快速凝固Ml（NiCoMnTi）5击剑锪组织结构与电化学性能

本文对比研究了快速凝固和常规熔铸Ｍｌ（ＮｉＣｏＭｎＴｉ）５合金的组织结构和电化学性能。ＳＥＭ和ＸＲＤ分析研究表明,冷却速度较慢的常规熔铸合金为粗大的树枝晶组织,合金中Ｍｎ偏析明显,并且有少量ＴｉＮｉ３第二相组成。但在冷却速度高达１０＾５－１０＾６Ｋｓ＾－１快速凝固条件下,合金的组织转变为细小的柱状晶,合金呈ＣａＣｕ相结构,并使Ｍｎ的成分偏析得到抑制。     

超音速气体雾化高硅铝合金粉末冷却速度计算

通过快速凝固技术制备合金材料,可以大幅度细化合金组织,其技术的冷却速度.本文通过对流换热原理对超音速气体雾化高硅铝合金粉末的冷却速度进行了理论计算,结果表明其冷却速度大约在104～107K/s之间,说明利用超音速气体雾化制备高硅铝合金粉末可以达到很高的冷却速度;另外,通过测定合金粉末内部凝固枝晶间距,并利用冷却速度和枝晶间距之间的经验关系,确定合金冷却速度,其结果与理论计算基本相符.     

凝固条件和镁对Al-Si11.0合金组织的影响

研究了宇向凝固时冷却条件和镁元素对Ａｌ－Ｓｉ１１．０合金树枝晶结构和共晶组织的影响。试验结果表明,随着冷却速度的增加,Ａｌ－Ａｉ１１．０合一次枝晶和二镒分枝间距都显著减小,在较小的冷却速度时,加入镁元素后合金的二镒分枝间距明显增大,而在冷却速度大于１６０Ｋ／ｍｉｎ时,则没有影响。试验还发现,加入镁元素后,冷却速度对共晶成分的影响显示减小,是合 共晶组织变细。在试验范围内,Ａｌ－Ｓｉ１１．０合金中加     

快速凝固Al—Ti合金的再结晶

本文研究了快速凝固Ａｌ－Ｔｉ合金的再结晶行为,探讨了增强相Ａｌ３Ｔｉ颗粒对合金再结晶进程的影响。增强体Ａｌ３Ｔｉ的存在促进再结晶晶粒形核,增大再结晶驱动力,从而降低再结晶激活能,加速Ａｌ－Ｔｉ合金再结晶的进程。     

激光快速凝固Al—Mn合金的组织选择规律研究

利用５ｋＷＣＯ２激光器对Ａｌ－１．１,３．２和５．６ｗｔ％Ｍｎ合金进行了一系列表面重熔实验,并对微观组织形成规律进行了研究。实验结果表明：重熔区组织较基体组织大大细化;Ａｌ－３．２ｗｔ％Ｍｎ在所有速度范围内没有明显的共晶生长出现,而以α（Ａｌ）胞／枝晶形式生长;随着生长速度的增大,Ａｌ－５．６ｗｔ％Ｍｎ合金的组织由Ａｌ６Ｍｎ枝晶向α（Ａｌ）＋Ａｌ６Ｍｎ共晶、α（Ａｌ）胞／枝晶及完全无偏析固溶体转烃     

RS／PMAl－Fe－MRE耐热粉末铝合金成形工艺、组织与性能的研究

研究了ＲＳ／ＰＭＡｌ－Ｆｅ－ＭＲＥ耐热铝合金的粉末成形工艺、组织与性能的关系。粉末尺寸越小，组织越细，得到的力学性能越好。随着ＭＲＥ含量的增加，力学性能增加。同尺寸粉末合金，氦气作冷却介质时，其力学性能较氩气作冷却介质的要好。采用本试验粉末合金成形工艺制得的Ａｌ－Ｆｅ－ＭＲＥ粉末耐热铝合金，具有优异的室温及高温力学性能     

快速凝固高阻尼Al—Zn—Mg—Cu系合金的研究

本文研究了利用快速凝固粉末冶金工艺制备高阻尼Ａｌ－Ｚｎ－Ｍｇ－Ｃｕ系合金。通过拉伸性能与阻尼性能的测试，以及显微组织分析，探讨了纯铝及石墨对合金拉伸性能及阻尼性能的影响。结果表明：Ａｌ－Ｚｎ－Ｍｇ－Ｃｕ／１５ｗｔ％Ａｌ合金的室温拉伸性能已达到ＬＣ９ＣＧＳ１的水平，阻尼性能为Ｑ＝６．０×１０＾－３；在室温至３００℃温度范围内，随着温度的升高，合金的阻尼能力提高；合金的阻尼机制属复合型机制。     

双级雾化快速凝固工艺及其破碎机理

设计制造了由超音速气体雾化和旋转盘雾化组成的双级雾化装置，并对比有雾化处理进行分析，提出了旋转盘机械破碎模型。采用Ａｌ－２０Ｓｉ合金进行了工艺性试验，并采用Ａｌ－４．５Ｃｕ合金地该装置的冷却速度进行了测算。     

Ti—25Al—10Nb—3V—1Mo合金的高周疲劳性能及断裂特征

实验测定了Ｔｉ－２５Ａｌ－１０Ｎｂ－３Ｖ－１Ｍｏ合金６５０℃下高周疲劳Ｓ－Ｎ曲线及热暴露后合金的疲劳性能。结果表明，Ｔｉ－２５Ａｌ－１０Ｎｂ－３Ｖ－１Ｍｏ合金具有较高的疲劳强度，可以满足转子零件的要求。对比光滑和缺口试样的高周疲劳性能，可以看出该合金缺口敏感程度高，且随着应力水平的增加而增大。     

Ti—47Al—2Mn—2Nb—0.8TiB2合金的动态拉伸性能

采用自制的Ｈｏｐｋｉｎｓｏｎ拉杆装置,在２０＾－１０＾３ｓ＾－１应变速率范围内了近全片层组织Ｔｉ－４７Ａｌ－２Ｍｎ－２Ｎｂ－０．８ＴｉＢ２合金的拉伸力学性能。发现动态强度明显高于静态强度,前者与应变速度之间遵循线性关系,后者遵循半对数线性关系;室温塑性随应变速率变化而波动,变化范围不大。     

Effect of gas Mach number on the flow field of close-coupled gas atomization,particle size and cooling rate of as-atomized powder: Simulation and experiment

Gas velocity is a key parameter regulating the particle size and the cooling rate of the gas atomized powder applied in additive manufacturing, metal injection molding, thermal spraying, and soft magnetic composites. In this paper, on basis of the well-designed close-coupled nozzles with different gas Mach numbers at the outlet, the gas field structure was simulated by Computational Fluid Dynamics (CFD) software, and the process of cooling and solidification of Fe-6.5 wt% Si metal droplets was calculated by finite difference method. The results show that with the increase of Mach number, both the gas velocity downstream and the pressure at the base of melt delivery tube tip rise, whereas the mass flow rate of the melt decreases. The nozzles with high Mach number can produce finer powder with higher cooling rate. The median diameter of the powder prepared by the nozzle with Mach numbers of 1.0, 1.5, 2.0, and 2.5 is 44.9, 39.0, 32.5, and 29.1 μm, respectively, and the corresponding cooling rate of the metal droplet with a diameter of 80 μm is 2.85 × 10⁴, 2.98 × 10⁴, 3.32 × 10⁴, and 3.50 × 10⁴ K/s, respectively. This work provides new ideas and suggestions for the preparation of metal powder with small particle size at high cooling rate.     

Increasing the amorphous yield of {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 powders by hot gas atomization

The synthesis of metallic glasses requires high cooling rates leading to product size limitations of a few millimeters when using conventional casting techniques. One way to overcome these size limitations is powder metallurgy. Melt atomization and the subsequent powder processing can result in larger, amorphous components as long as no crystallization takes place during powder consolidation.An iron-based glass-forming alloy {(Fe_0.6Co_0.4)_0.75B_0.2Si_0.05}₉₆Nb₄ was formed through both ambient room and high temperature inert gas atomization at various melt flow rates (close-coupled atomization). The use of hot gas generally decreases the droplet size and hence leads to an increased cooling rate and amorphous fraction of the atomized powders.Hot gas atomization results in a lower gas consumption, a smaller gas-to-melt mass flow ratio (GMR), smaller particles and a smaller geometric standard deviation.Particles atomized in ambient temperature were fully amorphous up to a particle size fraction of 90?µm. Larger particle size fractions resulted in a higher crystalline fraction. According to the XRD and DSC analyses, hot gas atomization has only a very small influence on the cooling rate and the amorphous fraction. However, the amorphous yield is significantly increased using hot gas atomization.     

Powder discharge from a hopper-standpipe system modelled with CPFD

In this paper, computational particle fluid dynamic (CPFD) modelling approach was used to describe the discharge of a fine glass beads powder from different hopper-standpipe geometries. The comparison between the CPFD predictions and the experimental results in terms of solid discharge rates, surface cone shape during discharge and pressure drops in the standpipe. The comparison allowed to assess on the possibility to use the CPFD modelling approach to simulate the powder flow in the hopper-standpipe system even accounting for the rather complex interactions between the interstitial gas and the particles occurring in the presence of a standpipe. Furthermore, the effect of hopper geometry on powder discharge was investigated with the CPFD model and verified experimentally in some purposely built hoppers. Finally, the relationships between the hopper geometry parameters (hopper outlet diameter and hopper half angle) and the flow parameters (solid discharge rate, height of characteristic surface, particle volume fraction, particle velocity, gas pressure and flow pattern) were obtained.     

Preparation of Ultrafine Si Powders from SiH_4 by Laser-induced Gas Phase Reaction

High quality ultrafine Si powders have been synthesized from SiH4 by laser induced gas phase reaction. The powders prduced under different synthesis conditions have mean particle size of 10-120nm in diam. with narrow particle size distribution, and free of hard agglomerates.The powders are polycrystalline with the ratio of mean grain to particle diameter being between 0.3-0.7. The size of the powder increases with increasing laser power and reaction pressure,but decreases with increasing silane gas flow rate and the addition of Ar diluent. Grain sizes drop distinctly with the rise of the addition of Ar gas and laser power, but change little with the gas flow rate and reaction temperature. The formation of Si particles under different synthesis conditions is discussed     

EIGA法制备激光3D打印用TA15钛合金粉末

采用电极感应熔炼气雾化(EIGA)法制备了激光3D打印用TA15钛合金粉末,研究了熔炼功率对粉末收得率、粒径分布、粉末形貌、松装密度和流动性等特征的影响。结果表明,随着感应熔炼功率增大,粉末收得率和平均粒径减小,当熔炼功率为65kW时,粉末收得率超过62%,中值粒径D_(50)小于100μm,松装密度为2.731g/cm3,流动性为22.46s/50g。对粒径50~180μm的粉末采用激光3D打印,激光直接沉积成形的TA15钛合金样品表面无宏观裂纹和气孔等缺陷,金相组织为细晶网篮组织,制备的TA15钛合金粉末具有良好的可打印性。     

一种新型的雾化方法

固体雾化是一种新型的制粉方法 ,通过改变雾化介质可以改善雾化效果。本文介绍固体雾化的理论依据及总结固体雾化的主要特征 ,研究表明在同等气体压力和流量的条件下 ,采用含有固体颗粒盐的高速气流对金属液体和合金进行雾化破碎 ,所得粉末比不含固体颗粒盐的高速气流制得的粉末 ,粒度细的多 ,粉末粒度分布窄 ,粉末冷却速度较大     

Solidification behaviour of Pd–Rh droplets during spray atomization

Solidification microstructure in spray-atomized Pd–10 wt% Rh powders using high-pressure gas atomization was studied. The solidification cooling rate and the solidification front velocity were investigated using a transient heat-transfer finite element method. Two different atomization gases, nitrogen and helium, were considered in the modelling studies. On the basis of the results obtained, it was found that gas atomization using helium gas led to solidification cooling rates and solidification front velocities which were two times higher than those obtained using nitrogen gas. Moreover, the cooling rate and the solidification front velocity increased with decreasing powder size for both types of atomization gas. The numerically estimated solidification front velocity using finite element analysis for nitrogen gas atomization was found to be smaller than the analytically determined absolute stability velocity that is required to promote a segregation-free microstructure. This was noted to be consistent with the segregated microstructure that was experimentally observed in nitrogen gas atomized powders. In the case of helium gas atomization, however, the increased cooling rate and solidification front velocity are anticipated to promote the formation of a segregation-free microstructure in the gas-atomized powders. This revised version was published online in November 2006 with corrections to the Cover Date.     

AEROSOL DELIVERY FROM AN ACTIVE EMISSION MULTI-SINGLE DOSE DRY POWDER INHALER

All commercially available dry powder inhalers depend solely on the patient's inspired airflow to aerosolize the drug formulation. The dose delivered is therefore subject to inter-patient variability that may be overcome by devices actively imparting energy to the powder bed to disperse particles. The current studies were performed to evaluate powder filling and dose delivery from a prototype active emission multi-single dose dry powder dispersion device. The device contained interchangeable cartridges (12 doses/cartridge, three cartridges with dosing chamber diameters of 0.5, 1.0, and 1.5 mm, each 6mm in length) which were vacuum filled with the powder formulation. Individual doses were emitted by compressed gas propulsion following actuator depression. Studies were performed using bulk lactose powders (~25-100 and ~ 40-200μm); and sieved lactose (45-75 and 75-125μm), alone and in 2% albuterol sulfate blends. Vacuum fill flow rates of 7, 14, 21, and 28 L/min were used. Filled cartridges were inserted into the device and emitted masses determined gravimetrically. Aerodynamic particle size measurements and fine particle fractions were determined by inertial impaction (8-stage Andersen impactor, 60L/min). Powders filled at a flow rate of 28L/min exhibited a high packing density and were delivered as a pellet. Consequently, lower flow rates of 7, 14, and 21 L/min were used to evaluate filling conditions required for optimal aerodynamic performance and dose delivery. As anticipated, the total mass output and emitted dose delivered decreased as the dosing chamber diameter decreased. For a fixed dosing chamber diameter, the total mass output, of drug and excipient, decreased slightly as the fill flow rate was increased. However, the fine particle fraction and fine particle mass, of drug alone, followed an opposite trend, by increasing with an increase in fill flow rate. A decrease in dosing chamber diameter resulted in an increase in air velocity (higher Re) and a subsequent increase in packing density of the filled powders at a fixed flow rate. As the dosing chamber diameters decreased (at a given fill flow rate) the total mass output and fine particle mass decreased, however, an increase in fine particle fraction was observed. Dose reproducibility as indicated by standard deviations within f 10%, and a mean dose recovery of 95%+4%, indicated acceptable performance of the device. Future work will evaluate the relationship between particle size, powder flow, fill flow rate, fill density, and dose emission to optimize aerodynamic performance and dose delivery.     

Solid atomization technology and process of molten metal and alloy

A novel solid atomization technology has been developed with a high-velocity gas jet stream containing solid salt particles as the atomization medium. Metal and alloy powders with a finer particle size, a narrower size distribution and a higher cooling rate than those of the conventional gas atomization technology have been produced by this technology. The affecting factors of the particle size of as-prepared metallic powders have been analyzed, especially the influence of the state of NaCl particles.     

微粉化对三七质量影响的研究

为了比较三七普通粉和微粉的粉体学特征、水溶性浸出物含量、指标成分溶出量及溶出速度,探索三七粉碎的临界粒径,通过激光粒度分析仪和扫描电子显微镜对普通粉和微粉进行表征,测定粉体学参数休止角和堆密度,热浸法测定水溶性溶出物的含量,利用小杯溶出法进行指标成分的溶出实验,采用梯度HPLC分析人参皂苷Rg1、Rb1和三七皂苷R1的含量。结果表明:三七普通粉和微粉的粉体学特征、水溶性浸出物含量差异显著,人参皂苷Rg1、Rb1和三七皂苷R1的溶出速度微粉较快,但两者在溶出量上无显著差异。微粉化对中药的必要性应结合具体的中药进行研究,三七制备为100目的粉体在体外溶出已达到最适。