决了零件的回弹和扭曲,生产的零件满足设计要求。     

加工TiNi形状记忆丝的新工艺

采用模拟试样研究了Ti/TiAl、Nb/TiAl和NbTi/TiAl 3种复合材料的界面特性。结果表明,爆炸试样的界面反应层厚度远小于热等静压试样的界面反应层厚度。在同一条件下热等静压成型的这3种复合材料,其界面差异明显:Ti/TiAl和NbTi/TiAl试样的界面反应层较厚,界面结合强度较高;Nb/TiAl试样的界面反应层较薄,界面结合强度较低。     

Ti5Nb人工钉扎NbTi多芯超导体的磁通钉扎特征

采用棒基组合的装配方法、多次热挤压和冷加工相结合的工艺，制备了2种以Ti5Nb(a-Ti)作为人工钉扎中心(APC)的NbTi超导多芯线。研究了Ti5Nb APC NbTi多芯超导体的磁通钉扎力曲线特征。讨论了人工钉扎中心尺寸的大小dp对磁通钉扎力的影响。分析了Ti5Nb APC与Nb APC NbTi多芯超导体的磁通钉扎力曲线特征不同的原因。结果表明：随着线径的逐渐减小或Ti5Nb尺寸的减小，其钉扎力峰值逐渐增加，并且向更高的磁场移动。与NbAPC相比，Ti5Nb APC NbTi超导多芯线Fpmax峰值出现在更高的磁场下。     

Microstructure and properties of Nb3Sn superconductors for the magnet system of the international thermonuclear experimental reactor

Results of a study of promising Nb₃Sn superconductors fabricated with the use of a bronze method and a method of internal source of tin for toroidal coils of the magnet system of the international thermonuclear experimental reactor (ITER) are presented. The main structural parameters and factors of the process of manufacturing technical superconductors based on Nb₃Sn, which determine the superconducting properties, are analyzed. The current-carrying capacity and the losses to hysteresis are determined for conductors with various diameters. The structure of the layer of superconducting Nb₃Sn compound is studied, and the relation between the structural parameters and the superconducting properties of the developed conductors is described. Examples of Nb₃Sn superconductors with a reinforcing element from a nanocomposite alloy Cu - 18% Nb are presented. Strength characteristics of the reinforced conductors are studied. Prospects of further enhancement of superconducting properties of Nb₃Sn superconductors obtained by both methods are estimated.