掺杂对钽丝组织和性能影响的研究

通过金相显微分析和扫描电镜观察,研究了掺杂对钽条和钽丝组织和性能的影响.结果表明:随着掺杂量的增加,钽条晶粒变细,且掺B比掺A细化晶粒的效果更加明显,但随着掺B量的增加烧结变得不充分,钽条密度降低;随着掺杂量的增加,钽丝的再结晶温度升高,组织晶粒细化,其中掺B比掺A细化效果更加明显;烧结不充分和退火不完全再结晶是造成掺杂钽丝生产过程中毛刺和坑点产生的主因.     

拉丝钽条的真空烧结

拉丝钽条的真空烧结是钽丝加工生产过程的重要关键工序,其目的在于净化杂质、致密金属而提高其强度.由于氧化钽介电常数高且稳定性良好,故以钽材(钽粉丝)为主要原材料制作的或电解电容器(结构见图1)已成为众多工业部门必须之重要电子元件.钽丝质量直接影响到钽电容器的质量.我国原采用电子轰击-冷加工制取钽丝,由于其晶粒粗大抗氧脆性差,阳极块烧结时钽丝脆断,这是我国钽电容器生产以来存在的“老大难”问题.钽丝长期由西德、日本进口;1983年601厂采用粉末冶金-冷加工法生     

钽粉掺杂对低氧钽表面的钽氧化物质量的影响

虽然电容器级钽中添加微量的掺杂元素如P、B、S等,可以抑制表面扩散,防上烧结时粉末表面积出现的有关损耗,从可增加单位重量的电容量,提高电容器的效率。但是,钽粉掺杂后,由于热氧化物厚度比较低的钽表面发生意想不到的化学反应,使钽氧化膜的质量大大降低。这种情况在电容器钽引线接头中比较常见。如果不好好了解这种现象,则可能将这种不良电介质膜混入电容器,从而影响其性能和可靠性。     

氢化钽粉烧结方式对钽丝加工过程及其性能的影响

对钽丝用冶金级钽粉原料组成之一的氢化粉的烧结方式进行研究.以真空垂熔烧结和热处理炉辐射式烧结两种方式生产得到氢化粉,按同种比例分别调配得到两种冶金级钽粉原料,分析对比了两种原料的化杂、物性,以及生产的钽丝性能.试验结果表明:两种方式烧结的氢化粉调配的冶金级钽粉原料,化杂及物性没有明显差异,生产的钽丝化杂及物性水平接近,...     

NiO掺杂对菱镁矿烧结性能的影响

以天然菱镁矿为原料,添加不同质量分数的NiO粉末,采用高温煅烧法制备了镁砂。利用显气孔体密测定仪、X射线衍射仪、扫描电子显微镜分析NiO粉末掺杂对镁砂熟料烧结性能、物相组成、微观结构的影响。结果表明,在菱镁矿中添加NiO粉末有利于提高镁砂烧结致密性,促进MgO晶粒长大。当不添加NiO粉末时,试样在1600℃烧结前后线变化率为8.72%,体积密度为2.96 g·cm-3,显气孔率为19.2%,MgO晶粒尺寸为1.36 μm;当加入质量百分数为0.75% NiO粉末时,试样烧结前后线变化率为18.06%,制备镁砂体积密度为3.29 g·cm-3,显气孔率为11.5%,MgO晶粒尺寸为3.81 μm。在1600℃对添加NiO粉末的菱镁矿进行烧结,NiO可以与MgO完全固溶,引起MgO晶格畸变,降低晶体活化能,提高MgO烧结致密性能。但添加过多NiO,在短时间内无法与MgO完全固溶,妨碍烧结相的直接接触,影响传质过程,导致样品烧结性能降低。     

低压烧结对硬质合金组织和性能的影响

通过配制不同粒度的WC粉末,分别在低压和真空条件下烧结制备WC-6Co硬质合金,采用扫描电镜分析、光学金相检测、显微硬度试验、钴磁检测、矫顽磁力检测和抗弯强度检测等方法,对比研究了低压烧结和真空烧结制备的硬质合金的显微组织和性能。结果表明,与真空烧结相比,低压烧结有效地降低了合金的孔隙度,增大了合金的密度,提高了合金的综合性能;低压烧结对合金的组织和性能的影响程度与原料WC粒度有关,低压烧结对粗颗粒WC为原料的合金的综合性能提高不明显。     

掺杂与钽丝毛刺的关系研究

通过金相显微分析、扫描电镜观察和力学性能测试研究了掺杂对钽条和钽丝组织和性能的影响, 分析了在钽丝生产过程中毛刺产生的原因.结果表明: 烧结不充分和退火再结晶不完全是造成钽丝生产过程中毛刺和坑点产生的主因; 随着掺杂量的增加, 钽条晶粒变细, 且掺B比掺A细化晶粒的效果更加明显, 但随着掺B量的增加烧结变得不充分, 钽条密度偏低; 随着掺杂量的增加, 钽丝的再结晶温度升高, 组织晶粒细化, 其中掺B比掺A细化效果更加明显; 随着掺杂量的增加钽丝室温抗拉强度增加, 延伸率则随着掺A量的增加而降低, 随着掺B量的增加而升高, 且掺B较掺A强化效果明显, B的加入还起到了细晶韧化效果.     

掺杂Si-Al-K对钼粉及其烧结制品组织、性能的影响

研究了不同含量掺杂元素对钼粉形貌、烧结坯及钼丝微观组织的影响。研究表明，随着掺杂元素含量的升高，钼粉粒度逐步细化：在烧结过程中，掺杂元素在烧结坯形成非晶相的第二相粒子，并且随着掺杂元素含量的升高，第二相粒子的分布密度增大，使烧结坯晶粒得到细化；在加工过程中，烧结坯中的第二相粒子碎化为粒子串，粒子串分布于纤维晶界处，可改善钼丝性能。     

影响烧结钽坯料致密度的因素

采用金属钽粉为原料,通过冷等静压成型、真空垂熔烧结、轧制、拉拔等粉末冶金加工工艺制取电容器级钽丝。金属钽粉的微观形貌、粒度分布及化学成分等粉末特性,以及钽坯料加工过程及成型与烧结工艺过程特性,直接影响烧结后钽坯料的致密度,也将直接影响电容器级钽丝的理化性能。研究表明：钽粉的平均粒径在5.5～6.5μm时有利于钽坯料的烧结;钽粉的化学杂质含量高、等静压压力小、烧结炉的气氛差等因素不利于钽坯料的致密。     

高氧钽粉配碳生产低氧钽条的工艺研究

对高氧钽粉生产低氧钽条工艺进行了研究,结果表明：采用高氧钽粉配碳预烧结、还原的方法可以生产出低氧优质钽条,与镁处理法相比,该法工艺简单、节能降耗,经济效益明显。     

元素粉末预合金化对烧结合金钢组织和性能的影响

为充分发挥合金元素提高铁基烧结材料强度的作用,加快我国中、高强度铁基粉末冶金产品的发展,通过试验分析比较了混合粉、部分(扩散)预合金粉、完全预合金粉对镍钼铜合金钢显微组织和力学性能的影响。结果表明:显微组织取决于成分的分布均匀性,其中Ni和C的均匀性影响最大;混合粉烧结钢的显微组织主要由珠光体、铁素体构成,部分预合金粉烧结钢的显微组织由珠光体、铁素体、贝氏体和马氏体组成,完全预合金粉烧结钢的显微组织主要为铁素体基体上分布碳化物颗粒;经过部分预合金化和完全预合金化后,材料的力学性能有明显提高,淬火态抗弯强度分别为968MPa和1027MPa,冲击韧性分别为26J/cm2和30J/cm2。     

Structure and some properties of sintered tantalum carbide

Conclusions A study was made of the microstructure, transverse rupture strength, and electrical resistivity of tantalum carbide specimens produced by sintering at various temperatures. It is shown that, to obtain sintered tantalum carbide of fine-grained structure, low porosity, and adequate strength, it is necessary to employ very fine starting powders. Raising the sintering temperature and increasing the duration of isothermal holding lower the porosity and electrical resistivity of sintered tantalum carbide, but at the same time induce substantial grain growth.Translated from Poroshkovaya Metallurgiya, No. 11(239), pp. 76–79, November, 1982.     

Influence of CeO2 doping amount on property of BCTZ lead-free piezoelectric ceramics sintered at low temperature

Ba0.85Ca0.15Ti0.9Zr0.1O3(BCTZ) lead-free piezoelectric ceramics co-doped with CeO2(x=0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%) and Li2CO3(0.6 wt.%) were prepared by conventional solid-state reaction method. Influence of CeO2 doping amount on the piezoelectric properties, dielectric properties, phase composition and microstructure of prepared BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM) and other analytical methods. The results showed that the sintered temperature of BCTZ lead-free piezoelectric ceramics doped with CeO2 decreased greatly when Li2CO3 doping amount was 0.6 wt.%; a pure perovskite structure of BCTZ lead-free piezoelectric ceramics co-doped with Li2CO3 and CeO2 and sintered at 1050 °C could also be obtained. The piezoelectric constant(d33), the relative permittivity(εr) and the planar electromechanical coupling factor(kp) of BCTZ ceramics doped with Li2CO3 increased firstly and then decreased, the dielectric loss(tanδ) decreased firstly and then increased and decreased at last when CeO2 doping amount increased. The influence of CeO2 doping on the properties of BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were caused by "soft effect" and "hard effect" piezoelectric additive and causing lattice distortion. When CeO2 doping amount(x) was 0.2 wt.%, the BCTZ ceramics doped with Li2CO3(0.6 wt.%) and sintered at 1050 °C possessed the best piezoelectric property and dielectric property with d33 of 436 pC/N, kp of 48.3%, εr of 3650, tanδ of 1.5%.     

Electrical conductivity and microstructure of sintered ferrous materials: sintered iron

Abstract

The viability of electrical conductivity as a tool for describing the microstructure of sintered iron compacts was investigated, the sintering temperature being varied from dewaxing to high temperature sintering. The relationships between formation of sintered contacts, presence of lubricants, and mechanical properties were evaluated through determination of conductivity and effective load bearing cross-section A_c . The latter parameter was measured via quantitative fractography of specimens impact fractured at 77 K. The role of porosity and sintering temperature on grain growth in iron was also evaluated using quantitative metallography. It was found that the conductivity of pressed compacts increases during the dewaxing stage, while the effect of the sintering parameters at higher temperatures is less conspicuous. In any case, the conductivity can be related to the load bearing cross-section by a logarithmic equation. Using the already established relationships between A_c and the mechanical properties, the latter can be predicted by using the conductivity, which might be helpful in quality control of PM components.     

高温退火和添加Si对仿M10铁基烧结合金显微组织的影响

在一种仿M10粉末冶金铁基烧结合金显微组织中出现了针状碳化物,通过高温退火和添加Si元素的方式研究了针状碳化物的演变特征.采用X射线衍射和能谱分析确认了这是一种M2C型碳化物.结果表明：M2C是一种稳定性较高的亚稳相,高温退火时Mo、Cr、V元素向基体内扩散使M2C可以断裂、球化和分解.提高退火温度能加快针状碳化物形貌和结构的转变.Si元素可进入更稳定的M6C型碳化物中,抑制M2C的形成,显微组织中针状和块状碳化物共存.     

Effects of Pr-Cu-Ti intergranular addition on microstructure and magnetic properties of heavy-rare-earth-free Nd-Fe-B sintered magnets

By intergranular addition of Pr-Cu-Ti alloy powders in the Nd-Fe-B sintered magnets with the normal B component, we propose an approach to the optimization of grain boundary and local Nd-Fe-B composition system. The coercivity is enhanced from 1.42 to 1.86 T, while further addition leads to a reduction in remanence and coercivity. The analyses of phase composition reveal that Ti mainly exists in the form of metallic Ti alloy, and part of Ti combines with B to form the TiB₂ phase after the liquid phase sintering process. This process results in a consumption of B in the local Nd-Fe-B composition system and a change of the grain boundary component, which contributes to the formation process of the RE₆(Fe,M)₁₄ phase after the annealing process. Therefore, with the modification of grain boundary and composition system, the intergranular addition of Pr-Cu-Ti induces the generation of continuous thin grain boundary phases. It promotes the intergrain exchange decoupling, increasing the coercivity in the annealed magnet. While the excess addition results in the segregation of TiB₂, as well as the precipitation of TiB₂ into the Nd-Fe-B phase, which leads to structural defects. Thus, the further effort for the addition alloy with Ti to reduce the deterioration of the microstructure will lead to further improvement in magnetic properties.     

合金元素对汽车减震器活塞组织与性能的影响

为了将轴承滚动体研磨钢泥制得的还原铁粉应用于汽车减震器活塞的生产中,在其中加入石墨、电解铜粉及羰基铁粉等制成合金粉末,并压制、烧结成型,通过正交试验探讨石墨、电解铜粉及羰基铁粉质量分数对试样组织和性能的影响。结果表明,碳对硬度和抗拉强度的影响最大,铜的影响较小;随石墨和铜粉质量分数的增大,铁素体减少,珠光体增多;得出成分为Fe-1.2C-1.8Cu-10羰基铁粉的合金符合汽车减震器铁基粉末冶金零件技术条件JB/T 9138-1999的要求。