NANOCRYSTALLINE STRUCTURE AND INITIAL PERMEABILITY OF ANNEALED Fe_（73．5）Cu_1W_3Si_（13．5）B_9 Alloy

ＮＡＮＯＣＲＹＳＴＡＬＬＩＮＥＳＴＲＵＣＴＵＲＥＡＮＤＩＮＩＴＩＡＬＰＥＲＭＥＡＢＩＬＩＴＹＯＦＡＮＮＥＡＬＥＤＦｅ_（７３．５）Ｃｕ_１Ｗ_３Ｓｉ_（１３．５）Ｂ_９ＡｌｌｏｙＺＨＡＮＧＸｉａｎｇｙｉ,ＺＨＡＮＧＪｉｎｇｗｕａｎｄＺＨＥＮＧＹａｎｇｚｅ?..     

Defects producing formation of micro-cracks in aluminum during electrochemical charging with hydrogen

The main reason for the study of Fe-based (FINEMET and NANOPERM) alloys was their magnetic properties. The nanocrystalline phases -FeSi and -Fe are responsible for the soft magnetic properties of FINEMET and NANOPERM alloys, respectively. A new type of amorphous and nanocrystalline FeCo-based alloy (HITPERM) has recently been produced. Its soft magnetic properties, which are attributed to the formation of ′-FeCo phase during the crystallization process, persist to the –γ phase transformation at 980 °C. In spite of that the magnetic properties have got attention, the corrosion process on these amorphous and crystalline alloys became important due to the loss of magnetic properties. FINEMET alloys are more resistant to corrosion process than NANOPERM alloys in function of its Si content that acts on protector film formed during corrosion attack. The present work compares the magnetic flux density and the corrosion resistance in acid media of FINEMET, NANOPERM and HITPERM alloys, quantifies the losses on magnetic flux density due to corrosion process and introduces a new corrosion data about the amorphous and crystalline FeCoNbCuSiB alloy.     

Fe基非晶及纳米晶合金的制备和电化学腐蚀行为

分别采用单辊甩带法和非晶晶化退火法制备出非晶及纳米晶合金Fe73.5Si13.5B9Nb3Cu1;利用DSC、XRD和TEM对该非晶合金的晶化行为进行了分析;并用电化学极化曲线的方法和电化学阻抗技术研究了该非晶合金经不同温度退火后在1mol/LHCl溶液里的电化学腐蚀行为。结果表明,该非晶合金的晶化过程出现2个阶段。当退火温度为500℃时,合金尚未晶化,仍保持非晶态;当温度达到550℃时,出现了晶化衍射峰,晶粒平均直径约13nm;当温度达到600℃时,晶粒平均直径约为15nm。经过退火得到的纳米晶合金的腐蚀电位大于未退火的非晶,且阳极电流密度变得更低,表明纳米晶状态时的耐腐蚀性能比非晶状态的更好。该非晶合金未退火、550℃退火和600℃退火时的EIS均由单一容抗弧构成,具有一时间常数;且随着退火温度升高,电化学反应电荷转移电阻在增大。     

Eeffects Of Grain—Size Distribution On Effective Anisotropy And Coercivity For Nanocrystalline Hard Magnetic Material

以Nd2Fe14B为例，研究了单相纳米晶硬磁材料中有效各向异性和矫顽力随晶粒尺寸及其分布的变化关系．计算结果表明：材料的有效各向异性和矫顽力随晶粒尺寸减小而降低，当平均晶粒尺寸小于20nm时，其减小更为迅速；晶粒尺寸的非理想分布没有改变有效各向异性和矫顽力随晶粒尺寸的总体变化规律，但使材料有效各向异性和矫顽力进一步下降．当微结构因子pc取值为0．7时，计算结果与Manaf等人关于矫顽力的实验结果非常接近．纳米晶硬磁材料的矫顽力随晶粒尺寸下降主要是有效各向异性常数或各向异性场的减小引起的．     

Nanocrystalline τ2 phase obtained by mechanical alloying of Al60Fe15Si15Ti10 powder mixture followed by consolidation

In the present work an elemental powder mixture of Al60Fe15Si15Ti10 (at.%) was mechanically alloyed in a high-energy ball mill. A part of the milling product was examined in a calorimeter, while another portion was subjected to consolidation by hot-pressing at 1000 °C for 180 s under a pressure of 7.7 GPa. The results obtained show that a nanocrystalline cubic phase with the lattice parameter a₀ = 11.645 Å, isomorphous with the τ₂ (Al₂FeTi) phase, is formed during mechanical alloying process. Heating of the milling product in the calorimeter up to 720 °C causes limited growth of grains, however the τ₂ phase remains nanocrystalline with the mean crystallite size of 28 nm. Grain growth takes place during consolidation of the milling product as well, although the τ₂ phase remains nanocrystalline with the mean crystallite size of 34 nm. The microhardness of the bulk nanocrystalline sample is 1013 HV0.2 and its open porosity is 0.3%. The results obtained show that the quality of compaction with preserving nanometric grain size of the τ₂ phase is satisfactory and its microhardness is relatively high.     

纳米晶(Ag-Cu28)-25Sn合金粉末的制备及表征

采用机械合金化法制备纳米晶(Ag-Cu28)-25Sn合金粉末.用X射线衍射(XRD)仪、扫描电镜(SEM)、高分辨透射电镜(HRTEM)和差示扫描量热分析仪(DSC)等分析手段,对合金化过程中物相组成、微观结构及熔化特性进行表征.结果表明:(Ag-Cu28)-25Sn纳米晶合金粉末的物相组成为Cu3Sn和Ag4Sn.球磨 40 h,合金化完全,其熔化温度为548.5 ℃;球磨至60 h,合金明显非晶化,其熔化温度为554.0 ℃,熔程变小且在186.3和399.5 ℃处出现明显放热峰.HRTEM表明,纳米晶的尺寸约为5～10 nm,合金中有非晶态物质出现和晶格缺陷产生.200和400 ℃退火后,合金的平均晶粒尺寸分别为21.3和33.9 nm.     

FeCuMoSiB合金穆斯堡尔谱研究

用Ｘ射线衍射技术和穆斯堡尔谱技术，研究了Ｆｅ７３．５ＣｕＭｏ３Ｓｉ１３．５Ｂ９合金的结构和超业细相互作用。该合金的相组成为α－Ｆｅ（Ｓｉ）纳米晶和边界相即五余非晶相。典型纳米晶状态下的穆斯堡尔谱由５条亚谱构成，其中４条亚谱为６峰谱，对应α－Ｆｅ（Ｓｉ）相中的４种不同环境的Ｆｅ原子。另１条亚谱对应边界处的非晶相，研究了非晶带材经５００－６００℃不同温度晶化处理后的穆斯堡尔谱特性。     

Microstructure characteristics of as-surface nanocrystallized 1420 aluminum alloy by high-energy shot peening

A nanostructured surface layer was fabricated on 1420 aluminum alloy by high-energy shot peening.Microstructures were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM) and high-resolution electron microscope(HRTEM), and microhardness measurement was conducted along the depth from top surface layer to matrix of the sample peened for 30 rain. The results show that a nanocrystalline layer about 20μm in thickness is formed on the surface of the sample after high-energy shot peening, in which the grain size is changed from about 20 nm to 100 nm. In the surface layer of 20-50μm in depth, the microstructure consists of submicron grains. The surface nanocrystallization is accomplished by dislocation slip. The microhardness of the top surface nanostructured layer is enhanced obviously after high-energy shot peening(HESP) compared with that of the coarse-grained matrix.     

纳米晶软磁合金Fe_(73.5)Cu_1Nb_3Si_(13.5)B_9淬态脆化机制研究

本文采用正电子湮没、居里点与内耗等方法对纳米晶软磁合金Fe73 5 Cu1Nb3Si13 5 B9淬态脆化机制进行系统研究。研究结果表明FeCuNbSiB淬态脆化是由于发生结构弛豫造成 ,且其结构弛豫峰温度比常用Fe B Si非晶低得多 ,说明FeCuNbSiB比常用Fe B Si非晶易产生由结构弛豫造成的淬态脆化。     

Diffusion of chromium in nanocrystalline iron produced by means of surface mechanical attrition treatment

By means of surface mechanical attrition treatment (SMAT) to a pure iron plate, a nanometer-grained surface layer without porosity and contamination was fabricated. The average grain size in the top surface layer (of 5 μm thick) is about 10–25 nm, and the grain size stability can be maintained up to 653 K. Cr diffusion kinetics in the nanocrystalline Fe phase was measured by using second ion mass spectrometry within a temperature range of 573–653 K. Experimental results showed that diffusivity of Cr in the nanocrystalline Fe is 7–9 orders of magnitude higher than that in Fe lattice and 4–5 orders of magnitude higher than that in the grain boundaries (GBs) of α-Fe. The activation energy for Cr diffusion in the Fe nanophase is comparable to that of the GB diffusion, but the pre-exponential factor is much higher. The enhanced diffusivity of Cr may originate from a large volume fraction of non-equilibrium GBs and a considerable amount of triple junctions in the present nanocrystalline Fe sample processed by means of the SMAT technique.     

Synthesis and characterization of mechanically alloyed and shock-consolidated nanocrystalline NiAl intermetallic

The synthesis, microstructural characterization and microhardness of nanocrystalline B2-phase NiAl intermetallic are discussed in this paper. Nanophase NiAl powders were prepared by mechanical alloying of elemental Ni and Al powders under an argon atmosphere for different times (0–48 h). The alloyed nanocrystalline powders were then consolidated by shock compaction at a peak pressure of 4–6 GPa, to 83% dense compacts. Characterization by transmission electron microscopy (TEM) revealed that the microstructure of the shock-consolidated sample was retained at the nanoscale. The average crystallite size measurements revealed that mechanically alloyed NiAl grain size decreased from 48±27 to 9±3 nm with increasing mechanical alloying time from 8 to 48 h. The long-range-order parameters of powders mechanically alloyed for different times were determined, and were observed to vary between 0.82 for 5 h and 0.63 for 48 h of milling time. Following shock compaction, the long-range-order parameter was determined to be 0.76, 0.69 and 0.66, respectively, for the 16, 24 and 48 h alloyed specimens. Both the mechanically alloyed nanocrystalline NiAl powder and the shock-consolidated bulk specimen showed evidence of grain boundary dislocations, subgrains, and distorted regions. A large number of grain boundaries and defects were observed via high resolution TEM (HRTEM). Shear bands were also observed in the mechanically alloyed NiAl intermetallic powders and in the shock-consolidated compacts. Microhardness measurements of shock-consolidated material showed increasing microhardness with increasing crystallite size refinement, following Hall–Petch behavior.     

纳米晶Fe85Si1Al6Cr8扁平状颗粒材料微波吸收特性

摘要采用雾化工艺和高能球磨处理技术制备纳米晶Fe85Si1Al6Cr8扁平状颗粒合金粉，研究了高能球磨处理工艺对材料微结构、形貌和微波电磁特性的影响．结果表明，高能球磨处理使球形雾化粉粒形状扁平化并细化其晶粒，从而使Fe85Si1Al6Cr8微粉的微波磁导率显著提高，有效控制了介电常数．后续热处理可以进一步改善其微波电磁性能．对采用该材料制作的涂层吸波性能进行的测量结果表明，在频率为4GHz附近微波段具有良好的吸波性能．     

热膨胀方法研究Zr基块体非晶合金的晶化过程

利用电弧熔炼及铜模快速铸造法制备Zr41.2Ti13.8Cu12.5Ni10Be22.5块体非晶合金,通过热膨胀法测试晶化过程,与差示扫描量热法进行对比。通过高分辨电子显微镜观察晶化初期晶核的形成和长大规律。结果表明,热膨胀系数测试块体非晶合金的结构弛豫、玻璃转变、过冷液相区、晶化开始温度和晶化过程中不同晶化峰温度与差示扫描量热法测试结果完全吻合。在高分辨像中观察到近似球形的纳米晶粒和晶格条纹。然而,在高分辨像中很难辨认出晶化初期微小的晶化区域,只有对其进行快速傅里叶变换才能发现微小区域的晶化基本特征。     

Peculiarities of the R3(Fe,Si)29 phase formation in the Sm---Fe---Si system

The phase content of the Sm(Fe_1−xSi_x)_y alloys (0.05≤x≤0.15; 8.5≤y≤12) has been studied by X-ray diffraction using micromonocrystals. The compounds Sm₂(Fe,Si)₁₇, Sm(Fe,Si)₁₂ and a novel Sm₃(Fe,Si)₂₉ compound with a monoclinic unit cell are found. The lattice parameters of Sm₃(Fe,Si)₂₉ are: a=1.056 nm, b=0.850 nm, c=0.966 nm, β=96.8°. This compound forms as a result of a solid state transformation from the high-temperature Sm₂(Fe,Si)₁₇ phase. Diffuse effects observed in rocking photographs suggest transition structures arising from this transformation. The Curie temperatures of Sm₃(Fe,Si)₂₉ vary in the interval 496–521 K.     

纳米金刚石膜真空窗口的制备

使用自制的微波等离子体化学气相沉积装置,以乙醇为碳源在（100）硅表面制备了金刚石膜;然后用浓硝酸和氢氟酸的混合溶液腐蚀硅,制备出金刚石膜窗口。使用场发射扫描电镜（SEM）、X射线衍射、拉曼光谱（Raman）、原子力显微镜（AFM）表征和分析金刚石膜,并以自制的漏气率测量系统测量金刚石膜窗口的漏气率。结果表明:金刚石膜的厚度为15 μm,平均粗糙度值R_a为39.5 nm,晶粒的尺寸大小为30 nm,漏气率为8.8×10-9 Pa·m3/s。      

Mechanical properties in tension of mechanically attrited nanocrystalline iron by the use of the miniaturized disk bend test

The mechanical properties of warm compacted nanocrystalline (nc) iron powder compacts of near theoretical density in the grain size range between 8 and 33 nm were investigated. The elastic and plastic behavior were characterized by miniaturized disk bend tests and hardness measurements. Light and scanning electron microscopy (SEM) were used to document the deformation and fracture morphologies. The Young's modulus of the nc Fe was essentially the same as that of coarse grained Fe. All samples failed in a macroscopically brittle manner. Local plasticity in shear bands was observed in the samples with the larger grain sizes (>20 nm). An increasing failure stress with increasing grain size is probably due to a processing effect on the flaw controlled failure of the samples. The results are discussed in the context of the deformation and fracture behavior of micrometer grain size metals and alloys.     

Mechanical alloying of Mo—Si—Fe powders

Mechanical milling behavior of Mo-Si-Fe powders was investigated u sing XRD, SEM and TEM techniques. The mixtures of elemental molybdenum (>99%), s ilicon (>99%) and iron (>98%) powders with a stoichiometry of Mo5-xFe xSi3 (x=0.5, 1, 2) were milled in a planetary mill for up to 195 h. For all three powder mixt ures, high-energy milling of 60h led to formation of the Mo(Fe, Si) supers aturated solid solution (Moss); and to a remarkable expansion of the solub ility of Fe, Si in molybdenum. The transformation of Moss to an amorphous phase was identified after longer time milling. In the milling process, the grain size of Mo (Fe, Si) decreased gradually and the internal stress increased linearly. After 40 h milling, the grain size was reduced to about 11 nm. SEM analysis of milled powders showed that the particle size increased initially with milling time. After 195 h milling, particles exhibited a spherical morphology and the particle size were reduced to about 100 nm.     

Microstructure evolution and mechanical properties of nanocrystalline FeAl obtained by mechanical alloying and cold consolidation

In the present study high energy mechanical milling followed by cold temperature pressing consolidation has been used to obtain bulk nanocrystalline FeAl alloy. Fully dense disks with homogenous microstructure were obtained and bulk material show grain size of 40 nm. Thermal stability of the bulk material is studied by XRD and DSC techniques. Subsequent annealing at a temperature up to 480 °C for 2 h of the consolidated samples enabled supersaturated Fe(Al) solid solution to precipitate out fine metastable Al₅Fe₂, Al₁₃Fe₄ and Fe₃Al intermetallic phases. Low temperature annealing is responsible for the relaxation of the disordered structure by removing defects initially introduced by severe plastic deformation. Microhardness shows an increase with grain size reduction, as expected from Hall-Petch relationship at least down to a grain size of 74 nm, then a decrease at smallest grain sizes. This could be an indication of some softening for finest nanocrystallites. The peak hardening for the bulk nanocrystalline FeAl is detected after isochronal ageing at 480 °C.     

Fe73.5Cu1Mo3Si13.5B9超微晶磁粉芯的研究

本文对Ｆｅ７３．５Ｃｕ１ｍＯ３Ｓｉ１３．５Ｂ９超微晶合金带制作磁粉芯的工艺进行了研究。特别对粉的粒度，成形压力，绝缘的配比以及磁粉芯的磁性能进行了深入的探讨。发现磁粉芯的性能与制粉用的微晶带材是否具有优良磁性能无关。通过调整绝缘剂量及其组分可以使磁粉芯的磁性能发生相应的变化。超微晶粉的粒度对磁粉芯的性能及频率特性起着决定的作用。     

激光表面合金化原位制备Ti-Cu纳米晶金属间化合物涂层

利用激光表面合金化技术以铜粉为初始原料,在纯钛表面通过激光表面合金化原位反应成功制备了Ti-Cu纳米晶金属间化合物涂层。采用X-射线衍射仪(XRD)和高分辨透射电镜(HRTEM)分析了涂层的组成和组织结构,测试了涂层在不同载荷下的摩擦磨损性能。结果表明:通过激光表面合金化制备的涂层主要成分为Ti和金属间化合物TiCu、TiCu3、Ti3Cu相。涂层含有纳米晶Ti-Cu金属间化合物,晶粒尺寸为10~500nm。Ti-Cu金属间化合物涂层的摩擦因数随载荷增加而减小,体积磨损率在10-6~10-5 mm3/Nm数量级范围并随载荷的增加而增大,与纯钛底材相比,Ti-Cu金属间化合物涂层具有良好的耐磨性。