采用核磁共振研究FeNbB纳米晶合金中的93Nb

FeMB (M =Zr、Ti、Ta、Mo和Nb)三元系铁基纳米晶合金具有优异的磁性能(饱和磁化强度比传统FINEMET合金的高 ) ,引起人们极大的兴趣。在这些三元系中 ,FeNbB合金表现出不同的结晶过程 ,且具有最小晶粒尺寸的纳米结构。巴西、法国和斯洛伐克的学者采用核磁共振 (NMR)技术研究了退火过程中Fe80 5Nb7B1 2 5快淬带的结构和磁性能变化。采用熔体快淬法制备了平均横截面积为10 μm× 2 8μm的Fe80 5Nb7B1 2 5非晶带。在高真空炉中将快淬带片分别于 5 10℃和6 10℃退火 1h获得纳米晶材料。X射线衍射和透射电镜观察表明 ,5 10℃…     

MA法制备Fe83Nb7B9Cu1纳米晶粉末及其热稳定性

利用高能球磨法在Fe Nb B Cu体系中获得纳米晶粉末 ,研究了机械球磨过程中产物的组织结构、α Fe相平均晶粒尺寸及其热稳定性。结果表明 :采用Fe 2 0B中间合金粉末代替B粉并未明显影响机械合金化动力学过程 ;球磨至 5h时 ,即可获得平均晶粒尺寸约 18nm的α Fe单相过饱和固溶体 ,其后延长球磨时间 ,晶粒尺寸缓慢减小 ,至 45h后 ,平均晶粒尺寸减小到 9nm。退火处理后的XRD分析表明 ,α Fe过饱和固溶体从 10 0℃开始发生结构弛豫现象 ,738.8℃后则发生了相转变 :α Fe过饱和固溶体→α Fe固溶体 Fe3 B FeB ,在 5 5 0℃以内退火 ,纳米晶粒长大不明显 ,在 770～ 95 0℃范围内退火 ,晶粒开始明显长大 ,但晶粒尺寸仍处于纳米级范围。     

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。     

Fe-Nd-Al系非晶合金条带样品的磁性机理研究

摘 要: 对Fe53Nd37Al10合金甩带速度为40 m/s和20 m/s条带样品的磁性能、磁粘滞行为和微观结构进行研究,分析了该合金条带的矫顽力机理。结果表明：Fe53Nd37Al10合金甩带速度为40 m/s和20 m/s条带样品的剩余磁化强度Mr分别为33.50 Am2/kg和36 .05 Am2/kg,矫顽力iHc为62.00 kA/m 和121.50 kA/m。40 m/s条带样品的热涨落场Hf,激活体积Va和激活直径Da分别为2.47 mT,3.90×10-18 cm3和19.53 nm;而20 m/s条带样品为2.73 mT,3.53×10-18 cm3和18.89 nm。40 m/s条带样品里面存在直径小于5 nm的纳米团簇,而20 m/s条带样品的纳米团簇直径为5-10 nm,且纳米团簇数量更多。Fe-Nd-Al非晶条带里面同时存在交换耦合和钉扎两种作用,纳米团簇的尺寸和数量,以及多个团簇组成的作用单元是影响非晶条带矫顽力的主要原因。     

高压下Fe84Nb4W3B9纳米晶软磁块体合金的制备

采用机械合金化(MA)法和低温高压快速烧结工艺制备了Fe84Nb4W3B9软磁合金粉末及其块体合金,并研究了粉末的晶粒尺寸、热稳定性和块体合金的相组成,晶粒大小以及相对密度与烧结条件的关系.结果表明(1)MA60h后,可获得单相α-Fe纳米晶(8.6nm)过饱和固溶体粉末(2)在MA粉末DSC升温曲线中,分别出现3个强弱不一的放热峰,依次发生了畸变的纳米晶过饱和固溶体的结构弛豫、纳米晶粒长大以及固溶体的相分解过程;(3)在P=5.5GPa,t=3min的烧结条件下,当Pw≥980W后,可获得相对密度98.2%以上、单相α-Fe纳米晶(20.3nm)块体合金,其磁性能为比饱和磁化强度Ms=154.0emu·g-1,矫顽力Hc=7.474×103A·m-1.     

IrMn顶钉扎自旋阀中Ta缓冲层的优化研究

通过直流磁控溅射法在硅 /二氧化硅基底上沉积了Ta膜 ,Ta/NiFe双层膜和IrMn顶钉扎自旋阀薄膜 ,研究了Ta、Ta/NiFe膜的晶格结构和表面情况 ,及自旋阀的磁性能 ,结果表明 ,自旋阀的磁电阻率、矫顽力和交换场等性能与Ta缓冲层厚度有密切的关系 ,在Ta缓冲层为 3nm时自旋阀的磁电阻率 (9 2 4 % )和交换场 (2 5 5× (10 3 / 4π)A/m)达到最大值 ,而矫顽力 (2 4 3× (10 3 / 4π)A/m)比较小     

Nb、Si、B含量的联动调整对Finemet型薄带结构及性能的影响

本文用V部分替代Nb并适当调整Si与B的含量,通过单辊快淬技术及退火工艺制备了原始成分为Fe73Si15Nb3B8Cu1和优化成分为Fe73Si15.5Nb1.1V2.4B7Cu1的Finemet型非晶纳米晶薄带。利用X射线衍射仪、透射电子显微镜、磁性能测试仪研究了薄带的结构及磁性能。结果表明：两种快淬态薄带主要为非晶结构,合金具有良好的非晶形成能力;采用Luborsky法评价薄带韧性,发现含V的快淬态薄带的断裂应变λt为5.05×10-2,其韧性较差;两种退火态薄带中的纳米晶晶粒大小分别约为14.8 nm与13.2 nm;与原始成分薄带相比,含V薄带的居里温度Tc,晶化起始温度Tx1有少量降低;含V薄带的饱和磁化强度略低于原始薄带,但是其矫顽力较小,其环形磁芯样品静态初始磁导率为1.269×105、静态损耗为1.748 J/m3,动态测试显示,随着频率的增加,含V薄带损耗较原始薄带小的优势更加明显。     

纳米复合材料及应用

由超急冷 (冷速 >10 4 K/s)合金液体凝固得到的Fe、Co、Ni、Al、Mg、Ti基非晶态合金经过加热时效处理后在非晶相中形成了均匀分布的纳米晶粒子 ,粒径约几十纳米 ,这样就得到了纳米复合材料。此外也可采用将非晶粉末加热挤压来获取纳米复合材料 ,目前开发出的主要纳米复合材料如下表所列 :合金成分组织 Bs/TBr/T Hc/A·m- 1 μe( 1kHz) (BH) max/kJ·m- 3Fe M B(M =Zr、Hf、Nb)软磁合金非晶相围着均匀分布的10～ 2 0nm的α Fe相 1 5～ 1 7 5～ 83～ 7× 10 4Fe Pt B硬磁合金 非晶相 +析出的L10 -FePt纳米晶相 0 9～ 1 0 3 0 0…     

立体仿形铣床床身浇注系统设计

1　铸件结构及要求XB4 4 2 0 0半自动立体仿形铣床床身 (见图 1)材质为 HT30 0 ,质量 15 .3t,最大轮廓尺寸为 7340× 15 5 0× 5 80 (mm ) ,主要壁厚 5 3m m,最大 10 9mm,最小 2 0m m,两导轨面处的尺寸为 70 30× 6 70× 5 3(mm)和70 30× 380× 5 3(mm)。除铸件内腔、部分端面、侧面、底面为毛面 ,其余均为加工面。要求粗加工后进行时效处理 ,导轨面硬度不得低于 175 HB,各处硬度差不得超出 2 5 HB;铸件不应有降低结构强度、影响切削加工和工业造型的铸造缺陷 ;导轨面不允许存在深度超过实际加工余量的铸造缺陷 ;铸件主要尺寸精度不低…     

双相软磁合金晶间非晶相Curie温度的增强效应

控制退火处理工艺使Fe73．5Cu1Nb3Si13．5B9非晶合金发生纳米晶化，获得不同晶粒尺度和晶相体积分数的非晶纳米晶双相组织状态．基于铁磁学严格Heisenberg自旋交换模型，构造适合非晶纳米晶双相结构要求的双相自旋团聚点阵．采用Monte Carlo模拟方法对上述双相自旋交换耦合点阵进行数值模拟计算．实验测定了经不同退火处理后双相Fe73．5Cu1Nb3Si13．5B9合金的纳米晶粒大小、纳米晶相所占体积分数以及晶间非晶相厚度对晶间非晶相Curie温度的影响．发现晶间非晶相Curie温度与其厚度的倒数成线性关系．模拟计算与实验测量结果相符．     

Fe表面多种离子注入层的研究SCIEI

本文应用Auger电子能谱及透射电镜研究了纯Fe表面分别注入Ni^+,Mo^+,B^+等单种离子及组合注入3种离子所引起的表面层化学成分分布及微观结构的变化。离子能量50—150keV,剂量5×10^(15)-4×10^(17)Ions/cm^2,室温注入。Auger谱表明,注入Ni^+,Mo^+使表面形成浓度达20—30at.-％的碳化层。组合注入形成较厚的表面非晶层,hcp结构的碳化物及fcc结构的奥氏体相。并对级联效应及辐照增强扩散对碳的渗入及形成非晶层的作用进行了讨论。     

Fe_3Al与水汽及氧气的表面反应

用ＡＥＳ及ＳＰＳ研究了Ｆｅ３Ａｌ与水汽及氧气表面反应动力学。表明二者的反应速度都很快，且都在１．５×１０－６Ｐａ·ｓ反应即开始当暴露量达１×１０－４Ｐａ·ｓ，水汽与Ｆｅ３Ａｌ反应达到稳定值，反应产物为Ａｌ２Ｏ３．Ｆｅ３Ａｌ与氧气的反应在１．５×１０－５Ｐａ·ｓ时达到稳定，此时主要是Ａｌ的氧化，当暴露量达３×１０－２Ｐａ·ｓ，Ｆｅ３Ａｌ与氧的反应达到第二阶段平衡，此时主要为Ｆｅ的氧化．上述表面反应动力学可用来圆满解释金属间化合物在不同环境气氛中的拉伸结果．     

Symmetry analysis of magnetic structures with a wave vector k<Subscript>6</Subscript> = μb<Subscript>3</Subscript> possible in the intermetallic compound Ce<Subscript>2</Subscript>Fe<Subscript>17</Subscript>

To estimate the reliability of literature data on the magnetic structure of Ce₂Fe₁₇, we performed a symmetry analysis of the possible magnetic structures characterized by the wave vector k ₆ = μb ₃ = 2π(0, 0, π/c). The previously developed procedure for calculating the basis functions of the irreducible representations of the space group D_3d ⁵ (R[`3]m)(R\bar 3m), which enter into the magnetic representation with the above wave vector, is described briefly and is employed for an analysis. The results of the calculations of these basis functions for Fe atoms located in 6c, 9d, 18f, and 18h positions are given and discussed. A conclusion is made that in this intermetallic compound there can exist magnetic structures of the type of longitudinal or transverse spin waves or of the type of a complicated spiral with the magnetic moment which varies according to a harmonic law as the coordinate z of the site occupied by the Fe atom changes.     

Protective Properties of Magnetron-Sputtered Cr–Si Layers on CoSb3

Pulse magnetron sputtering was used to deposit Cr–5Si (at.%) thin layers onto CoSb₃ substrates to prevent degradation of the material at elevated temperatures. The quality of the protective layers was evaluated on the basis of oxidation tests in air at 500 and 600 °C for up to 80 h. The surfaces, fractures and cross-sections of specimens were analyzed to assess integrity and adherence of the deposited layer as well as the extent of reaction and diffusion phenomena at interfaces. It was found that the Cr–5Si layer provided a satisfactory protection for CoSb₃ at 500 °C. Promising results were obtained at 600 °C.     

Mechanical characterization of hotplate synthesized vanadium oxide nanobelts

Vanadium oxide nanobelts have been synthesized on Si or SiN substrates by simply heating vanadium foils on a hotplate. As-grown nanobelts were characterized as V₂O₅·nH₂O (0.3 < n < 1.7) layer structures containing water molecular intercalation. Using an electromechanical resonance method, the Young’s modulus of the nanobelts was measured in situ in a scanning electron microscope. It was found that the Young’s modulus of as-grown nanobelts varied between 5.6 and 98 GPa, with a typical Q-factor of 120. Such scattered values were attributed to the different contents of water molecules in the nanobelts. After annealing at 450 °C in vacuum, the nanobelts were converted to α-V₂O₅ phase and a polycrystalline structure was observed. The Young’s modulus of the annealed nanobelts showed more consistent values at an average of 28.9 GPa, lower than the calculated modulus of bulk α-V₂O₅ at 68 GPa.     

The effect of ion implantation on the corrosion behaviour of pure iron—II. Chromium ion implantation

As part of a programme to investigate the effect of ion implantation on the corrosion behaviour of iron, pure iron specimens have been implanted with doses of 5 × 10¹⁴ and 2 × 10¹⁵ chromium ions/mm². Using a three-sweep potentiokinetic polarization technique the corrosion behaviour of these surface alloy layers has been compared with that of conventional binary FeCr alloys containing from 0.8 to 12.5 wt%Cr. It was found that apart from a slight thickening of the air-formed oxide film induced by the ion implantation process, the polarization behaviour of conventional alloys and of alloys produced by ion implantation was qualitatively very similar. Quantitatively the low dose chromium implanted specimens corresponded to a conventional Fe-4.9%Cr alloy while the high dose chromium implanted specimens resembled conventional alloys containing x12.5%Cr. These data provide a sound basis for the interpretation of the potentiokinetic polarization and corrosion behaviour of the novel surface alloy layers which can be produced by ion implantation.     

Phase diagram of magnetic structures in Fe/Cr/Fe films with nanoscale geometric inhomogeneities of interfaces

Results of an analysis of magnetic structures (mutual orientations of the iron-layer magnetizations) in three-layered Fe/Cr/Fe films formed due to the exchange interactions inside the layers of iron and chromium and on the Fe/Cr interfaces are given. The analysis was performed under the following assumptions: (1) the iron layers are ferromagnetic, and the magnetic structure of chromium layers has the form of transverse linearly polarized spin-density waves; (2) the iron-chromium exchange interaction is considered as a weak disturbance as compared to the exchange interactions inside the iron and chromium layers; therefore, they were considered as first-order and second-order perturbation-theory corrections; (3) the relative value of these corrections depends on the degree of roughness of the Fe/Cr interfaces; it was assumed that the roughness has a nanometer scale. With such approximations, the mutual orientation of the magnetizations of iron layers can be parallel, antiparallel, or noncollinear. The limits of stability of these structures depending on the thickness of the chromium interlayer and on the ratio of the first-to-second-order corrections have been determined. The main attention was paid to the conditions of the loss of stability with respect to changes in the phase of the spin-density wave, which can result in jumps in the curves of magnetization and magnetization reversal of the Fe/Cr films.     

Cyclic deformation and fatigue behaviour of 7Mo–0.5N superaustenitic stainless steel—slip characteristics and development of dislocation structures

The present work concerns the development of dislocation structures and surface slip markings during cyclic straining of a superaustenitic stainless steel. The composition of the tested material was Fe–25Cr–22Ni–7.6Mo–3Mn–0.46N (wt%). Two total strain amplitudes, 2.7×10⁻³ and 1.0×10⁻², were employed and specimens were investigated at specific numbers of cycles corresponding to certain stages on the cyclic hardening/softening curve. For both strain amplitudes, the developed dislocation structures are strongly planar and with increasing strain amplitude, the slip mode gradually changes from single slip to multiple slip. The short range ordering between Mo and N, as indicated by an atom probe investigation, is broken down during strain cycling leading to increased slip planarity. Early stages of cycling show dislocation multiplication. With increasing number of cycles, the dislocations are gradually grouped together in planar bands with high dislocation density, surrounded by dislocation-poor areas. The evolution of such bands is associated with decreasing effective stresses, while the internal stresses are only slightly reduced. Macroscopic slip bands, similar to PSBs, are formed upon prolonged cycling at the high amplitude. The slip markings created on the specimen surface show strong similarities with the bands of localised slip observed in the dislocation structures of the bulk.     

激光熔覆原位合成Mo2NiB2涂层工艺研究

目的选择和优化激光熔覆工艺参数,以制备三元硼化物金属基陶瓷Mo_2NiB_2涂层。方法通过激光熔覆原位合成法在碳钢表面制备了以Mo_2NiB_2为增强相的涂层,并采用金相显微镜、扫描电镜(SEM)及X射线衍射(XRD)对涂层组织进行分析。利用ANSYS计算熔覆过程的温度场,进而计算涂层凝固特征参数,即凝固形状控制因子。结果微观组织分析表明,在激光功率为2500 W、扫描速度为1.5 mm/s、预置厚度为1 mm时,可获得细密、均匀的组织,涂层中白色部分为生成的Mo_2NiB_2,灰色部分为Fe、Ni固溶体。涂层与基体结合部位以平面晶形式生长,然后以树枝晶的方式远离界面生长。温度场及凝固特征参数的计算表明,温度梯度达105℃/m数量级,形状控制因子达109(℃·s)/m~2数量级。结论激光功率的增加会使涂层中的枝晶组织趋于细密,形状因子K值大幅增大。凝固形状控制因子K为3×10~9~5×10~9(℃·s)/m~2时,凝固组织为平面晶,表现为"白亮带";K为7×10~9(℃·s)/m~2以上时,凝固组织为树枝晶;K为13×10~9(℃·s)/m~2时,树枝晶晶粒出现明显的细化现象。     

Microstructural evolution of Al-20Si-5Fe alloy during rapid solidification and hot consolidation

Al-20Si-5Fe melt was rapidly solidified into particles and ribbons and then consolidated to near full density by hot pressing at 400°C/250 MPa/1 h. According to the eutectic-growth and dendritic-growth velocity models, the solidification front velocity and the amount of undercooling were estimated for the particles with different sizes. Values of 0.43−1.2 cm/s and 15–28 K were obtained. The secondary dendrite arm spacing revealed a cooling rate of 6 × 10⁵ K/s for the particles with an average size of 20 μm. Solidification models for the ribbons yielded a cooling rate of 5 × 10⁷ K/s. As a result of the higher cooling rate, the melt-spun ribbons exhibited considerable microstructural refinement and modification. The size of the primary silicon decreased from approximately 1 μm to 30 nm while the formation of iron-containing intermetallic compounds was suppressed. Supersaturation of the aluminum matrix in an amount of ∼7 at.% Si was noticed from the XRD patterns. During the hot consolidation process, coarsening of the primary silicon particles and precipitation of β-Al₅FeSi phase were observed. Evaluation of the compressive strength and hardness of the alloy indicated an improvement in mechanical properties due to the microstructural modification.