Sm(CobalFe0.1Cu0.1Zr0.033)6.9高温永磁合金的矫顽力

对Sm(Co_balFe_0.1Cu_0.1Zr_0.033)_6.9合金, 经810℃等温时效后以0.5℃/min逐渐冷却, 在600℃-400℃温度区间淬火, 研究了不同淬火温度下的磁滞回线、磁畴和矫顽力温度系数β. 发现时效600℃淬火后磁滞回线出现台阶状, 说明畴壁中应存在两处钉扎. 随淬火温度的降低, 合金的室温矫顽力显著增加, 磁滞回线的台阶消失. 通过磁畴形貌发现时效600℃淬火后的磁畴接近条形畴, 1:5相中Cu分布相对均匀, 形成的畴壁钉扎较弱, 从而使磁滞回线出现台阶, 决定矫顽力的畴壁钉扎位于两相界面处; 随时效淬火温度的降低, 磁畴逐渐细化, 畴壁1:5相中的畴壁能降低, 形成了较强的内禀钉扎, 并决定材料的矫顽力, 两相界面处的畴壁钉扎被掩盖. 对不同温度淬火合金的高温矫顽力研究表明, 最强的畴壁钉扎位于两相界面处时, 矫顽力随温度升高逐渐增加, 矫顽力出现温度反常现象; 最强的畴壁钉扎位于1:5相中心时, 矫顽力随温度升高逐渐衰减. 当测试温度达到500℃后不同淬火温度样品的矫顽力几乎相同, 此时最强畴壁钉扎均在两相界面处.     

超导In-Sn合金膜临界场的非线性非定域效应

本文对In+2％Sn,In+3％Sn的不同厚度合金膜的临界场H_c进行了研究,从实验上第一次提供了电子平均自由程l≠∞时的H_c～d的数据。这些实验结果表明,关于超导膜临界场问题只能用非线性非定域理论描述,在薄膜极限下,不论纯膜或合金膜,H_c∝d^-3/2;定域的London,Г-Л理论和线性非定域的Ittner理论皆不适用。一部分文献中给出H_c∝d^-1的结论,是由于那些作者分析实验结果的方法不恰当所致。     

Fe-Ga二元系平衡图

本文主要从X射线的研究,并配合差热分析,测定了1000℃以下的Fe-Ga二元系平衡图。这一系统在室温存在着三个居间相ε,χ和Ψ。ε相是有序面心立方结构,相当于理想化合式Fe₃Ga,相区范围很窄。在550℃上下,这个相转变为另一相ξ,这是在高温从Ga在Fe中的固溶体直接分出来的,这个高温相的结构尚未测定。χ相的均匀范围较大,在室温从55at.％Ga延伸到60at.％Ga,结构似乎非常复杂,可能的化合式是Fe₄Ga₅,Fe₃Ga₄或Fe₂Ga₃,这是在960℃上下由包晶反应形成的。Ψ相由另一包晶反应形成,反应温度为820℃,Ψ相属四方晶系,在20℃,α=6.2628?,c=6.5559?,空间群为D_4h¹⁴-P4₂/mnm,晶包内含四个化合式量FeGa₃。没有观察到Fe在Ga中有任何固溶度。从FeGa₃到Ga,存在着一条共晶等温线,共晶点非常接近纯Ga,在约590℃,存在着一条共析等温线,共析点在50at.％Ga左右,在这里Ga在Fe中的固溶体同时分解成ξ和χ。这个系统中最值得注意的是Ga在Fe中的原生固溶体。在室温的固溶度是15.2at.％,它随温度而逐渐递增,在700℃以上,则突增到约50at.％,在625℃以下的结构是体心立方体,在相图中用α代表。但在625℃以上,这个相又转变为两个不同的结构,并且各占据着一定的相域,在相图中各用α₁和α₂代表。α₁和α₂的结构尚未经测定,最可能是从α结构导生的、由基本单胞依照一定规律堆垜起来而产生的原子的重新排列或空位缺陷。     

γ′晶体的蠕变及持久性能

本文报导了对以Ni₃Al为基的r′单晶体所做的蠕变及持久试验的结果。结果表明,r′晶体的稳态蠕变速ε_s遵从 ε_s=Cσ^mexp(-Q_c′/RT) 的关系。指数m仅和温度有关。m(850℃)=3.95,m(950℃)=3.62。对Ni₃Al,Q_c′=88kcal/g-at。合金元素Ti,Nb,W都使Q_c′升高,其中Nb的作用最大,然而W在提高蠕变强度上最有效。晶体取向对ε_s有显著影响。<111>取向的Ni₃Al晶体ε_s最低,持久寿命t_r最长。在1050℃,σ=5kg/mm²时,t_r可≥100小时,Ni₃Al单晶体也同样符合Monkman-Grant关系t_r(ε_s)^p=常数,其中p=0.82。r′晶体蠕变中的滑移系统是{111}<211>。     

液Zn对Fe2Al5涂层侵蚀的相变过程研究

本文对Fe₂Al₅涂层在液态Zn中的侵蚀相变过程进行了研究,实验结果表明：在侵蚀初期,靠界面张力平衡的作用,先发生热侵蚀,在试样表面形成热蚀沟,当热蚀沟达到一定程度后, 液Zn与Fe₂Al₅相由不浸润变为浸润;同时Zn原子扩散进入Fe₂Al₅相并形成Fe₂Al₅-Zn_x固溶体相(η相);随着侵蚀时间的增加,发生在腐蚀界面上的液Zn对Fe₂Al₅涂层的侵蚀过程是恒温相变过程,相变过程使Fe₂Al₅涂层发生定向熔化. 相变的驱动力来自于相成分的改变所引起的各相自由能的变化及各相间的相平衡的重新建立.     

含有50原子%Zn的Ag-Au-Zn合金的研究

合金AgAuZn₂具有一个与郝斯勒合金同晶型结构的β″相,这个β″相存在于一个相当广阔的成分范围里。事实上,β″相就是β′有序结构的超结构。伴随着,β″结构的形成晶格发生突然的收缩。关于Ag-Au替换对于原子分布的影响,也作了系统的观察。在Ag-Au替换过程中,Au和Ag的替换或多或少是无规律性的,但Zn原子则仍保持它们的适宜位置,而不受到影响。当成分偏离于理想化学式AgAuZn₂时,有序度的减小不仅仅是由于化学成分的乖异,而且Ag-An替换也产生了一些无序的排列。高温观察的结果指出:Ag多合金的β′-β转变温度随着Au含量的增加而升高,而β相只能在高温度存在。少量的Au大大地提高了由淬炼而得到的β′相的稳定度。但是Au多的合金无论是在室温和高温都是具有β′结构的。     

机械合金化Fe-B合金的M?ssbauer谱研究

用M?ssbauer谱分析方法研究了配料原子比为Fe₇₀B₃₀,Fe₅₅B₄₅和Fe₃₀B₇₀各样品经机械合金化所形成的合金相的结构特点及其非晶相在退火过程中的转变。揭示出此类非晶相与相应的Fe-B化合物之间存在一定程度的联系。     

Y对Fe-Si-B 合金非晶形成能力及软磁性能的影响

本文通过铜模吸铸法和单辊甩带法分别制备出一系列楔形试样和非晶条带试样, 系统研究了稀土金属Y对Fe₇₈Si₉B₁₃合金非晶形成能力及其软磁性能的影响. 结果表明, 少量Y取代 Fe-Si-B 非晶合金中的Fe 可大大提高该合金的非晶形成能力并促进过冷液相区的产生. 当Y含量为3 at.%时, 合金具有最大的非晶形成能力, 其临界厚度为313 μm, 相应的非晶过冷液相区宽度达到65 K. 该系列非晶合金具有优良的软磁性能, 其矫顽力(H_c)均低于200 A/m, Y含量为1 at.%时, 饱和磁感应强度(B_s) 达到最大值1.67 T.     

Al-Cu-Fe二十面体准晶的深过冷研究

通过循环过热净化法研究了Ａｌ－Ｃｕ－Ｆｅ合金系中Al₆₅Cu₂₀Fe₁₅合金液的深过冷采用循环过热净化法净化Al₆₅Cu₂₀Fe₁₅合金液，获得了９８Ｋ的过冷度，并制备出直径为６ｍｍ的高纯度的Ａｌ－ＣＳ－ＦＳ二十面体准晶球．随着Al₆₅Cu₂₀Fe₁₅合金液过冷度的不同，Al₆₅Cu₂₀Fe₁₅合金液的第一形核相也发生变化．此外，提高对Al₆₅Cu₂₀Fe₁₅合金液的净化程度，可以提高合金液的形成Ａｌ－Ｃｕ－Ｆｅ二十面体准晶的能力．     

热处理对鑥铁氧体和锰铁氧体单晶铁磁共振的影响

本文观察了不同的热处理对于石榴石型的镥铁氧体(Lu₃Fe₅O₁₂)和尖晶石型的锰铁氧体(MnFe₂O₄)单晶的铁磁共振的影响。两次热处理分别为在700℃空气中加热1小时,和在700℃氧气中加热10小时,发现这样的热处理对K₁/M_s和g-因子无显著的影响,但却使共振线宽△H的各向异性显著减小,热处理对镥铁氧体的△H影响较小,但却使锰铁氧体的△H每经一次热处理后都成倍地增长。讨论了△H随热处理变化的原因,并由X射线衍射照相证实了锰铁氧体样品在热处理后有少量α-Fe₂O₃的脱溶。     

Decomposition of the solid solution and the formation of a high-coercivity state in Fe<Subscript>2</Subscript>NiAl alloy upon cooling at the critical rate

Transmission electron microscopy and magnetic measurements are used to study the formation of the microstructure and magnetic properties of Fe₂NiAl (alni) alloy upon cooling at the critical rate (V ～ 2°/min) from the region of single-phase solid solution (1240°C). Cooling is interrupted by water quenching caused by temperatures Т_quench. The periodical modulated structure formed during sample cooling at the critical rate guarantees the strongest possible coercive force (Н_с = 670 Oe). The decomposition of the solid solution below 900°C includes a stage of primary modulated structural failure upon continuous cooling to temperature Т_quench ～ 850°C, which corresponds to the weakest coercive force on the Н_с(Т_quench) curve. The periodical modulated structure is recovered when the temperature falls further; this is accompanied by an increase in the coercive force (up to Н_с = 670 Oe) after cooling to 20°C.     

Mössbauer study of Fe-B alloys containing Nd additives

The influence of a few percent neodynium additives to Fe-B alloy on the hyperfine parameters was investigated. It was found that Nd decreases the hyperfine field of amorphous Fe-B alloys. The samples annealed at temperatures between 600°C and 700°C contain α-Fe and Fe₃B phases. The average hyperfine field of Fe₃B phase increases with increasing Nd content and decreases with increasing annealing temperature. The average isomer shift of Fe₃B phase decreases with increasing Nd content. The experimental data show that the change of hyperfine parameters of the Fe₃B phase in the studied alloys is due to Nd atom.     

Microstructural evolution and phase transformation in the liquid-solid Al/Ni diffusion couple

The liquid-solid Al/Ni diffusion couple was successfully fabricated by annealing at 1373?K for 48?h followed by water-quenching. Cross-sectional scanning and transmission electron microscopic analyses show that the multilayered diffusion zones comprise the following sequence of layers: γ-Ni(Al) | γ′-Ni₃Al | β′-NiAl | Ni-rich β-NiAl | β-NiAl. The Ni-rich β-NiAl upon quenching undergoes a martensitic transformation from β (B2) to β′ (L1₀). The β′ martensite is found to be internally twinned on the {111}<112>system. The volume changes and strains due to martensitic phase transformation, the precipitation of γ′-Ni₃Al from γ-Ni(Al) and lattice mismatch between Ni-rich β-NiAl and β-NiAl in the Al/Ni diffusion couple are quantitatively determined. The cuboidal γ′ phase coherently precipitates cube-on-cube in γ-Ni(Al). Composition fluctuations existing in the supersaturated solid solution γ-Ni(Al), provide sufficient driving force for the precipitation and facilitate nucleation and growth of the γ′ phase under isothermal annealing.     

Thermal oxidation behaviors and structures of Fe-9Cr-1Mo alloy

Isothermal oxidation behaviors of Fe-9Cr-1Mo alloy were investigated at 600, 700, 750 and 850 ^°C for 72 h in air atmosphere. The oxidation rates were measured using a thermogravimetric analyzer (TGA). The structure and composition of the oxide scale were characterized by X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and conversion electron Mössbauer spectrometry (CEMS). In this study it was found that the oxide layers form duplex structures consisting of Fe and Cr oxides. CEMS spectra are composed of one doublet due to dispersed Fe ³⁺ in Cr₂O₃ oxidation layers produced at high temperatures and two magnetic components due to Fe-Cr-Mo alloy substrate and hematite (Fe, Cr)₂O₃ with lower hyperfine field than pure hematite (52 T). Fe rich oxides are formed at the surface by oxidation at relatively low temperatures of 600 ^°C and 700 ^°C, while Cr rich (Fe, Cr)-oxides are formed in the top surface layers by oxidation at higher than 750 ^°C.     

Fe-C—Sb合金中液态急冷获得的ε相的分解

本工作用示差热分析法,淬火样品X射线衍射法和Guinier-Lenn透射式高温单色聚焦粉末照相法研究了Fe-C-Sb合金中液态急冷获得的ε相的高温分解过程,实验结果指出,ε相在125℃开始分解,首先分解成ε-Fe₂C,而后在450℃分解成α-Fe,并析出Sb和Fe₃Sb₂,还保留有ε-Fe₂C;在550℃以后ε-Fe₂C转变成Fe₃C,并在770℃时发生Fe的α→γ转变,在800℃时主要组成相为:γFe,Sb,Fe₃C(Fe₃Sb分解);在冷却过程中750℃发生Fe的γ→α转变,冷至室温时的主要组成相是:αFe,Fe₃C,Sb,Fe₃Sb₂。 关键词：     

急冷Al-Si合金超导电性的研究

本文研究了热处理对急冷Al-11.3at％Si合金的微观结构及超导电性的影响,结构分析表明,液态淬火的样品由两相组成:过饱和α-Al(Si)固溶体晶体相和Al,Si原子按统计分布的非晶相,经100℃/50小时热处理后,α-Al(Si)固溶体贫化,非晶相中析出Si的小颗粒,经200℃/100小时热处理的样品已趋向平衡态结构,测量了样品的临界温度,在研究磁场中的超导-正常转变时发现了反常的磁阻效应,它可以用样品中存在两个超导相的模型予以解释。 关键词：     

Kinetics of cation-distribution variation in magnesium-manganese ferrites

Results are presented of an X-ray and neutron-diffraction investigation of the cation distribution as a function of the quenching temperature and isothermal-tempering duration for the ferrites Mg_1.093Mn_0.123Fe_1,784O_3.953 and Mg_0.812Mn_0.289Ni_0.062Fe_1.837O_3.998. To describe the kinetics of the ion redistribution in tempering, equations are proposed which satisfactorily describe the experimental curves. The magnetic moment, Curie temperature, and coercive force are investigated as a function of quenching temperature. The experimental data obtained are satisfactorily accounted for by Néel's theory of ferromagnetism.     

X-ray photoelectron studies of changes in the electronic structure upon phase transitions in Co–Ni and Co–Fe alloys

The changes in the electronic structure of Co–Ni and Co–Fe systems upon phase transitions are studied. X-ray photoelectron study of the valence-band spectra and the parameters of the multiplet splitting of Co, Ni and Fe 3s spectra is carried out at different temperatures. It is established that the ordering–separation phase transition in Co–Ni alloys takes place in the temperature range of 600–700°C. As opposed to Co–Ni alloys, in the Fe–Co alloy, ordering–separation–ordering phase transitions are observed. High-temperature ordering of the Fe₅₀Co₅₀ alloy is observed above 1200°C. The transition from ordering to separation is shown to lead to changes in the d electron spectra of the valence band and in the parameters of the multiplet splitting of the 3s spectra.     

In‐situ X‐ray diffraction of mechanically milled β‐Al3Mg2 powders

The structure evolution during heating of mechanically milled single‐phase β‐Al₃Mg₂ has been investigated by in‐situ X‐ray diffraction. The nanoscale supersaturated Al(Mg) solid solution formed during milling transforms back to the original β‐Al₃Mg₂ phase through a sequence of phase transformations. At low temperatures, an increasing amount of Mg is rejected from the solid solution with increasing temperature. At intermediate temperatures, the β′‐phase, a hexagonal phase with approximate composition Al₃Mg₂, forms. Finally, at higher temperatures the original β‐Al₃Mg₂ phase is restored, indicating that the formation of the supersaturated solid solution during milling can be reversed by appropriate heat treatment. The phase transformations during heating are gradual and the temperature ranges of stability of the different structure configurations are quite large, all exceeding 50 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Annealing effects on the microwave permittivity and permeability properties of Fe79Si16B5 microwires and their micowave absorption performances

This paper reports that amorphous magnetic microwires(Fe79Si16B5) have been fabricated by a melt-extraction technique and have been annealed at 600°C and 750°C respectively.Differential scanning calorimeter measurements show that nanocrystalline magnetic phase(α-Fe) has been formed in the amorphous matrix when it was annealed at 600°C.Hard magnetic phase(Fe2B) was formed in the microwires annealed at 750°C,which increases the magnetic coercivity.Microwave permittivity and permeability are found to be dependent on the microstructures.The permittivity fitting results show that multi Lorentzian dispersion processes exist.For microwires annealed at 750°C,their resonance peaks due to the domain wall movements and natural resonance are found higher than those of microwires annealed at 600°C.The microwave absorption performance of microwires annealed at 600°C is found better than microwires annealed at 750°C.