金属包套与镍基粉末冶金高温合金之间连接区的研究

本文通过观察金属包套与粉末冶金高温合金之间连接区形貌,分析了在镍基粉末冶金高温合金毛坯表面发现明显原始颗粒形貌的原因,重点研究了不锈钢包套与镍基粉末冶金高温合金之间的连接区。结果表明:连接区内在不锈钢和粉末冶金高温合金之间存在明显的界面,界面两侧存在扩散层,距离界面最近的镍基高温合金粉末仍保持原始粉末颗粒形貌;毛坯表面发现原始颗粒形貌是靠近粉末冶金高温合金一侧的界面没有完全去除造成的;界面、界面附近粉末原始颗粒形貌的形成与C扩散及镍基高温合金粉末元素偏析有关,连接区Ⅰ厚度不小于167μm,连接区Ⅱ厚度不小于716μm。     

粉末高温合金中原始粉末颗粒边界研究进展

原始粉末颗粒边界(prior particle boundary,PPB)是粉末高温合金(powder metallurgy superalloy,P/M superalloy)中常见的缺陷之一,它是在制粉期间以及热等静压或热挤压前期的加热过程中,在原始粉末表面处析出的一层细小且连续的第二相网膜;这层析出物可能会阻碍粉末颗粒间的扩散与连接,成为了合金中的薄弱界面,严重破坏合金组织,危害其拉伸、冲击等各项力学性能。本文着重介绍了目前针对粉末高温合金中原始粉末颗粒边界的研究进展,重点概述了影响原始粉末颗粒边界的形成因素及消除措施。     

Fe-Mo-B Enhanced Sintering of P/M 316L Stainless Steel

Liquid-phase enhanced sintering of powder metallurgy（P/M）316L stainless steel by addition of sintering aids was studied.2%-8% of pre-alloyed Fe-Mo-B powder with two different particle sizes was added as sintering aids,and the specimens were sintered in vacuum at 1 200-1 350 ℃.The results show that the fine Fe-Mo-B powder（5-10 μm）has stronger activated effect.The sintered density increases with the increase in sintering aid content or sintering temperature.Warm compaction has a better effect on the control of dimensional precision of compacts.The prealloyed Fe-Mo-B powder deviated from Mo2FeB2 component can also be sintering aid of P/M 316L stainless steel.     

氩气雾化法制备FGH96高温合金粉末颗粒的凝固组织

利用扫描电镜(SEM)对氩气雾化(argon gas atomization,缩写AA)工艺制备的FGH96高温合金原始粉末颗粒的粘结形式、凝固组织、表面和内部形貌及其形成机理进行研究.结果表明:AA法制备的FGH96合金粉末,在颗粒尺寸d≥40 μm时,颗粒之间出现凸起式粘结、包覆式粘结以及葫芦式粘结,其中凸起式粘结...     

Influence of Size of Hematite Powder on Its Reduction Kinetics by H2 at Low Temperature

The reduction kinetics and mechanisms of hematite ore with various particle sizes with hydrogen at low temperature were studied using the thermogravimetric analysis. At the same temperature, after the particle size of powder decreases from 107.5 μm to 2. 0 μm, the surface area of the powder and the contact area between the powder and gas increase, which makes the reduction process of hematite accelerate by about 8 times, and the apparent activation energy of the reduction reaction drops to 36.9 kJ/mol from 78.3 kJ/mol because the activity of ore powder is improved by refining gradually. With the same reaction rate, the reaction temperature of 6. 5 μm powder decreases by about 80 ℃ compared with that of 107.5 μm powder. Thinner diffusion layer can also accelerate the reaction owing to powder refining. The higher the temperature, the greater is the peak of the reduction rates at the same temperature, the greater the particle size, the smaller is the peak value of the reduction rates both inner diffusion and inter-face chemical reaction play an important role in the whole reaction process.     

机械力促进碳粉气化反应

 研究了机械力对碳粉物理化学性能的影响规律。发现在球磨过程中,碳粉的颗粒度及晶粒不断细化、比表面积不断增大,当颗粒度小于40 μm时,碳粉的晶粒大部分为100 nm左右的纳米晶粒。当作用时间较长时,碳粉会发生无定形化。在机械力的作用下,晶粒会产生畸变和位错,从而形成活化中心,降低反应活化能;同时由于碳粉比表面积的增大,增加了反应物与碳粉的接触面积,从而有利于加快气化反应的进行。与传统粉体(小于150 μm)相比,细化后碳粉(小于40 μm)的气化温度下降200 ℃左右。     

低温下氢气还原氧化铁的动力学研究

 用热重分析法研究了低温下不同粒度氧化铁的氢还原动力学,得出在同一温度下,铁矿粉粒度从107.5 μm降到2.0 μm后,由于粉体的表面积大幅度增加,提高了粉气接触面积,从而使得化学反应的速度提高了8倍左右,还原反应的表观活化能从78.3 kJ/mol降低到36.9 kJ/mol;当反应速度相同时, 粒度6.5 μm的粉体的反应温度比107.5 μm的降低了80 ℃左右。同时,通过理论推导和实验结果表明,当反应扩散层厚度相同时,铁矿粉粒度越小,反应扩散层厚度越薄,其还原率越高。     

Milling of Carbide-Steel Powder Components and Their Mixtures in an Attrition Mill

Milling of wear-resistant steel and titanium carbide powders is studied with an attrition mill rotation rate of 980 rpm. The physical and technological properties of powders and particle size are determined. Particle shape and the change in material chemical composition during milling are studied. It is established that steel powder cannot be milled to particle sizes less than 3.6 μm whereas a mixture of steel and titanium carbide can be milled to a fine state (0.3 μm). Powders with a size of about 1 μm neither flow nor are formable. Use of benzene as a milling medium makes it possible to prevent steel powder oxidation, but the carbon content in titanium carbide decreases. During milling of the main part of the charge to a fine state rather large steel particles (up to 50 μm) remain.     

复合助磨剂对钢渣超微粉助磨效果

以乙二醇与三乙醇胺为原料、无水乙醇为溶剂配制复合助磨剂。将复合助磨剂分别与滚筒渣、脱硫渣和热闷渣进行混合后,利用行星式球磨机进行粉磨。研究钢渣的化学成分与矿物组成、不同助磨剂对钢渣超微粉粒度分布的影响、复合助磨剂对钢渣超微粉的作用机理。结果表明,当乙二醇、三乙醇胺与无水乙醇按体积比2∶2∶2配制复合助磨剂,以钢渣∶复合助磨剂质量体积比为450 g∶6 mL时,钢渣超微粉的粒度分布最佳,即d90为9.14~9.28、d50为3.31~4.20、d10为0.99~1.04和d90-d10为8.11~8.24 μm,其中复合助磨剂对脱硫渣的助磨效果最佳。     

超细煤系煅烧高岭土粉体制备的工艺参数优化

以盘式搅拌磨为超细粉碎设备,系统地研究了粉碎法制备超细煤系煅烧高岭土粉体的工艺参数。结果表明,矿浆浓度、磨矿时间、研磨介质添加量和配比、叶轮搅拌速度是制备超细煤系煅烧高岭土粉体的重要工艺参数,合理地选择这些工艺参数。才能制备出粒度-2μm、含量大于90%的超细煤系煅烧高岭土粉体。     

等离子旋转电极雾化制备钨粉及性能表征

采用等离子旋转电极雾化技术(PREP)制备球形钨粉,利用激光粒度分析仪、氧氮分析仪、扫描电子显微镜(SEM)对钨粉末的粒径分布、氧含量、微观形貌、表面组织进行分析。结果表明：球形钨粉粒度集中分布在45～150μm,呈单峰分布,理论中位粒径85.5μm与实测粒径80μm接近。钨粉氧增量均小于0.001 5%,其中45～150μm粉末比15～53μm的粉末氧增量更低,仅为0.000 38%。15～53μm钨粉表面光洁,几乎无空心粉。钨粉物理性能优异,且粒径在45～150μm的钨粉性能优于15～53μm的。     

Magnetic Properties of Nanocrystalline Powder Cores Fabricated by Mechanically Crushed Powders

Fe73.5Cu1Nb3Si15.5B7 nanocrystalline powder cores with different particle sizes ranging from 10 to 125μm were fabricated by cold-pressing techniques.The cores exhibited increased core loss Pcvand decreased initial permeabilityμiwith addition of fine powders below 50μm in size,and the content should be less than 40mass%.It was thought to be closely related to the high coercive force Hcdue to the stresses generated during the crushing process and high demagnetization fields of small powders.Furthermore,modifying the alloy compositions by adding defined amount of Ni could improve the soft magnetic properties,including superior characteristics of permeability under high direct current(DC)bias field and comparable low core loss at high frequency.     

基体铜的粒度对铜基粉末冶金摩擦材料性能的影响

采用粒度为270、150、106和75μm的气雾化纯铜粉作为基体,通过粉末冶金热压烧结的方式,制备铜基摩擦材料.研究基体铜的粒度对材料的物理力学性能、材料组织和摩擦性能的影响.采用MM-3 000摩擦磨损试验机测试3 000~7 000 r/min转速条件下材料的摩擦性能,结果表明:铜粉粒度从270μm减小到75μm时,材料的流动性变差,压坯密度降低,材料的硬度呈减小趋势,从18.5 HBW降到14.0 HBW.但是铜粉粒度为106μm时,硬度反而增加为2.0 HBW.随着转速的升高,摩擦系数呈先增加后减小的趋势,粒度为106μm的试样摩擦系数比较稳定,摩擦系数变化从0.336到0.348,磨损率也最低,在7 000 r/min初速度下仅为47 mg.     

PREP工艺参数对FGH95高温合金粉末特性的影响

研究了采用等离子旋转电极工艺制取FGH95高温合金粉末时各主要工艺参数对粉末平均粒度及其分布的影响。粉末的平均粒度主要取决于棒料的转速，且随棒料转速的增加而减小。粉末粒度的分布则与棒料转速、等离子弧电流强度以及等离子枪与棒料端部的距离等工艺参数有关。提高棒料转速、减小等离子弧电流强度或等离子枪与棒料端部的距离，均可使粉末粒度的分布范围变窄。     

Characteristics and printability of K417G nickel-base alloy powder prepared by VIGA method

Nickel-based K417G superalloy powder is the main material used in laser additive manufacturing (LAM) of aerospace engine turbine blades. In this study, K417G powder was prepared by the vacuum induction melting gas atomisation method (VIGA). Powder characteristics and microstructure were measured, and the properties of fabricated samples were studied. The results show that the powder mean particle size D₅₀ was 74?μm, flowability was 16.6?s/50?g, apparent density was 4.78?g?cm^–3, and the oxygen content of the powder was 0.015%. Powder and LAM sample microstructure consisted of γ, γ′, and carbide. The average microhardness was 410?HV, tensile strength was 1080?MPa, yield strength was 828?MPa and elongation was 13.52%. K417G superalloy powder prepared by VIGA method has potential for application in laser additive manufacturing.     

粒度可控氧化钇粉体的制备

以硝酸钇为原料溶液,采用氨水-草酸2步沉淀法合成了中心粒径（D₅₀）为1.00~2.00 μm的氧化钇粉体,粉体分散性好,粒度可控.考察了沉淀剂的浓度、物料的浓度、反应温度、加料速度以及pH值等因素对氧化钇粉末中心粒度的影响.采用激光粒度仪、比表面仪、扫描电子显微镜等仪器对实验过程及实验结果进行表征和分析.结果表明,在氨水浓度为1.0 mol/L、草酸质量浓度为10 %、滴加速度为20 mL/min、草酸溶液温度为80 ℃、氨水沉淀后pH值在7~8之间、草酸转化后pH值小于1的条件下,可通过调节硝酸钇的浓度在0.4~0.8 mol/L之间,以制备中心粒径（D₅₀）在1.00~2.00 μm范围内、比表面积在3.2~13.3 m2/g之间的氧化钇粉体.      

Sintering of aluminum powders in air in the presence of silumin and KAlF<Subscript>4</Subscript> flux: Model experiments

The role of a KAlF₄ flux and the effect of its particle size on the sintering process of a PA-4 aluminum powder are investigated. A dispersed flux is more effective. In model experiments, the mechanisms of flux spreading over the surface of aluminum are established. On sintering an aluminum powder of particle size d > 60 μm, it is recommended to use a flux with particle size d < 50 μm at its total content of 1–3%.     

热挤压对FGH96镍基粉末高温合金微观组织的影响

研究了热挤压温度、挤压比、挤压速度、挤压前预处理对FGH96镍基粉末高温合金微观组织的影响规律,确定了获得晶粒尺寸小于10 μm的超塑性细晶组织的热挤压方法.研究结果表明,热等静压后FGH96合金发生了再结晶,实现了粉末的完全致密化成形,但晶粒大小极不均匀,且存在明显的原始颗粒边界(PPB)缺陷.采用热挤压前预处理工艺...     

铝粉粒度和烧结温度对硅太阳能电池铝背场结深及光电转化率的影响

分别采用4种不同粒度(平均粒度为1.37、3.95、6.08和9.73μm)的铝粉制备单晶硅太阳能电池铝浆,研究铝粉粒度和烧结温度(800、830、850和870℃)对铝背场结深和光电转化率的影响。结果表明:采用不同粒度的铝粉在相同条件下制备的铝背场,经800℃烧结后,结深均为4.05μm左右,其中粒度为6.08μm的铝粉,其光电转化率最高,达到17.2%;烧结温度从800℃升高到870℃时,铝背场结深从4.05μm增加到4.75μm,转化率略有提高。     

超高转速等离子旋转电极工艺制备钬铜球形粉末的研究

采用超高转速等离子旋转电极工艺(supreme-speed plasma rotating electrode process, SS-PREP)制备韧性金属间化合物钬铜(HoCu)球形粉末, 粉末粒度在15~106μm之间。利用X射线衍射仪、扫描电子显微镜、能谱分析及光学显微镜分析了SS-PREP钬铜球形粉末的粒度分布、松装密度、振实密度及霍尔流速等粉末特性, 比较了不同试验方法对粒度分布的表征。结果表明, SS-PREP钬铜粉末主要由CsCl结构的RM型B2相构成, 不同粒度的HoCu球形颗粒化学成分基本一致, 随着粉末粒度增大, HoCu球形粉末的非球形颗粒比例呈现下降趋势。