新型镍基粉末高温合金的高温变形行为

采用Gleeble-1500热模拟机对新型第三代镍基粉末高温合金FGH98Ⅰ在不同变形温度(950~1150℃)及不同变形速率(0.0003~1s-1)下高温变形行为进行了研究,绘制了动态RTT曲线,并建立了合金的热变形本构关系。结果表明:合金的流变应力随变形温度的升高和应变速率的降低而降低,当变形温度≤1100℃、应变速率≥0.0003s-1时,其流变应力随应变量增加呈动态再结晶特征;在应变速率≤0.01s-1的高温变形条件下,其动态再结晶的开始时间与变形温度无线性关系;实验验证了采用考虑应变量的双曲正弦模型能较好地反映合金在热变形过程中流变应力的变化规律。     

Al-17.5Si-4Cu-0.5Mg合金热变形行为及其加工图

采用Gleebe-1500D热压缩模拟试验机在变形温度350~500℃、应变速率0.001~5s-1的条件下对Al-17.5Si-4Cu-0.5Mg合金进行热压缩实验,研究该合金在热塑性变形下的流变应力行为及其热加工特性,研究结果表明:Al-17.5Si-4Cu-0.5Mg合金为正应变速率敏感材料;该合金可用Znenr-Hollomon参数双曲正弦形式来描述高温塑性变形时的流变应力行为;合金平均热变形激活能Q为308.61k J/mol。基于动态材料模型(DMM)建立了Al-17.5Si-4Cu-0.5Mg合金的热加工图,并结合热加工图和显微组织分析获得了该合金较优的热变形工艺参数:变形温度为400~470℃,应变速率为0.1s-1。     

挤压态喷射成形GH738合金热变形行为及组织研究

在温度950~1150℃、应变速率0.001~1 s–1及工程应变50%条件下,利用Gleeble-3500TM热模拟试验机对挤压态喷射成形GH738合金进行热压缩实验,研究合金的流变应力,建立合金热变形本构关系,利用EBSD分析合金组织演变。结果表明:合金流变应力随温度的升高和应变速率的减小而降低,在相同变形条件下,具有细晶组织特征的挤压态喷射成形GH738合金峰值流变应力低于粗晶组织的铸锻GH738合金;挤压态喷射成形GH738合金热变形激活能为651.08 kJ·mol–1,GH738合金的热变形激活能随着初始平均晶粒尺寸的减小而升高;形变温度的升高使挤压态喷射成形GH738合金初始被拉长的晶粒逐渐演变为等轴再结晶晶粒,在1000℃以上获得完全动态再结晶组织,再结晶组织随形变温度的进一步升高发生长大。     

阻燃钛合金高温变形行为研究

通过等温恒应变速率热模拟压缩试验,研究了一种铸态组织的阻燃钛合金在变形温度900~1200℃,应变速率0.001～1s-1下的高温流变应力和组织演变,计算了变形激活能及应力指数,并给出了该合金变形的本构方程.结果表明,此种阻燃钛合金高温变形是扩散控制的过程,软化机制以动态回复为主,但在应变速率较高时会发生项链状动态再结晶,而在应变速率较低时会发生连续再结晶,合金中的碳化物形貌在高温变形过程中也会发生转变.     

7150铝合金热变形行为及微观组织

采用Gleeble热模拟机进行热压缩实验,研究7150铝合金在变形温度为300~450℃、应变速率为0.01~10s-1条件下的变形行为,采用Zener-Hollomon参数法构建合金高温塑性变形本构方程,并对变形后的微观组织进行分析。研究表明:7150铝合金的流变应力随应变速率增大而增大,随变形温度增大而降低。该合金热压缩变形的流变应力行为可用双曲正弦形式的本构方程描述,其参数A为4.161×1014s-1,α为0.01956 MPa-1,n为5.14336,热变形激活能Q为229.7531k J/mol。随着温度升高和应变速率降低,动态再结晶逐渐取代动态回复成为合金的主要软化机制。     

7050高强度铝合金流变行为研究

通过等温压缩试验研究了7050铝合金在变形温度300~450℃、应变速率0.01 s-1~10s-1条件下的流变应力变化规律,计算并建立了描述7050铝合金高温变形特性的本构方程.结果表明:变形温度和应变速率对7050铝合金流变应力影响显著,随变形温度升高和变形速率的降低,相同变形程度下合金的流变应力显著降低,并且在较低的应变下合金即可达到稳态流变状态.经计算,在本试验条件下,7050铝合金的热变形激活能为151.63 kJ/mol.     

TA7钛合金高温流变行为研究

通过热压缩试验研究了TA7钛合金在变形温度850~1000℃、应变速率0.001~0.1s-1条件下的流变应力变化规律,计算并建立了描述TA7钛合金高温变形特性的本构方程。结果表明:变形温度和应变速率对TA7钛合金流变应力影响显著,随变形温度升高和变形速率的降低,相同变形程度下合金的流变应力显著降低,并且在较低的应变下合金即可达到稳态流变状态。     

新型超高强Al-Zn-Mg-Cu铝合金热压缩变形的流变应力行为

采用热力模拟试验方法进行热压缩变形试验,研究了一种新型Al-Zn-Mg-Cu合金在变形温度为300～450℃,应变速率为0.001～1s-1,压缩变形程度为50%条件下的流变应力行为.结果表明,变形温度和应变速率对合金流变应力的大小影响显著,流变应力随变形温度的升高而降低,随应变速率的提高而增大.采用统计回归方法建立了...     

粉末冶金TiAl合金的热变形行为研究

在Gleeble-3500热模拟试验机上对粉末冶金TiAl合金进行热压缩试验,变形温度为1050~1200℃,,应变率0.001~0.1 s-1,工程应变量为50%,研究其在高温压缩变形中的流变应力行为。研究结果表明:在实验范围内,粉末冶金TiAl合金在热压缩变形过程中发生了明显的动态再结晶,其流变应力随应变速率的增大而增大,随变形温度的升高而降低;粉末冶金TiAl合金热压缩变形过程的流变行为可用包含Arrhenius项的Zener-Hollomon参数来描述,所获得的峰值应力表达式为:σ=90.91ln{(Z/1.68×1016)1/2.06+[(Z/1.68×1016)2/2.06+1]1/2},其变形激活能为477.56kJ/mol,经验算该方程可以较好地描述该合金的变形特点。     

热变形条件对含银Al-Cu-Mg耐热铝合金流变应力和组织的影响

采用热模拟试验对一种含银Al-Cu-Mg耐热铝合金进行热压缩试验,研究了合金在热压缩变形温度和应变速率分别为340～500℃,0.001～10s-1的条件下的流变应力行为和变形组织.结果表明:合金的流变应力随应变速率的增大而增大,随变形温度的升高而减小.该合金热压缩变形的流变应力行为可用双曲正弦形式的本构方程来描述,也可用Zener-Hollomon参数来描述,其变形激活能为196.27kJ/mol.在较低的变形温度或较高的应变速率下,合金组织中主要存在沿垂直于压缩方向拉长了的晶粒.随着变形温度的升高或应变速率的降低,拉长的晶粒发生粗化,并且合金中出现了再结晶晶粒,说明合金中的主要软化机制逐步由动态回复转变为动态再结晶.该合金较适宜的热轧温度为380～460℃,应变速率为0.1～10s-1.     

ICP-AES法测定纯铜中的Bi,Sb,As,Fe,Ni,Pb,Sn,Zn,Ag的方法

研究了ICP-AES法测定纯铜中的Bi,Sb,As,Fe,Ni,Pb,Sn,Zn和Ag等9个元素的分析方法.进行了基体元素铜对9个分析元素的光谱干扰研究,选择了合适的分析谱线,同时测定了分析方法的检出限.     

Triton, Pluto, Centaurs, and Trans-Neptunian Bodies

The diverse populations of icy bodies of the outer Solar System (OSS) give critical information on the composition and structure of the solar nebula and the early phases of planet formation. The two principal repositories of icy bodies are the Kuiper belt or disk, and the Oort Cloud, both of which are the source regions of the comets. Nearly 1000 individual Kuiper belt objects have been discovered; their dynamical distribution is a clue to the early outward migration and gravitational scattering power of Neptune. Pluto is perhaps the largest Kuiper belt object. Pluto is distinguished by its large satellite, a variable atmosphere, and a surface composed of several ices and probable organic solid materials that give it color. Triton is probably a former member of the Kuiper belt population, suggested by its retrograde orbit as a satellite of Neptune. Like Pluto, Triton has a variable atmosphere, compositionally diverse icy surface, and an organic atmospheric haze. Centaur objects appear to come from the Kuiper belt and occupy temporary orbits in the planetary zone; the compositional similarity of one well studied Centaur (5145 Pholus) to comets is notable. New discoveries continue apace, as observational surveys reveal new objects and refined observing techniques yield more physical information about specific bodies.     

A survey of the outer planets Jupiter,Saturn, Uranus,Neptune, Pluto,and their satellites

A survey of current knowledge about Jupiter, Saturn, Uranus, Neptune, Pluto, and their satellites is presented. The best available numerical values are given for physical parameters, including orbital and body properties, atmospheric composition and structure, and photometric parameters. The more acceptable current theories of these bodies are outlined with thorough referencing offering access to the details. The survey attempts to cover the literature through May 1, 1972. Prepared Under Contract No. NAS7-100 National Aeronautics and Space Administration.     

Ion engine grids: Function,main parameters,issues, configurations,geometries, materials and fabrication methods

Ion optics are crucial components of ion thrusters and the study of the different ion extraction solutions used since the beginning of the electric propulsion era is essential to understand the evolution of ion engines. This work describes ion engine grids' main functions, parameters and issues related to thermal expansion and sputter erosion, and then introduces a review of ion optics used for significant launched and tested ion thrusters since 1970. Configurations, geometries, materials and fabrication methods are analyzed to understand when typical ion thrusters use two or three grids, what are the thicknesses and aperture sizes of the screen, accelerator and decelerator grids, why molybdenum and carbon-based materials such as pyrolytic graphite and carbon–carbon are the best available options for ion optics and what is the manufacturing method for each material.     

加快维修周转时间

大到整个飞机机身,小到某个飞机附件,周转时间都是十分重要的。在成本、质量和速度的三角关系中,后者正在占据越来越重要的地位。现在航空业出现一种新趋势,即航空公司在寻找维修公司时更注重维修周转时间的长短,以前,却是更为注重维修价格的高低。随着飞机营运费用的升高,周转     

组织、加工、实施

瑞士威力铭-马科黛尔公司在欧洲机床展(EMO)上展示了带直接驱动技术的超精密棒料铣车复合加工中心。威力铭公司是全球第一家制造铣/钻与车棒料复合加工中心的厂家。公司首次推出超精密的"多工序加工中心",即直线轴和旋转轴全部被直接驱动,在数控系统中输入     

维修数据传输:更快速、更廉价、更好

一直以来,航空公司大多采用ACARS通信系统(飞机通信寻址和报告系统)进行空中通信服务.但与陆地通信系统相比,该系统的传输速度慢而且成本高,成为目前影响飞行数据传输速度的重要因素之一.一些MRO软件供应商已开始开发机载无线通信系统,试图改善以往缓慢、昂贵和复杂的空中无线服务,使飞行中生成的重要维修数据以更低的成本、更快的速度和更高效率实现传输.     

CIR Morphology, Turbulence, Discontinuities, and Energetic Particles

Corotating interaction regions (CIRs) in the middle heliosphere have distinct morphological features and associated patterns of turbulence and energetic particles. This report summarizes current understanding of those features and patterns, discusses how they can vary from case to case and with distance from the Sun and possible causes of those variations, presents an analytical model of the morphological features found in earlier qualitative models and numerical simulations, and identifies aspects of the features and patterns that have yet to be resolved. This revised version was published online in August 2006 with corrections to the Cover Date.