高温钛合金Ti-60粉末的制备和表征

采用感应熔炼气体雾化法制备了掺杂稀土Nd的高温钛合金Ti-60粉末。结果表明,在制备过程中合金元素几乎没有烧损,增氧量小于100×10~(-6);粉末的平均粒度(d_(50))约为100μm,满足正态分布,雾化气体的压力增大则粉末的粒度减小;粉末的形貌大多呈球形,只有少量的形状不规则;部分粉末是空心的,其比例随着粉末粒度的增加而增大;粉末表面有明显的凝固特征,具有清晰的二次枝晶;随着Nd含量的增加,粉末表面富Nd稀土相的析出增加;粉末由针状α′马氏体组织构成,当真空退火温度超过700℃时马氏体开始微量分解,当温度升高到850℃时马氏体大量分解。     

四硼酸锶(SrB_4O_7)的制备新工艺及其影响因素

采用液相沉淀法合成两种水合硼酸锶SrB₂O₄ ?4H₂O和SrB₆O₁₀ ?5H₂O, 将其高温煅烧制备出纯四硼酸锶(SrB₄O₇)相, 分析了高温煅烧过程、产物的物相和形貌, 研究了煅烧温度和保温时间等因素的影响。结果表明, 在加热过程中水合硼酸锶发生脱水 → 非晶化→ 晶化过程, 且SrB₆O₁₀在800℃左右分解为SrB₄O₇和液态氧化硼; 将SrB₂O_4  ?4H₂O和SrB₆O_10 ?5H₂O在900℃煅烧4 h可制得纯相四硼酸锶; 延长煅烧时间可提高产物的晶化程度, 但是其晶型没有明显的变化。 用该法制备的SrB₄O₇:Eu荧光粉, 其发光强度明显比以SrCO₃和H₃BO₃为原料制备的样品高。     

Preparation of sulfonated poly (phthalazinone ether ketone ketone) and properties of the composite membranes SPPEKK/BPO4

通过亲核缩聚反应合成含二氮杂萘酮结构的磺化聚芳醚酮酮(SPPEKK), 并经原位复合制备了磺化聚芳醚酮酮/磷酸硼(SPPEKK/BPO₄)复合质子交换膜. 用核磁共振谱(¹H--NMR)和FT--IR光谱表征纯膜及其复合膜结构, 研究了BPO₄的含量对复合膜的保水能力、热稳定性能、质子传导率以及复合膜中BPO₄稳定性能的影响. 结果表明, 随着BPO₄含量的增加, SPPEKK/BPO₄的复合质子交换膜质子传导率逐渐增大. 当BPO₄含量达到30\%时, 质子传导率达到6.3 ×10^-2 S/cm(90℃). 用原位生成法制备的SPPEKK/BPO₄在保持一定尺寸稳定性和热稳定性的前提下, 膜的导电性能明显改善.     

水雾化法制备FeSiCr软磁合金粉末研究

采用水雾化法制备FeSiCr软磁合金粉末,系统研究了熔体温度、雾化压力及雾化水流量对合金粉末粉体性能的影响。利用激光粒度分析仪、扫描电子显微镜、氧氮分析仪和霍尔流量计等设备对粉末粒度、形貌、氧含量、松装密度及流动性进行测试、分析。研究结果表明:随着雾化压力和熔体温度的升高,粉末粒度逐渐变小;降低雾化水流量,制备的粉末形貌较为规则,粉末粒度减小、松装密度得到提高。最佳雾化工艺:雾化压力为50 MPa、熔体温度为1 750 ℃、水流量为15.24 L/min,制备的FeSiCr软磁合金粉末氧含量低,平均粒度小且形貌较规则。     

纳米晶合金粉芯的超重力渗流制备及磁性能

为了探索粉芯的新制备工艺,以Fe73.5Cu₁Nb₃Si13.5B₉纳米晶合金铁芯为原料,使用机械破碎法制粉,并采用超重力渗流工艺制备了7种不同粒度配比的纳米晶合金粉芯,借助SEM、XRD、VSM分别对纳米晶粉末的形貌、结构和磁性能进行了表征,研究了粉末粒度配比对纳米晶合金粉芯的形貌、密度、有效磁导率、损耗及品质因数的影响。结果表明,机械破碎法制得的粉末虽带尖角,但矫顽力低,利用超重力渗流工艺制备的粉芯其粉末表面基本被树脂完全包覆。同时,通过适当的粉末粒度匹配,发现性能最佳粉芯的粉末粒度配比为:100~200目占60%,200~400目占20%,400~1 000目占20%。该种粉芯的密度为4.46 gcm³,在100~3 000 kHz频率范围内有效磁导率比较稳定,且在3 000 kHz时为28.2。当设定磁感应强度为20 mT,频率为500 kHz时,其损耗为99.1 W/kg。另外,根据实验结果可知,该工艺能够制备出频率在MHz以上具有较低损耗的粉芯。     

Investigation of self-assembly growth and thermal stability of Au nano-particles on atomic-layer-deposited Al2O3 film

在原子层淀积的Al₂O₃薄膜表面自组装生长Au纳米颗粒,研究了Au纳米颗粒的自组装过程和热稳定性. 结果表明,原子层淀积的Al₂O₃薄膜表面很容易吸附氨丙基三甲基硅烷(APTMS), 有利于Au纳米颗粒的自组装, 生长出的Au纳米颗粒尺寸为5--8 nm, 密度约为4×10¹¹cm^-2. 在300℃氮气中退火使Au纳米颗粒的尺寸增大, 但是没有改变APTMS的吸附状态和Au的化学组成. 当退火温度提高到450℃时, Au纳米颗粒发生明显的团聚, 且分布变得极不均匀.     

直流等离子体法制备Cu纳米粉

本实验利用直流等离子体法制备了Cu纳米粉末,并系统研究了工艺参数对Cu纳米粉末粒子产率、粒径和粒径分布规律的影响。正交实验、扫描电子显微镜、产率及粒径分析结果表明:Cu纳米粉末粒子最佳制备工艺参数为电流(380±5) A、制粉室内N₂气体比例为(15±2)%、风机转速为2 400～2 500 r/min。在此工艺条件下获得的Cu纳米粉末粒子呈球形,Cu纳米粉末粒子粒径分布均匀,分布范围较窄,粒径约为100 nm。随着N₂气体比例增加,电流强度增大,Cu纳米粉末产率提高,但同时会导致Cu纳米粉末粒子平均直径增大、粒径分布变宽。然而,随着轴流风机转速的提高,Cu纳米粉末产率提高,并且Cu纳米粉末粒子平均直径减小、粒径分布变窄,这与较快的转速引起Cu棒表面原子蒸气浓度下降有关。     

导液管内径对SnAgCu系无铅焊锡雾化粉末特性的影响

利用自行设计的超音速雾化制粉装置,研究了导液管内径对SnAgCu系无铅焊锡粉末有效雾化率、粒度分布及球形度的影响.结果表明:在一定雾化条件下,导液管内径为3mm,雾化粉末具有较高的有效雾化率、粒度分布及离散度最佳,且球形度最好;随着内径的减小,粉末明显细化,有效雾化率略有增加,但粒度分布变差;随着导液管内径的增大,粉末有效雾化率急剧降低,粒度分布变差,且表面粗糙,形状不规则.     

保护气氛对Fe80Si9B11非晶带材表面特征及磁性能的影响

非晶合金带材的表面特征对磁性能有着重要的影响。为研究CO保护气氛对Fe₈₀Si₉B₁₁非晶带材表面鱼鳞纹的形成及非晶合金带材磁性能的影响规律,本文采用平面流铸法制备了Fe₈₀Si₉B₁₁非晶合金带材,利用金相显微镜、X射线衍射仪和磁性能测试仪研究了熔潭保护气体CO流量对非晶合金带材表面特征、微观结构及磁性能的影响。研究表明,不同CO流量条件下制备的合金带材均为非晶态,且CO流量对带材厚度几乎无影响;随CO流量增大,熔潭周围气体密度和气压降低,熔潭稳定性增强,裹入熔潭的气体变少,带材贴辊面气泡尺寸变小且数量减少,带材表面的鱼鳞纹间距增大。当CO流量为0时,带材表面比较粗糙,观察不到鱼鳞纹;当CO流量为0.25和0.5 m³/h时,带材表面鱼鳞纹间距分别为1.5、2.3 mm。随CO流量增大,由于气泡对畴壁的钉扎和鱼鳞纹细化磁畴的协同作用,使带材矫顽力和铁损降低,振幅磁导率增大;磁损耗分离结果表明,随CO流量增大,磁滞损耗降低,涡流损耗增大,且铁损降低主要由磁滞损耗降低引起的。     

氩气雾化Ti6Al4V预合金粉末的制备及特性研究

采用氧气雾化法制备出Ti6Al4V预合金粉末,并对粉末的粒度分布、形貌和微观结构进行了研究.结果表明:所制备的粉末颗粒细小,粒度呈正态分布.粉末大部分为球形或近球形,粉末表面为近似六边形胞状组织,大颗粒粉末表面相对较为粗糙,并伴有少量的卫星颗粒,小颗粒粉末表面光滑,并且没有黏附卫星颗粒.粉末的内部组织呈现为胞状结构,组织细小均匀.粉末主要由α相胞晶和细针状马氏体α ′组成,这都是快速凝固所形成的;随着粉末粒度的减小,针状相数量和尺寸减小,并且部分发生球化形成细小的球化相.粉末表面存在一定的成分偏析以及碳、氧元素污染,氧化膜的厚度约为30μm.     

功率对EIGA制备3D打印用TC4合金粉末特性的影响

与传统的雾化制粉技术不同,电极感应熔炼气体雾化(EIGA)技术是采用预合金棒料为电极,无坩埚感应加热,熔化后直接滴落雾化区被惰性气体雾化的技术.该技术由于在熔炼过程中液态金属与坩埚不接触,有效地减少了钛合金粉末中的夹杂物,改善了合金粉末的质量.本文利用自主设计制造的EIGA制粉设备,采用激光粒度分析仪、扫描电镜(SEM)、X射线衍射仪(XRD)等分析手段,研究了不同功率参数对雾化制备TC4合金粉末的粒度分布、组织形貌、空心球等的影响.研究表明:EIGA法制备的TC4合金粉末整体球形度均较好,空心球缺陷较少,空心球率低于3%.熔炼功率较低时,粗颗粒粉末较多,且存在一定比例不规则的棒形和哑铃状粉末颗粒;当功率提高到62 k W时,细粉比例明显提高,不规则形状的粉末颗粒基本消失.随着功率的升高,粉末中的氧含量呈增加趋势,但仍基本保持在0.08%~0.10%较低范围内.功率为56 k W时,粉末松装密度最好,为2.686 g/cm3,松装密度比为60.63%,符合激光3D打印用TC4钛合金粉末松装密度比要求.     

Undercooling and supersaturation of alloying elements in rapidly solidified Al-8.5% Fe-1.2% V-1.7% Si alloy

Dispersion-strengthened Al-8.5% Fe-1.2% V-1.7% Si alloy was produced by inert gas atomization and atomized melt deposition processes. Differential scanning calorimetry was used to estimate the extent of undercooling in the alloy powders as a function of powder size and in the atomized melt-deposited alloy as a function of process parameters. The estimated undercooling was found to be a strong function of powder size and processing conditions and varied from 380–200 °C. Alloy powders of diameter greater than 180 jam did not experience any undercooling during solidification. X-ray diffraction analysis was performed to study the dependence of supersaturation of alloying elements and metastable phase formation on the extent of undercooling. When the undercooled alloy was heated to about 400 dgC, formation of Al₁₂(Fe, V)₃Si phase with b c c crystal structure from the supersaturated matrix was observed.     

La2O3-Y2O3-ZrO2纳米陶瓷粉末的制备及高温相稳定性

用化学共沉淀法制备4.5%Y2O3-ZrO2(YSZ)和0.6%La2O3-YSZ、0.8%La2O3-YSZ、1.2%La2O3-YSZ(0.6La、0.8La、1.2La)(摩尔分数)纳米复合陶瓷粉末,研究了四组粉末的高温相稳定性.结果表明:采用正向滴淀方法制备的0.6La粉末(粒径～50 nm)团聚严重,而用反向...     

Microstructures and mechanical responses of powder metallurgy non-combustive magnesium extruded alloy by rapid solidification process in mass production

Spinning Water Atomization Process (SWAP), which was one of the rapid solidification processes, promised to produce coarse non-combustible magnesium alloy powder with 1–4 mm length, having fine α-Mg grains and Al₂Ca intermetallic compounds. It had economical and safe benefits in producing coarse Mg alloy powders with very fine microstructures in the mass production process due to its extreme high solidification rate compared to the conventional atomization process. AMX602 (Mg–6%Al–0.5%Mn–2%Ca) powders were compacted at room temperature. Their green compacts with a relative density of about 85% were heated at 573–673 K for 300 s in Ar gas atmosphere, and immediately consolidated by hot extrusion. Microstructure observation and evaluation of mechanical properties of the extruded AMX602 alloys were carried out. The uniform and fine microstructures with grains less than 0.45–0.8 μm via dynamic recrystallization during hot extrusion were observed, and were much small compared to the extruded AMX602 alloy fabricated by using cast ingot. The extremely fine intermetallic compounds 200–500 nm diameter were uniformly distributed in the matrix of powder metallurgy (P/M) extruded alloys. These microstructures caused excellent mechanical properties of the wrought alloys. For example, in the case of AMX602 alloys extruded at 573 K, the tensile strength (TS) of 447 MPa, yield stress (YS) of 425 MPa and 9.6% elongation were obtained.     

气雾化法制备金属粉末的研究进展

气雾化技术所制备的粉末粒度细小、球形度高、氧含量低、具有快速冷凝组织结构,具备大规模生产的能力且成本低,是目前生产高性能球形金属及合金粉末的主要方法.论述了气雾化技术的基础原理及特点,综述了气雾化用各类喷嘴结构、气体流场结构及工艺参数对粉末特性的影响,概述了新型气雾化介质和混合雾化方法等新进展,并指出了该技术由于存在缺乏理论指导、缺乏设计标准等问题,其发展滞后于金属粉末生产行业的发展.     

Synthesis of SnO2 hollow microspheres from ultrasonic atomization and their role in hydrogen sensing

Nanostructured SnO₂ hollow microspheres were synthesized using ultrasonic atomization technique. It is interesting that hollow microspheres could be prepared from ultrasonic atomization technique without any aid of template and surfactant. X-ray powder diffraction (XRD) confirmed the material to be SnO₂ having tetragonal structure. Average crystallite size calculated from X-ray diffractogram using Scherer's equation was found to be 8.45 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the microscopic study of fine powder particles. Powder consists of hollow microspheres of average diameter of 0.58 μm as well as nanoparticles of average diameter of 6 nm. The sensors fabricated from such powder show high hydrogen (1000 ppm) response (S = 2379) under the optimized experimental conditions. Sensor performance merits, such as, high hydrogen response, high hydrogen selectivity, short response time (2 s) and quick recovery time (15 s) may be due to both nanocrystallites and hollow microspheres associated in SnO₂ sensing material. The dramatic change in gas response was explained by the rapid diffusion of the target gas through the nano-porous structure of SnO₂ hollow microspheres.     

On the Temperature-Induced Equilibration of Phase Distribution and Microstructure in a Gas-Atomized Titanium Aluminide Powder

Powder production by gas atomization of γ-TiAl based alloys typically yields a highly nonequilibrium material regarding the occurring phases and their microstructural appearance. In particular, the equilibration of the powder and the associated phase transformations during heating are of great importance for the subsequently applied densification techniques. The present work employs in situ high-energy X-ray diffraction to investigate how this thermodynamic equilibration manifests itself in the resulting phase distribution, the ordering behavior of the disordered α and β phase, both evidenced in the powder, and the change of the γ lattice parameters during heating of a Ti–46.3Al–2.2W–0.2B (at%) powder up to 850 °C. Complementary microstructural characterization of the gas-atomized powder and the heat-treated material condition reveals that the temperature exposure predominately affects the dendritic parts of the microstructure, especially when the α phase is transformed into γ phase with small embedded grains of α₂ and β_o.     

软磁合金粉末特性对金属软磁粉芯的影响

软磁合金粉末作为制备金属软磁粉芯的原材料,是决定磁粉芯性能的关键因素之一。本文综述了软磁合金粉末的合金成分、形貌、粒度以及粉末纯度对软磁粉芯性能的影响。分析结果表明,铁硅铝磁粉芯具有最佳性价比,采用气雾化法生产的球形粉末具有最佳的软磁特性,软磁粉末越细,纯度越高,所制备的磁粉芯软磁性能越好。     

Design of powder metallurgy aluminium alloys for applications at elevated temperatures Part 1 Microstructure of high pressure gas atomized powders

Abstract

A method is described for designing powder metallurgy rapidly solidified aluminium alloys using experimental and/or calculated nucleation maps which give the microstructure of gas atomised powders as a function of powder particle size and alloy composition. This method was used to predict the compositions of Al–Cr–Zr–Mn alloys for which the <45 μm sizefraction of the gas atomised powders exhibits a microstructure with or without Al₁₃Cr₂ intermetallic particles. Powders were produced by high pressure gas atomisation and were examined using analytical electron microscopy. The microstructures observed were in excellent agreement with those predicted. The powders exhibited four distinct microstructures with increasing powder particle diameter: (i) segregation free, (ii) cellular α aluminium, (iii) α aluminium plus fine spherical precipitates rich in chromium and manganese, and (iv) α aluminium plus Al₁₃Cr₂ primary intermetallic particles. The solidification of these powders is discussed in terms of solidification front velocity controlled by external heat flow and by the initial undercooling. Particles less than 10 μm in diameter undercool significantly before solidification. Segregation free microstructures occur in the fine <1 μm) particles, where the solidification front velocity exceeds the absolute stability velocity.

MST/1247a     

CoCrFeMnNi high‐entropy alloy powder with excellent corrosion resistance and soft magnetic property prepared by gas atomization method

To successfully fabricate high‐entropy alloys by powder metallurgy, laser cladding, or thermal sprayed method, the high‐entropy alloy powders possessing good homogeneous microstructure are very important. However, the study on the properties of the high‐entropy alloy powder has still been lacking. In this work, an equiatomic CoCrFeMnNi high‐entropy alloy powder with spherical shape was synthesized by gas atomization method. The as‐atomized CoCrFeMnNi high‐entropy alloy powder is composed of a single face‐centered cubic solid solution phase with the particle size of 34.0 μm. Furthermore, the as‐atomized powder exhibits excellent corrosion resistance in 10 % hydrochloric acid solution to 304 L stainless steel powder, and also shows an excellent soft magnetic behavior. Therefore, the gas atomization method can be used to generate other kinds of high‐entropy alloy powders for many challenging industrial applications.