The process of bubble formation in the hot isostatic pressing treated,doped molybdenum wire

Entrapped materials in the bubbles formed in the K- and Si-doped and hot isostatically pressed molybdenum wire were examined by means of scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy. Solidified particles entrapped in the bubbles were identified as Al-K-Si leucite-type oxide. After reheating these solidified particles at 1900 °C for 5 minutes under atmospheric pressure, however, a portion of the particle was homogeneously volatilized. The remainder was identified as an Al-K-Si mullite-type oxide. Therefore, it can be concluded that the added dopants form a single phase upon annealing, and the formation of bubbles in the doped molybdenum wire is due to volatilization of Al-K-Si oxides, not pure elements constituting the oxides.     

轧制钼杆生产磁控管用钼丝质量问题浅析

论述了以直径7.4 mm轧制钼杆为原料,通过合理选择模具公差,提高拉丝温度,增加在线退火,调整石墨乳比重,在直径2.0 mm进行退火,改进拉丝设备,使磁控管用钼丝的直径公差一致均匀,解决了钼丝的劈裂,最大程度减少钼丝的头、尾劈裂,显著提高了钼丝表面质量和物理性能。     

Recrystallization and grain growth of cold-drawn gold bonding wire

Recrystallization and grain growth of gold bonding wire have been investigated with electron back-scatter diffraction (EBSD). The bonding wires were wire-drawn to an equivalent strain greater than 11.4 with final diameter between 25 and 30 μm. Annealing treatments were carried out in a salt bath at 300 °C, and 400 °C for 1, 10, 60 minutes, and 1 day. The textures of the drawn gold wires contain major 〈111〉, minor 〈100〉, and small fractions of complex fiber components. The 〈100〉 oriented regions are located in the center and surface of the wire, and the complex fiber components are located near the surface. The 〈111〉 oriented regions occur throughout the wire. Maps of the local Taylor factor can be used to distinguish the 〈111〉 and 〈100〉 regions. The 〈111〉 oriented grains have large Taylor factors and might be expected to have higher stored energy as a result of plastic deformation compared to the 〈100〉 regions. Both 〈111〉 and 〈100〉 grains grow during annealing. In particular, 〈100〉 grains in the surface and the center part grow into the 〈111〉 regions at 300 °C and 400 °C. Large misorientations (angles >40 deg) are present between the 〈111〉 and 〈100〉 regions, which means that the boundaries between them are likely to have high mobility. Grain average misorientation (GAM) is greater in the 〈111〉 than in the 〈100〉 regions. It appears that the stored energy, as indicated by geometrically necessary dislocation content in the subgrain structure, is larger in the 〈111〉 than in the 〈100〉 regions.     

Recrystallization of W-1 wt pct ThO2 wire

The recrystallization behavior of W-l wt pct ThO₂ wires of two sizes, 0.457 and 0.178 mm (18 and 7 mil), was studied using optical microscopy, transmission electron microscopy, hardness, and resistivity ratio techniques. For the 0.178 mm wire the effects of heating rate were also analyzed. Recrystallization of the 18 mil wire is characterized by rather gradual changes in hardness, resistivity ratio, and microstructure leading to a small recrystallized grain size. The 0.178 mm wire, on the other hand, exhibits more abrupt changes in resistivity ratio and hardness which coincide with the development of a recrystallized structure having a large grain-size range. Variation of heating rates between about 150,000°C/min and 500°C/min did not significantly affect the grain structure or hardness achieved for annealing temperatures of 2000°, 2500°, and 2700°C. However, very slow heating rates, less than 10°C/min, were shown to prevent the formation of large grains in the 0.178 mm wire. These results are explained on the basis of differences in the effectiveness of ThO₂ particles in hindering grain boundary motion.     

脉冲激光切丝工艺制备球形钼粉

为了获得高性能的实心球形颗粒钼粉原料,采用脉冲激光切丝法制备球形钼粉。通过筛分、光学显微镜和扫描电子显微镜等研究了所制备钼粉的粒度、形貌、微观组织等物理性能。结果表明,脉冲激光切丝法制备的钼粉形貌呈球形或近球形,表面光滑,没有卫星颗粒或颗粒粘接聚集现象。在试验工艺参数范围内,90%以上的钼粉颗粒粒径在150 μm以上,其中粒径在150～300 μm范围的颗粒占比最大,超过60%。粒径400 μm以下的钼粉通常是内部致密的,而在一些粒径较大的钼粉颗粒中出现内部孔洞,并初步分析了钼粉颗粒及其内部孔洞的形成机制。     

溶胶-凝胶法制备纳米稀土镧掺杂钼粉

采用液-液掺杂方式将仲铝酸铵、硝酸镧以及柠檬酸溶液混合,采用溶胶-凝胶法制备纳米稀土镧掺杂钼粉.研究初始溶液pH值和柠檬酸添加量对成胶效果的影响,讨论干凝胶的除胶工艺,分析稀土镧在掺杂铅粉中的存在形式.结果表明:当初始溶液的pH值为1且柠檬酸的添加量为仲钼酸铵质量的1.5倍时,可制备出疏松多孔、网状结构、成胶效果良好的干凝胶.采用直接烧结法在560℃焙烧可将胶体很好地除去,两段还原后得到颗粒为球形且十分均匀的纳米掺杂Mo粉.在掺杂MoO3粉中,镧以La2O3或La-Mo复合氧化物形式存在,稀土颗粒粘附在MoO3颗粒表面.在MoO3的还原过程中La-Mo复合氧化物分解,镧以La2O3的形式存在于Mo粉中.钼粉颗粒尺寸在500 nm左右,掺杂La2O3的尺寸约100nm.     

The high temperature creep behavior of doped tungsten wire

The creep behavior of 0.018 cm diam doped tungsten wire has been studied over a range of stress from 30 to 90 MPa and temperature from 2400 to 2800 K. Grain aspect ratio (gar) had a strong influence on creep and rupture of the recrystallized wires, and separated the creep behavior into two regimes with a transitional gar of about 11 between the two. The low gar regime showed lower strength and characteristics typical of grain boundary sliding. In the high gar regime, properties were independent of gar, and evi-dence is presented to show that creep is governed by dislocation-bubble dispersion strengthening. Formerly with the Lamp Business Division of General Electric Company, E. Cleveland, Ohio     

Dopant particle characterization and bubble evolution in aluminum-potassium-silicon-doped molybdenum wire

The present article describes the creation of dopant inclusions in aluminum-potassium-silicon (AKS)-doped molybdenum powder and the generation of potassium bubbles in doped molybdenum wire. Molybdenum wire is used extensively in the incandescent lamp industry for coiling mandrels, filament support wires, and foil seals. The AKS-doped molybdenum wire is an important product, because it possesses greater high-temperature strength and a higher recrystallization temperature than undoped molybdenum; both of these properties are important for structural applications in lamps. The AKS-doped molybdenum wire is produced in a similar manner to AKS-doped tungsten wire, but lower processing temperatures are typically used for the production of molybdenum wire. Previous studies on AKS-doped tungsten wire have shown that the dispersion which provides the interlocking grain structure in recrystallized tungsten wire is bubbles of elemental potassium; these enhance incandescent lamp filament life. However, there is little previous work on the potassium-containing dispersion in AKS-doped molybdenum wire. In AKS-doped molybdenum, the dispersion can be either potassium bubbles, or solid oxide particles, depending on the processing method. This article will describe a series of analyses of doped molybdenum wire and its precursors, namely, doped powder and sintered ingots. The roles of high- and low-temperature sintering are also described.     

Porosity and anomalous recrystallization behavior in doped tungsten wire

An anomalous recrystallization behavior has been observed in 0.010 in. diam K?Si?Al doped tungsten wire. Recrystallization to relatively equiaxed grains occurred only in the core at temperatures of 1400° to 1600°C, but not at lower temperatures or higher temperatures up to 1900°C. The anomalous recrystallization reaction was suppressed when the wire was preannealed at 1700° to 1900°C, but not by preanneals at temperatures between 500° and 1100°C. Critically shadowed electron fractographs indicated that linear arrays of microporosity (≈100Å diam) were responsible for the stabilization of the fibrous structures, Recrystallization occurred when these strings of pores were absent.     

Si、Al、K掺杂钼丝的组织和性能研究

通过透射电镜(TEM)、扫描电镜(SEM)、能谱分析(EDS)对Si、Al、K掺杂烧结钼条和退火钼丝的组织形貌进行了跟踪检测分析;通过DSC和硬度试验检测Si、Al、K掺杂钼丝的再结晶温度;通过热模拟试验对纯钼条和Si、Al、K掺杂钼条的高温综合力学性能进行了对比分析.结果表明:Si、Al、K掺杂使钼条的高温综合力学性能得到了明显的改善;在本试验条件下,Si、Al、K掺杂使钼丝的再结晶温度提高约550～600℃,再结晶后由长径比大的晶粒形成燕尾搭接状链锁结构组织;Si、Al、K掺杂钼丝的强化相是K泡和硅酸铝钾颗粒.     

The identification of second phases within bubbles in annealed doped tungsten wire

Elemental potassium was detected within bubbles formed in annealed, commercially doped tungsten wire by transmission electron microscopy and selected area diffraction. The bubbles in specimens which had been annealed in hydrogen contained liquid potassium, solid potassium, and small quantities of potassium hydride. Only solid potassium was observed within bubbles when specimens were annealed in < 10^-5 mm Hg vacuum. The potassium solidified epitaxially on the tungsten bubble surface and had virtually the same lattice orientation. The potassium hydride usually displayed a specific orientation relationship with the solid potassium and the tungsten.     

The recrystallization of commercially pure and doped tungsten wire drawn to high strain

The recrystallization processes in both undoped and doped tungsten wire after drawing to a true strain of 7.7 were examined by light microscopy and transmission electron microscopy. High angle grain boundary migration commenced at approximately the same temperature in both materials, but proceeded much more rapidly in the undoped wire, where the absence of a potassium bubble dispersion allowed a coarser, more equiaxed grain structure to form. No change from the (110) deformation texture was observed in either case. Recrystallization in the undoped wire was dominated at lower temperatures (1100 to 1200°C) by the growth of large grains into a much finer structure. As the annealing temperature was increased, this process was replaced by a general grain coarsening which eventually produced a relatively equiaxed recrystallized grain structure. It appeared probable that it was the second phase dispersion inhibition alone that prevented similar structural changes in the doped wire. This paper is based on a presentation made at a symposium on “Recovery Recrystallization and Grain Growth in Materials” held at the Chicago meeting of The Metallurgical Society of AIME, October 1977, under the sponsorship of the Physical Metallurgy Committee.     

Si和La元素对Mo丝显微组织与力学性能的影响

系统研究了La、Si单元掺杂和复合掺杂对钼丝的显微组织和力学性能的影响及其作用机制,优化出具有优异力学性能的Mo-Si-La合金丝的成分为Mo-0.15Si-(0.5～0.8)La.MoSi2与Mo原位反应生成Mo5Si3和Mo3 Si硬质相,起到良好的晶粒细化作用和弥散强化作用.La2O3颗粒通过延迟微裂纹的形成和扩...     

The effect of wire history on the coarsened substructure and secondary recrystallization of doped tungsten

This article reports a study of primary and secondary recrystallization in tungsten wire. Samples with two different processing histories were annealed in the electron emission microscope, and the recrystallization process was followed. The fibers produced by drawing were first observed to widen and break up into shorter lengths. As the temperature was raised, the secondary recrystallization occurred in a characteristic, stepwise motion, with the secondary grain moving from one position to the next and then remaining pinned at the new position, sometimes for the entire length of the test. It was found that the temperature at which secondary recrystallization occurred depended on the heating rate. If a slow heating rate was used, the temperature at which secondary recrystallization occurred would be higher. This result was interpreted to mean that the slower heating rate allowed more strain to be annealed out of the wire before secondary recrystallization occurred and thus lowered the driving force for this process. The secondary recrystallization temperature could not be correlated with the primary grain structure or differences in the potassium bubble distribution in the wire. The primary recrystallized grain structures of the two wires were also different, and this difference, too, was attributed to differences in the amount of stored energy in the wire at the start of the annealing. It was also shown that even though the bulk potassium content of the two wires was the same and the bubble distributions in the two wires were similar, the bubble distributions in the ingots were different.