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1.
介绍了难熔金属及其合金单晶的制备技术,对电子束悬浮区域熔炼技术和等离子弧熔炼技术进行了比较。电子束悬浮区域熔炼法温度梯度易于控制、材料不受坩埚材料污染,但熔体表面张力对活性杂质和温度梯度敏感性高,所能制备的高纯难熔金属及其单晶材料尺寸规格受到很大限制,且材料内部位错密度较高。等离子弧熔炼法加热源能量密度高,原料规格形式多样,可制备单晶棒材、板材、管材及其他特定形状的单晶铸件,可最大程度地去除杂质元素(尤其是C元素),但设备系统复杂,单晶材料位错密度大。讨论了单晶材料发展现状,通过固溶强化可进一步提高材料的高温性能及其稳定性。单晶管材的制备也是一个发展方向。此外还对单晶材料制备技术和发展前景提出了一些建议。  相似文献   

2.
介绍了难熔金属及其合金单晶的制备技术,对电子束悬浮区域熔炼技术和等离子弧熔炼技术进行了比较。电子束悬浮区域熔炼法温度梯度易于控制、材料不受坩埚材料污染,但熔体表面张力对活性杂质和温度梯度敏感性高,所能制备的高纯难熔金属及其单晶材料尺寸规格受到很大限制,且材料内部位错密度较高。等离子弧熔炼法加热源能量密度高,原料规格形式多样,可制备单晶棒材、板材、管材及其他特定形状的单晶铸件,可最大程度地去除杂质元素(尤其是C元素),但设备系统复杂,单晶材料位错密度大。讨论了单晶材料发展现状,通过固溶强化可进一步提高材料的高温性能及其稳定性。单晶管材的制备也是一个发展方向。此外还对单晶材料制备技术和发展前景提出了一些建议。  相似文献   

3.
主要论述水冷铜坩埚内的Czochralski定向凝固、电子束定向凝固、光悬浮定向凝固、整体定向凝固和电磁冷坩埚定向凝固5种定向凝固的基本原理,优缺点以及研究定向凝固Nb-Si基超高温合金所取得的进展。现阶段,基本不用Czochralski定向凝固和电子束定向凝固研究Nb-Si基超高温合金了;到目前为止,光悬浮定向凝固是制备研究Nb-Si基超高温合金的主要手段;整体定向凝固制备的Nb-Si基超高温合金的断裂韧性已达20MPa·m1/2左右;电磁冷坩埚定向凝固制备的Nb-Si基超高温合金的高温拉伸强度已达200MPa(1250℃)。  相似文献   

4.
难熔元素对镍基单晶高温合金凝固特性及组织的影响   总被引:3,自引:1,他引:2  
镍基单晶高温合金的性能与难熔元素Re、W、Ta等的含量之间有着紧密的联系.总结了在镍基单晶高温合金的发展过程中难熔元素添加的特点,综述了难熔元素对镍基单晶高温合金的凝固特性与凝固组织的影响,并指出了其中存在的问题,展望了未来研究发展的方向.  相似文献   

5.
采用电子束悬浮区熔装置(EBFZM)制备了Si-TaSi2共晶自生复合场发射材料,系统地研究了Si-TaSi+2共晶的定向凝固组织特征.当凝固速率在0.3~9.0mm/min范围内变化时,均可获得Si-TaSi2共晶自生复合材料,具有高精确取向的TaSi2纤维在硅连续基体中均匀分布.随着凝固速率的增大,TaSi2纤维的直径和平均间距减小,面密度和体积分数增大.采用零功率法考察了不同凝固速率时的固-液界面形貌.当凝固速率由0.3mm/min变化到5.0mm/min时,固-液界面经历了平界面→浅胞状界面→胞状界面→平界面的演化过程.  相似文献   

6.
先进定向凝固技术   总被引:10,自引:1,他引:9  
简要回顾了传统定向凝固技术及其存在的问题,概述了西北工业大学凝固技术国家重点实验室近年来在定向凝固技术领域所取得的重要成果,其中包括超高梯度定向凝固,电子束区熔定向凝固,深过冷定向凝固,电磁约束成形定向凝固,单晶连铸,经熔体热处理的定向凝固等先进定向凝固技术。提出了外场作用下定向凝固的新构想。  相似文献   

7.
以电子束真空熔炼直接定向凝固技术制备5N高纯铜大铸锭为研究目标,利用电子束熔炼原材料,熔体直接定向凝固后得到高纯铜铸锭.采用GDMS-VG9000辉光放电质谱仪和TCH600氧氢分析仪研究了金属杂质及氧氢元素的去除效果,通过EPMA-1600电子探针研究了提纯后元素的分布情况.结果表明:真空电子束熔炼直接定向凝固技术可将原料为4N(99.9988711%)的电解阴极铜板,制备出纯度5N(99.9997235%)、Φ59 mm大尺寸高纯铜铸锭,杂质元素总量降低了75.506%,中间凝固组织为单晶;五种含量较高的元素Ag、Cu、O、P和S均匀分布,没有出现杂质的偏聚现象;与原材料相比,0、H元素分别降低了86.47%,85.00%.研究表明真空电子束精炼直接定向凝固技术能够制备氧氢含量较低的5N大尺寸高纯铜铸锭.  相似文献   

8.
定向凝固和单晶高温合金及涡轮叶片的发展   总被引:6,自引:0,他引:6  
北京航空材料研究所对定向凝固及单晶高温合金及工艺进行了多年卓有成效的研究,建立了先进的定向凝固设备,发展了定向凝固工艺,研制了一系列高性能定向和单晶高温合金;对合金设计、热处理、合金元素的作用进行了分析研究,为确定合适的化学成分及选定最佳工艺参数提供了可靠的基础;进行了精密铸造工艺的研究,发展了无余量铸造技术和用于定向及单晶的陶瓷型壳和型芯,并用此发展了多种航空定向和单晶叶片,特别是研制和批生产了用于先进航空发动机的DZ22无余量具有复杂内冷通道的空心涡轮叶片。现在,其主要目标是研制无余量的单晶空心叶片及其他单晶课题。  相似文献   

9.
《真空》2015,(4)
介绍了真空电子束区熔炉技术性能、区熔原理、设备结构及特点。该设备是国内第一台国产化的电子束区熔炉,能够对最大尺寸为φ30mm×1000mm的难熔金属及其合金棒料进行悬浮区域熔炼提纯,而且可以进行难熔金属及其合金单晶的制备工艺。该设备的研制成功,对我国难熔金属区域熔炼提纯及单晶制备技术的研究和生产具有重要的现实意义。  相似文献   

10.
超磁致伸缩合金TbDyFe的晶体生长过程   总被引:1,自引:0,他引:1  
用超高温度梯度真空悬浮区熔定向凝固法制备了TbDyFe超磁致伸缩合金,研究了TbDyFe合金的晶体生长方式、轴向择优取向和磁致伸缩性能.结果表明:用悬浮区熔法可制备出轴向择优取向为<110>方向和<113>方向的TbDyFe合金;在20MPa的预应力和5l7.5kA·m-1的磁场下,取向为<110>和<113>的合金样品的磁致伸缩系数分别为l.8×10-3和1.6×10-3.随着生长速度的增大,TbDyFe合金由小晶面生长方式向非小晶面生长方式转变;使用取向为<110>或<113>的晶粒作籽晶,能加快晶粒的择优竞争生长,有利于<110>方向或<113>方向的轴向择优取向的形成;高温退火能不同程度地提高合金的磁致伸缩性能.  相似文献   

11.
电子束冷床熔炼工艺作为一种新型熔炼技术,可应用于生产航空发动机用优质钛合金及回收残钛。本文综述了电子束冷床熔炼TC4合金研究进展。  相似文献   

12.
During last fifteen years various superior surface characteristics including extremely high corrosion resistance and unique electrocatalytic activity have been found for novel melt-spun ribbon-shaped amorphous alloys. Preparation of those amorphous alloys as surface alloys covering bulk conventional crystalline metals has been eagerly awaited for the purpose of utilizing their superior surface characteristics. This is a review of efforts devoted to developing methods for processing amorphous surface alloys by instantaneous melting of a very restricted volume of the surface by irradiation with a CO2 laser or electron beam and subsequent self quenching by the cold bulk substrates. Processing of a wide area by these high energy density beams requires heating the previously amorphized phase, which is easily crystallized by heating. Consequently, high energy density beam processing is most difficult among various methods for preparation of thermodynamically metastable amorphous alloys. Nevertheless, various amorphous surface alloys have been successfully prepared. The materials consisting of the amorphous surface alloys and bulk crystalline metals are quite suitable for corrosion resistant materials and electrodes for electrolysis of aqueous solutions. A comparison of CO2 laser and electron beam processing showed the superiority of the latter to the former because of a significantly shorter processing time.  相似文献   

13.
The process of obtaining nanoparticles of pure metals by melting down initial powder particles using the infrared emission and by charging them electrically in an electron beam with the subsequent splitting them to nanodrops is investigated numerically. The possibility of a substantial increase in the duration of the drop’s stay in the working zone due to the effect of an electrostatic trap is shown, which allows the requirements for the electron beam to be lowered, the range of initial conditions to be extended, and the stability of the process as a whole to be enhanced by implementing the cascade splitting of drops of all sizes in a single regime.  相似文献   

14.
Solid-state additive manufacturing and repairing by cold spraying: A review   总被引:1,自引:0,他引:1  
High-performance metal additive manufacturing (AM) has been extensively investigated in recent years because of its unique advantages over traditional manufacturing processes. AM has been applied to form complex components of Ti, Fe or Ni alloys. However, for other nonferrous alloys such as Al alloys, Mg alloys and Cu alloys, AM may not be appropriate because of its melting nature during processing by laser, electron beam, and/or arc. Cold spraying (CS) has been widely accepted as a promising solid-state coating technique in last decade for its mass production of high-quality metals and alloys, and/or metal matrix composites coatings. It is now recognized as a useful and powerful tool for AM, but the related research work has just started. This review summarized the literature on the state-of-the-art and problems for CS as an AM and repairing technique.  相似文献   

15.
Innovative electron‐beam welding of high‐melting metals Since its establishment as nuclear research plant Juelich in the year 1956, the research centre Juelich (FZJ) is concerned with the material processing of special metals. Among those are, above all, the high‐melting refractory metals niobium, molybdenum and tungsten. Electron beam welding has always been considered to be an innovative special welding method; in the FZJ, electron beam welding has, moreover, always been adapted to the increasing demands made by research partners and involved manufacturing and design sectors. From the manual equipment technology right up to highly modern multi‐beam technique, the technically feasible for fundamental research has, this way, always been realised.  相似文献   

16.
A Fortran program is described for calculating and plotting time-temperature-crystallization curves during rapid heating and cooling by, for example, laser glazing, electron beam melting, melt-spinning or other techniques for the production of metallic glasses and metastable phases. Experiments were carried out to demonstrate the applicability of the program. In the case of Fe-B alloys produced by melt-spinning the behaviour during continuous cooling and isothermal annealing could be predicted. In the case of Ni-Nb alloys the program was used to establish the experimental conditions for the formation of metallic glass by electron beam melting. The program was also used to determine the conditions necessary for glass formation by laser melting a surface layer of boron alloyed to the surface of an Fe-Cr substrate.  相似文献   

17.
为研究电子束扫描铝硅合金表面的熔化及凝固特征,基于价电子理论计算了合金内各相的价电子结构;利用金相显微镜、扫描电镜、显微硬度计等测试了试样微观组织与机械性能;分析了凝固后硅相形貌尺寸对材料硬度的影响;探讨了硅相中心产生裂纹的原因.研究表明:硅相及共晶体的结构破坏要比铝的结构破坏难;电子束表面熔凝处理后,试样分为熔化区、过渡区和基体三个区域;且经电子束扫描处理后,硅相得到了明显细化;熔化区内硅相的形貌尺寸小于8.5μm,该区的最高硬度是基体硬度的1.39倍;溶解后硅相周围的密度差是硅相中心产生裂纹的原因.  相似文献   

18.
为了更深入地探究电子束焊接过程中的机理问题,利用数值软件Fluent,对10mm厚的2219铝合金电子束焊接熔池进行三维瞬态模拟。分析电子束焊接进入准稳态后熔池中涡流的变化规律和产生原因,并结合电子束与匙孔壁面相互作用进行讨论。结果表明:电子束焊接进入准稳态后熔池呈周期性波动;根据液态金属流动情况可将焊接熔池分为3个区域,区域Ⅰ中的液态金属维持了熔池体积的稳定,区域Ⅱ中的涡流起到扩大熔池表面的作用,区域Ⅲ中的涡流促使匙孔坍塌;通过对电子束与匙孔壁面的耦合分析可知,电子束在匙孔壁面上并不是均匀分布的,这造成了匙孔底部具有一定的滞后性。  相似文献   

19.
Lotus‐type porous metals whose long cylindrical pores are aligned in one direction were fabricated by unidirectional solidification in a pressurized gas atmosphere. The pores are formed as a result of precipitation of supersaturated gas when liquid metal is solidified. The lotus‐type porous metals with homogeneous size and porosity of the evolved pores produced by a mould casting technique are limited to the metals with high thermal conductivity. On the other hand, the pores with inhomogeneous pore size and porosity are evolved for metals and alloys with low thermal conductivity such as stainless steel. In order to obtain uniform pore size and porosity, a new “continuous zone melting technique” was developed to fabricate long rod‐ and plate‐shape porous metals and alloys even with low thermal conductivity. Mechanical properties of tensile and compressive strength of lotus‐type porous metals and alloys are described together with internal friction, elasticity, thermal conductivity and sound absorption characteristics. All the physical properties exhibit significant anisotropy. Lotus‐type porous iron fabricated using a pressurized nitrogen gas instead of hydrogen exhibits superior strength.  相似文献   

20.
Microstructure Characteristic of Ni-Nb near eutectic alloy is systematically investigated during directional solidification with electron beam floating zone melting (EBFZM). The effect of the Zone melting rate on the microstructure has also been studied.  相似文献   

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