Al-Mg-Si-Cu合金中晶界和晶内析出相粗化规律的研究

采用显微硬度测试仪、扫描电镜和透射电镜观察及能谱分析,研究了Al-0.5Mg-1.0Si-0.8Cu(wt.%)合金的晶界析出规律和晶内析出相的粗化机制。结果表明:180℃时效处理的Al-0.5Mg-1.0Si-0.8Cu(wt.%)合金晶界处存在富Si相和Q相两类不连续分布的析出相,它们的尺寸分别约为1 mm和几十纳米;时效0.5 h时晶界处有少量富Si相,时效5 h时晶界富Si相明显增多,时效36 h时富Si相开始粗化且间距变大,再进一步时效其形貌和分布变化不大;晶界Q相与相邻晶粒铝基体的界面取向关系是:[510]Al//[1120]Q;时效36 h晶内开始出现粗化析出相,且随时效继续进行合金晶内析出大量粗化相,存在明显的晶界无析出带现象。晶内粗化析出相主要含有Si元素,呈片状、球状和棒状3种形貌。其中,棒状Si析出相是沿〈001〉Al方向生长的,且〈112〉Si//〈001〉Al,{111}Si//{010}Al。     

BT25y高温钛合金固溶处理及热暴露过程中硅化物的析出机制

TEM观察了BT25y高温钛合金硅化物在固溶处理以及热暴露过程中的析出行为,结合Calphad相图计算技术研究了该合金硅化物的析出机制。在经单相区990℃固溶处理后的个别样品和两相区940℃固溶处理后的部分样品中，观察到(Ti,Zr)5 Si3，硅化物颗粒，依据计算，分析这些硅化物可能是由于Si分布不均匀，局部浓度超过0．3％而析出的；在两相区940℃固溶处理后的样品中还观察到平衡析出的(Ti,Zr)6 Si3硅化物颗粒。两种固溶处理后的样品，在700℃热暴露过程中都有大量细颗粒(Ti,Zr)6 Si3硅化物弥散析出。     

Zr对Al—Si合金的变质作用

为了寻求铸造Al—Si合金的新型变质剂,我们对亚共晶Al—Si合金ZL101进行了大量加Zr变质试验。本文报导了加Zr变质处理的优点,如:Zr变质剂具有长效性,加入量范围宽,对壁厚不敏感,变质后合金具有较高的机械性能等。对Al—Si合金的Zr变质机理提出了初步看法。     

合金的玻璃形成能力对激光重熔Zr基非晶热影响区晶化的影响

通过脉冲激光重熔Zr55All 0Ni5Cu30非晶合金和Zr65Al7.5Ni10Cu17.5非晶合金,分析了具有不同玻璃形成能力的非晶合金热影响区晶化行为的差异。结果表明,玻璃形成能力稍差的Zr65Al7.5Ni10Cu17.5非晶合金比玻璃形成能力强的Zr55All 0Ni5Cu30非晶合金热影响区晶化严重。激光重熔Zr55Al10Ni5Cu30非晶合金4次后,热影响区仅有稀疏的球状晶粒析出;而激光重熔Zr65Al7.5Ni10Cu17.5非晶合金1次时,热影响区布满球状晶粒,激光重熔4次后,晶化晶粒长大明显,且在球状晶粒的内部呈现树枝状放射生长形态。激光重熔热影响区非晶合金的晶化行为与该合金的玻璃形成能力密切相关。玻璃形成能力越高,越有利于保持热影响区的非晶状态。     

Mg/Si含量比值对Al-Mg-Si合金析出行为的影响

采用显微硬度计、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)及能谱仪,研究了不同Mg/Si含量比的Al-Mg-Si合金在不同时效温度下的时效析出行为.合金为Mg含量相同,Mg/Si摩尔比接近2.0、1.0和0.5的三种A、B和C合金(合金总含量依次增多).结果表明:Mg/Si含量比对析出动力学有很大影响,温度越高Mg/Si摩尔比对时效动力学影响越大.SEM分析表明:Si含量越高的合金,晶界析出相越连续且尺寸越大,并有一定的晶界无析出带.HRTEM分析表明:过时效阶段,β′相的形成跟Mg/Si比和温度有关;两种时效温度下,在A合金中均析出β′相;而B和C合金在180℃时效主要析出β″相,250℃时效时,B合金中易形成TypeB相,C合金可析出TypeA、TypeB和TypeC三种相.     

镁合金表面宽带激光熔覆Cu-Zr-Al合金涂层

采用宽带激光熔覆技术在镁合金表面制备了Cu-Zr-Al合金涂层。研究结果表明,Cu-Zr-Al合金涂层是由ZrCu、Cu8Zr3、Cu1 0Zr7和Cu5 1Zr1 4金属间化合物和α-Mg所构成,其中ZrCu相呈连续网状分布于由Cu8Zr3、Cu1 0Zr7、Cu5 1Zr1 4相所构成的灰色区周围。熔覆区和热影响区之间呈现出犬牙交错型界面结合特征。受熔覆材料元素扩散迁移的影响,热影响区具有典型的共晶组织形态。由于合金涂层中多种金属间化合物的增强作用,使合金涂层具有高的硬度、弹性模量、耐磨性和耐蚀性。     

激光熔覆制备Al-Si-Cu-Fe准晶态合金涂层的研究

本文报道了在氮气气氛下 ,利用激光熔覆Al50 Si15Cu2 0 Fe15准晶粉末制备Al Si Cu Fe准晶态合金涂层。通过选取适当的激光熔覆参数 ,成功的制备了Al Si Cu Fe准晶态合金涂层。X射线衍射 (XRD)分析显示涂层中含有 1/ 1立方类似相α- (Al,Si)CuFe、β -Al(Si)Fe(Cu)相、λ -Al13 Fe4相和Al0 .7Fe3 Si0 .3 相。制备的涂层显微硬度达Hv914 ,α相和 β相中高的Si元素含量和类似相λ -Al13 Fe4的高含量是影响Al Si Cu Fe合金涂层硬度的主要因素。光学显微镜下显示Al Si Cu Fe合金涂层枝晶细密且取向比较一致 ,一次枝晶臂间距约为 2 5 μm ,且有明显的二次枝晶存在 ,二次枝晶臂间距约为 8μm。摩擦学试验显示 ,随着滑动速度的增加 ,涂层与对偶球之间的摩擦系数逐渐降低 ,且趋于稳定。     

Cu-Ni-Cr合金调幅组织的高指数明场欠焦象研究

用欠焦高指数衍射明场成像法显示时效初期的第二相粒子,已在Ni—38Cu—6 Si(at％)合金调幅组织研究中获得了证实。对于有些合金分解的第二相既非有序结构又无可与基体衍射斑点相区分的反射,故不能有效地采用暗场像,则欠焦高指数明场像具有独到的作用。     

Fe_(81)Zr_7Nb_2B_(10)和Fe_(78)Co_(2.5)Zr_7Nb_2B_(10)Cu_(0.5)合金的热性能、微观结构及磁性能研究

采用单辊快淬法制备了Fe81Zr7Nb2B10和Fe78Co2.5Zr7Nb2B10Cu0.5非晶合金,在不同温度下对两种合金进行了热处理。利用差热分析仪(DTA)、X射线衍射仪(XRD)和振动样品磁强计(VSM)等仪器对两种合金的热性能、微观结构和磁性能进行了测试分析。结果表明在Fe78Co2.5Zr7Nb2B10Cu0.5合金的晶化过程中存在预结晶效应,而在Fe81Zr7Nb2B10合金的晶化过程中没有。Fe81Zr7Nb2B10和Fe78Co2.5Zr7Nb2B10Cu0.5合金经803 K退火后,分别有α-Fe和α-Fe(Co)相从非晶基体中析出。随退火温度的升高,两种合金的比饱和磁化强度(Ms)变化趋势相似,但矫顽力(Hc)变化趋势明显不同。     

Fe81Zr7Nb2B10和Fe78Co2.5Zr7Nb2B10Cu0.5合金的热性能、微观结构及磁性能研究

采用单辊快淬法制备了Fe81Zr7Nb2B10和Fe78Co2.5Zr7Nb2B10Cu0.5非晶合金,在不同温度下对两种合金进行了热处理。利用差热分析仪(DTA)、X射线衍射仪(XRD)和振动样品磁强计(VSM)等仪器对两种合金的热性能、微观结构和磁性能进行了测试分析。结果表明在Fe78Co2.5Zr7Nb2B10Cu0.5合金的晶化过程中存在预结晶效应,而在Fe81Zr7Nb2B10合金的晶化过程中没有。Fe81Zr7Nb2B10和Fe78Co2.5Zr7Nb2B10Cu0.5合金经803 K退火后,分别有α-Fe和α-Fe(Co)相从非晶基体中析出。随退火温度的升高,两种合金的比饱和磁化强度(Ms)变化趋势相似,但矫顽力(Hc)变化趋势明显不同。     

Evidence for Glass–glass Interfaces in a Columnar Cu–Zr Nanoglass

Comprehensive analyses of the atomic structure using advanced analytical transmission electron microscopy-based methods combined with atom probe tomography confirm the presence of distinct glass–glass interfaces in a columnar Cu-Zr nanoglass synthesized by magnetron sputtering. These analyses provide first-time in-depth characterization of sputtered film nanoglasses and indicate that glass–glass interfaces indeed present an amorphous phase with reduced mass density as compared to the neighboring amorphous regions. Moreover, dedicated analyses of the diffusion kinetics by time-of-flight secondary ion mass spectroscopy (ToF SIMS) prove significantly enhanced diffusivity, suggesting fast transport along the low density glass–glass interfaces. The present results further indicate that sputter deposition is a feasible technique for reliable production of nanoglasses and that some of the concepts proposed for this new class of glassy materials are applicable.     

无团聚纳米级SnO_2粉末及其气敏元件的制备

用液相沉淀法在结晶五水四氯化锡的水溶液中滴加浓氨水，通过在沉淀时加入高分子有机分散剂，剧烈搅拌，控制反应结束时ｐＨ值，用无水乙醇洗涤、冷冻干燥及选取适当的煅烧温度等一系列工艺手段来制取ＳｎＯ２粉末。将得到的粉末用ＴＥＭ、ＢＥＴ及ＸＲＤ半峰宽法测定其粒径大小，证明粉末最小平均粒径可至３．７９ｎｍ且无团聚存在，ＸＲＤ分析表明所得的ＳｎＯ２为四方相。将此粉末制成气敏元件，经测试表明气敏性能有很大提高。     

不同类型降水对毫米波传播特性的影响研究

为了提高复杂降水条件下毫米波传播衰减的评估精度,通过分析多个地区的降水谱特征,得出具有代表性的层状云降雨、积层混合云降雨、积雨云降雨以及干雪、湿雪的谱分布参数,然后结合降水粒子的形状、相态、介电模型,计算降水体目标在毫米波波段的散射特性.结果表明,降水强度不是唯一影响毫米波传播衰减的因素; 降水粒子相态、谱分布、入射波频率和温度等对毫米波传播特性均有不同程度的影响,其中谱分布和数密度是影响降雨对毫米波衰减的主要因素; 冰水构成比例是影响降雪对毫米波衰减的主要因素; 不同相态的降水,尤其是干雪、湿雪和雨对毫米波传播影响的差异较大; 而温度的影响较小.并建立了考虑谱分布和温度的降水衰减模型.     

Kinetics of structural and phase transformations in thin SiO<Subscript>x</Subscript> films in the course of a rapid thermal annealing

Infrared spectroscopy and analysis of photoluminescence spectra have been used to study variations in the composition of the oxide phase in a SiO_x film and the precipitation of the Si phase in the course of a rapid thermal annealing for 1–40 s at temperatures of 500–1000°C. Kinetics of phase segregation has been observed for the first time at temperatures of 600–700°C: an increase in the amount of precipitated silicon as the annealing duration increases followed by an eventual leveling off. The phase separation is brought to completion in a time as short as 1 s at temperatures higher than 900°C. The diffusion coefficient is estimated in the context of a model of the diffusion-controlled formation of Si nanoparticles. The obtained values of the diffusion coefficient exceed, by five to ten orders of magnitude, those of the silicon diffusion coefficients in SiO₂ and Si and are comparable to the diffusion coefficients of the oxygen contained in these structures. It is assumed that oxygen mobility forms the basis for the mechanism of structural and phase transformations in the SiO_x layers and for the formation of Si nanoparticles in the course of annealing.     

Constrained iterative technique with embedded neural network for dual-polarization radar correction of rain path attenuation

A new stable backward iterative technique to correct for path attenuation and differential attenuation is presented here. The technique named, neural network iterative polarimetric precipitation estimator by radar (NIPPER), is based on a polarimetric model used to train an embedded neural network, constrained by the measurement of the differential phase along the rain path. Simulations are used to investigate the efficiency, accuracy, and the robustness of the proposed technique. The precipitation is characterized with respect to raindrop size, shape, and orientation distribution. The performance of NIPPER is evaluated by using simulated radar volumes scan generated from S-band radar measurements. A sensitivity analysis is performed in order to evaluate the expected errors of NIPPER. These evaluations show relatively better performance and robustness of the attenuation correction process when compared with currently available techniques.     

Thermochemistry of alloys of transition metals: Part III. Copper-silver, -titanium, -zirconium,and -hafnium at 1373 K

The enthalpies of mixing of liquid copper with liquid silver and with solid titanium, zirconium, and hafnium have been measured by high temperature reaction calorimetry at 1371 to 1373 K. A least squares treatment of the data for copper-silver alloys yields the following expression for the molar enthalpy of mixing: δH_mix = x_Agx_Cu(17.66-5.46 x_Ag) kJ mol^-1. The enthalpies of solution of solid titanium, zirconium, and hafnium in dilute solutions in liquid copper are all exothermic; the following values were found: -2.0 kJ mol^-1 for Ti, -52.5 kJ mol^-1 for Zr, and -46.3 kJ mol^-1 for Hf. These values are all significantly less exothermic than predicted by the semiempirical theory of Miedema. The enthalpies of formation of congruent melting intermetallic phases in the systems Cu-Ti, Cu-Zr, and Cu-Hf were measured by drop calorimetry or by solution calorimetry in liquid copper. The enthalpies of formation of the solid alloys have been compared with corresponding data for the liquid alloys.     

纳米钛酸锶粉体的特殊液相沉淀法制备

以制备纳米钛酸锶粉体为目标,在液相反应胶粒析出机理分析的基础上,通过碳酸铵沉淀途径,采用特殊的快速高强度机械混合液相沉淀法,调控各种工艺条件,例如浓度、pH值、高机械混合强度以及陈化时间等,得到分散性和过滤性均好的碳酸锶和无定形氢氧化氧钛高度混合的纳米粉体前驱体,其粒径为3～4nm(平均3.5nm)。经920℃度焙烧,获得了结晶度好、分散性好、平均粒径56nm的立方相钛酸锶粉体。     

降水对Ku/Ka频段星地链路衰减特性的影响研究

近年来,Ku和Ka卫星在广播、通信和军事等领域应用数量越来越多,传统的Ku和Ka波段星地链路降水衰减预报模型基于经验关系和理想假设,考虑降水微物理特性不足,针对此问题,在实测降水粒子微物理特征的基础上定量分析了降水垂直分布、粒子形状、粒子取向、粒子相态等对Ku和Ka频段信号衰减的影响特性.结果表明,与考虑降水非均匀垂直分布的计算结果相比,ITU和SAM模型是基于降水分布均匀的假设,无法代表降水垂直分布不均匀时的衰减情况;降水粒子形状和取向对衰减的影响较小,在13GHz和32GHz频段,球形和非球形粒子衰减值的平均绝对偏差均在0.01dB以下,不同粒子取向时衰减系数的平均绝对偏差最大值为0.00098dB/km和0.0207dB/km;不同相态的降水引起的衰减差异较大,衰减值从大到小依次是湿雪、水和冰.研究结果可以为Ku和Ka波段星地链路传播特性评估及降雨反演新方法提供基本的理论支撑和数据参考.     

Polarimetric radar modeling of mixtures of precipitation particles

With the advances of dual-polarized radar techniques in meteorology it is now possible to deduce precipitation microphysical characteristics in far more detail than possible with reflectivity measurements alone. Radar parameters such as differential reflectivity and differential phase between horizontal and vertical polarizations have been studied in detail as well as linear depolarization ratio, copolar correlation coefficient, and backscatter differential phase. While these parameters can be linked to certain microphysical properties of specific classes of precipitation such as raindrops or hail, very little study has been directed at the practically important cases of mixtures of different types of precipitation particles such as rain, hail, graupel, ice crystals, and snow. Each type can have different size, shape, orientation, and dielectric constant distributions. The present treatment is rigorous and is based on the Mueller matrix formulation. Radar parameters are derived from the averaged Mueller matrix computations. Careful consideration is given to the orientation and size distributions of the different particle types. After calculating single particle scattering characteristics, some simple two-component mixtures such as rain/hail and ice crystals/snow are considered. Finally, a 2D numerical cloud model is used to simulate the rain, hail/graupel, and snow fields of an evolving convective storm from which the radar parameters are derived for the initial, peak, and dissipating stages of the storm. Model computations are performed at C and S-band frequencies     

沉积静电效应及防护研究

简述沉积静电的形成机理，介绍了沉积静电的3种放电形式：跳火花和电弧、表面流光放电、电晕放电；讨论了沉积静电的放电效应；通过对无沉积、轻度沉积、严重沉积3种静电条件下电磁场天线接收信号的分析，研究了沉积静电对导航系统的影响；针对沉积静电的危害，从沉积静电防护的目标和防护措施两方面讨论了沉积静电的防护对策。