两种电场快速烧结方法制备W-Cu合金的对比研究 “研究生论坛”稿件，投稿栏目为“研究生论坛”

为了解决传统烧结方法制备W-Cu合金存在的烧结温度高、烧结时间长、晶粒长大严重等缺点,利用电场对材料烧结的促进作用,本文采用放电等离子烧结（SPS）和大电流电阻烧结两种电场快速烧结方法制备W-Cu合金。借助阿基米德排水法测量密度和金相显微镜、扫描电镜等分析测试方法,对两种电场快速烧结方法在不同烧结温度条件下（800℃、900℃、1000℃）制备的W-20wt%Cu合金的致密化程度及显微组织结构进行了对比研究。通过对两种烧结方法中电场密度的计算和烧结体显微组织结构中铜池的出现,结果表明：在本实验条件下,相比放电等离子烧结法,采用大电流电阻烧结法在加热过程中更容易产生场致发射效应,这有利于W-Cu合金组织的均匀分布,促进烧结致密化。大电流电阻烧结体的相对密度和显微组织结构均优于放电等离子烧结体;采用放电等离子烧结,烧结温度从800℃提高到900℃时,烧结体的相对密度增大,合金内部孔洞和晶粒的大小、分布更加均匀,但当烧结温度达到1000℃时,烧结体的相对密度增幅不大,烧结体孔洞集中,且晶粒团聚;而在大电流电阻烧结时,随着烧结温度升高,烧结体的相对密度增大,显微组织结构的均匀性也得到提高。     

热压烧结法制备钨铜复合材料的工艺研究

铜钨复合材料是以铜、钨元素为主的一种两相结构假合金,广泛应用于电接触材料,电子封装和热沉材料.作者研究了采用轴向热压烧结来制备纳米W-15%Cu复合材料的方法,分析了工艺参数对该复合材料性能的影响及其影响机理.实验为获得超细晶粒显微组织和优异均匀性纳米W-15%Cu复合材料提供了重要的实验基础和依据.     

高能球磨钨基高密度合金超细粉末的烧结

研究了采用行星式高能球磨机球磨后的９７Ｗ－２Ｎｉ－１Ｆｅ（质量分数，％）高密度合金混合粉末的特性和烧结行为，实验结果表明，球磨可以生成纳米晶粉末和Ｗ的超饱和固溶体，产生大量的缺陷，促进烧结致密化，在１２５０￣１４２０℃固相烧结时可以达到几乎全致密和得到非常细的晶粒。作者还对烧结过程中出现的问题进行了初步探讨。     

Electrical Breakdown Characteristic of Nanostructured W-Cu Contacts Materials

Nanostructured （ NS ）W-Cu composite powder was prepared by mechanical alloying （ MA ）, and nanostructared bulk of W-Cu contact material was fabricated by hot press sintering in an electrical vacuum furnace. The rnicrostructure, electric conductivity, hardness and break down voltage of NS W- Cu alloys were measured and compared to those of conventional W-Cu alloys prepared by powder metallurg＇y. The experimental results show that microstructural refinement and uniformity can improve the breakdown behavior and the electric arc stability of nanostructared W- Cu contacts materials. Also, the wanostructured W- Cu contact material shows the characteristic of spreading electric arcs, which is of benefit to electric arc erosion.     

贮氢合金的应用研究进展

本文概括了新型功能新料－贮氢材料的发展状况和应用研究进展，重点综述了稀土储氢合金性能改善方面的最新成果和用于二次电池的贮氢材料的状况。     

低钴粗晶Wc—Co合金的烧结

分析了不同烧结工艺条件对低钴粗晶Ｗｃ－Ｃｏ合金性能的影响,证实了利用真空烧结提高低钴粗晶Ｗｃ－Ｃｏ合金性能的可行性。     

激光烧结LaMg_2Ni_9合金相结构和电化学性能

探讨激光烧结功率对烧结LaMg_2Ni_9贮氢合金相结构和电化学性能的影响。结果表明,激光烧结LaMg_2Ni_9合金由LaNi_5,LaMg_2Ni_9和MgNi_2三相组成。随激光功率的提高LaMg_2Ni_9相的产率提高。600,1000 W激光烧LaMg_2Ni_9合金的放电容量分别为101.1,85.3(mA·h)/g。1000 W激光烧结的LaMg_2Ni_9合金组织细小均匀,具有较好的循环稳定性。     

纳米Fe-Ni合金晶须制备及表征

采用液相还原法通过在不同反应温度和反应物浓度条件下,以KBH4为还原剂,在二价铁、镍盐的水溶液中加入适量的表面活性剂还原出晶须状的Fe-Ni合金.用XRD衍射技术和TEM电镜测试手段,进行了合成Fe-Ni合金的物相分析和晶须形貌的表征.结果表明:液相还原反应可以得到6 nm的Fe-Ni合金晶须,当溶液浓度为1.0 mol/L时,晶须平均尺寸最小,长径比最大,晶须的成须率好.     

机械合金化法制备W-Cu合金粉末的研究

将W80Cu20（n（W）：n（Cu）=4：1）混合粉末在QM-BP式行星式高能球磨机中球磨进行机械合金化,研究了不同球磨时间对W-Cu混合粉末组织的影响.采用XRD和SEM对不同球磨时间的粉末进行分析,结果显示随着球磨时间的增加,混合粉末产生合金化效果不断增强,Cu固溶于W中,并且晶粒尺寸得到一定的细化.     

Microstructure and Properties of W-Cu Alloys Prepared with Mechanically Activated Powder

W-15% Cu (mass fraction) alloys were sintered with mechanically activated powder in order to develop new preparing processes and improve properties of alloys. The microstructures of the activated powder and the sintered alloy were observed. Properties such as density were measured. The results show that through mechanical activation, the particle size of the powder becomes finer to sub-micron or nanometer level, some copper was soluble in tungsten, and high density W-Cu alloys can be obtained by mechanically activated powder for its action to the activation sintering.     

Manufacture of high-dispersed W-Cu composite powder by mechano-thermal process

In order to improve the process of co-reduction of oxide powder, a new mechano-thermal process was designed to produce high-dispersed W-Cu composite powder by high temperature oxidation, short time high-energy milling and reduction at lower temperature. The particle size, oxygen content and their sintering abilities of W-Cu composite powder in different conditions were analyzed. The results show that after a quick milling of the oxide powder for about 3-10 h, the reduction temperature of the W-Cu oxide powder can be lowered to about 650 ℃ from 700-750 ℃ owning to the lowering of particle size of the oxide powder. The average particle size of W-Cu powder after reduction at 650 ℃ is about 0. 5μm smaller than that reduced at 750 ℃. After sintering at 1 200℃ for 1 h in hydrogen atmosphere, the relative density and thermal conductivity of final products (W-20Cu) can attain 99. 5% and 210 W ·m-1· K-1 respectively.     

Kinetic characteristics of liquid phase sintering of mechanically activated W-15wt% Cu powder

The kinetic characteristics of W grain growth operated by diffusion controlled Oswald ripening （DOR） during liquid phase sintering were studied. A liquid phase sintering of W-15wt%Cu was carried out by pushing compacts into a furnace at the moment when the temperature increased to 1340℃ for different sintering times. The results show that liquid phase sintering produces the compacts with considerably low relative density and inversely, rather high homogeneity. On the basis of the data extracted from the SEM images, the kinetic equation of W grain growth, G^n = G0^n ＋ kt, is determined in which the grain growth exponent n is 3 and the grain growth rate constant k is 0.15 μm^3/s. The cumulative normalized grain size distributions produced by different sintering times show self-similar. The cumulative distribution function is extracted from the curves by non-linear fitting. In addition, the sintering kinetic characteristics of W-15wt%Cu compacts were also investigated.     

高能球磨时间对钨铜复合材料性能的影响

将W-15wt%Cu粉在行星式高能球磨机中进行球磨,并将球磨粉末加压烧结成型。研究了不同球磨时间对钨铜复合材料性能的影响。采用XRD、SEM对所制备的球磨粉末及烧结合金分别进行物相分析和组织形貌观察,并测定了烧结合金的相对致密度。结果表明,随着球磨时间的增加,钨铜球磨粉末晶粒尺寸得到细化,且有不饱和固溶体产生;烧结合金晶粒尺寸长大,孔洞减少,相对密度增大接近全致密。     

电解充氢及退火热处理与ZL114合金的力学性能

充氢后的铝合金试样在空气中放置一段时间后，其力学性能与充氢前比不降反升.由此想到，若将充氢试样进行退火热处理，可望获得更佳的效果.以ZL114为试验合金，对比测定了在空气中放置和退火后的试样与原来的充氢试样的力学性能，观察了它们的断口形貌.为缩短试验周期、突出试验结果，便于对比，采用了浓度为1?mol/L的HCl溶液.结果表明，退火热处理明显改善了充氢试样的延伸率和缩面率，断口中出现韧窝状凹坑.因此，可用此法快速析出试样中的氢，减轻及消除氢对其力学性能的影响.     

PREPARATION OF AMMONIUM PARATUNGSTATE WITH COARSE GRAIN BY EVAPORATING CRYSTALLIZATION

Evaporatingcrystallizationiswidelyusedtoprepareammoniurnparatungstate(APT)crystalfromindustrialammoniumtungstatesolution.Usually,anammoniumtungstatesolutionwithdensityof1'20--1.28g.cm--3(aboutWO,250--280g.l--l)isevaporatedinanenamelreactorat80--90Cfor6--8htocrystallizeoutarnmoniumparatungstatecrystalswithapparentdensityof1'0--1.4g.cm--3.Intherecentyears,manyusersathomeandabroadhavestrictqualityrequirmentnotonlyinchemicalcompositionbutalsoinphysicalproperties,includingparticle--sizeanddistrib…     

A new technology for production of high purity paratungstate ammonium from low grade tungsten concentrate

A new technological process for production of paratungstate ammonium from low grade tungsten concentrate with a high content of calcium and impurities has been studied. The experiments show that average tungsten leaching efficiency of more than 96.92% can be obtained with a low NaOH consumption by using the mechanical activating caustic decomposition, and the content of main impurities (P, As, Si) in Na₂WO₄ solution obtained is competitive with that from standard wolframite concentrate by traditional caustic decomposition. After recovering caustic soda by crystallization, impure Na₂WO₄ solution is changed to (NH₄)₂WO₄ solution by ion exchange method. Molybdenum may be removed from (NH₄)₂WO₄ solution by new ion exchange method. Finally, paratungstate ammonium of high purity is obtained. This technology has the advantages of short technological process, high recovery of tungsten, high economic and social benifits. Synopsis of the first author Sun Peimei, professor, born in 1945, specializing in rare metallurgy and hydrometallurgy.