循环处理对Fe基非晶合金微观结构、晶化及磁性能的影响

采用XRD、DSC、TEM等检测方法,研究了深冷循环处理、473K退火循环处理及冷-热循环处理对Fe_(68)Ni_1Al_5Ga_2P9 (6.5)B_(46)Si_3C_(6.75)非晶合金的微观结构、晶化过程及磁性能的影响.结果表明:经不同的循环处理后,试样仍然保持非晶结构,发生了结构弛豫,微观结构改变.但与淬态试样相比,玻璃转变温度、晶化温度及晶化峰值温度存在一定的变化.退火品化后,各试样中析出相的种类、数量、晶粒尺寸等有明显的不同.磁性能数据表明:品化后,循环处理的试样其磁性能较淬态有所提高.     

双喷嘴快淬法制得的非晶/晶体Fe_(55)Ni_(20)Cu_5P_(10)Si_5B_5

正Krzysztof Ziewiec等人采用双喷嘴快淬法制造Fe_(40)Ni_(40)P_(10)Si_5B_5和Fe_(70)Cu_(10)P_(10)Si_5B_5合金混合物,是两种液相不互溶的合金。根据Fe_(70)Cu_(10)P_(10)Si_5B_5合金试验,选择适宜快淬温度。双喷嘴快淬制得Fe55Ni20-Cu5P10Si5B5合金,晶体沿非晶带和非晶/晶体的快淬方向排列。Fe_(55)Ni_(20)Cu_5P_(10)Si_5B_5合金由于加热而晶化,析出带状微结构。双喷嘴得到的非晶相比单一喷嘴快淬法多。对双喷嘴快淬法制得的合金的结构、相成分     

辊速及晶化工艺对(Nd, Pr)13Fe80Nb1B6快淬薄带组织和矫顽力的影响

用熔体快淬法制备(Nd,Pr)_(13)Fe_(80)Nb_1B_6快淬薄带并晶化处理,研究辊速和晶化条件对其组织和矫顽力的影响.结果表明,在10～20、25和35 m/s分别得到纳米晶、部分非晶和完全非晶薄带,且在18 m/s制备的薄带有较好的c轴各向异性.快淬态薄带的矫顽力随辊速(10～25 m/s)的增大而增加.非晶薄带晶化后由(Nd,Pr)_2Fe_(14)B相和富稀土相组成,且完全非晶薄带晶化后比部分非晶薄带晶化后的矫顽力要高,这是由于前者比后者具有更均匀的微结构造成的.非晶薄带晶化后矫顽力最大为1616 kA/m,高的矫顽力与添加Pr和Nb有关.     

退火温度与时间对Co46Fe20B23.5Si4.5Nb6非晶合金软磁性能的影响

采用铜模吸铸法成功制备了直径为1 mm的Co_(46)Fe_(20)B_(23.5)Si_(4.5)Nb_6非晶棒材,随后在570～800℃对该非晶合金进行等温退火处理,研究退火温度及时间对其晶化行为及软磁性能的影响。结果表明:Co_(46)Fe_(20)B_(23.5)Si_(4.5)Nb_6非晶合金的玻璃转化温度(T_g)为582.95℃,第一次晶化温度为(T_x)为636.53℃,过冷液相区(ΔT)为53.58℃。铸态Co_(46)Fe_(20)B_(23.5)Si_(4.5)Nb_6非晶合金具有良好的软磁性能,其饱和磁化强度为74.82 emu/g,矫顽力为3.34 G。经过570℃或620℃退火,非晶合金的软磁性能得到明显提高,其中在620℃退火保温5 min后合金得到最大的饱和磁化强度(79.51 emu/g)和最小的矫顽力(1.02 G),具有最优的软磁性能。     

非晶(Fe_(0.1)Ni_(0.35)Co_(0.55))_(78)Si_8B_(14)和Fe_(40)Ni_(38)Mo_4B_(18)合金的磁导率弛豫

在0—300℃间研究非晶(Fe_(0.1)Ni_(0.35)Co_(0.55))_(78)si_(?)B_(14)和Fe_(40)Ni_(38)Mo_4B_(18)合金的可逆磁导率等温弛豫行为.给出等时弛豫谱,观察到三个弛豫峰.计算弛豫时间的分布和最可几激活能.初步考查Curie温度以上的退火和较慢冷却对弛豫动力学的影响.对这两种成分截然不同的合金观察到十分相似的动力学行为,表明磁寻率弛豫主要是由基本结构缺陷的局域运动引起的,成分的影响则十分次要.     

MAGNETIC PERMEABILITY RELAXATIONS IN AMORPHOUS ALLOYS(Fe_(0.1)Ni_(0.55)Co_(0.55))_(78)Si_8B_(14) AND Fe_(40)Ni_(38)Mo_4B_(18)

在0—300℃间研究非晶(Fe_(0.1)Ni_(0.35)Co_(0.55))_(78)si_(?)B_(14)和Fe_(40)Ni_(38)Mo_4B_(18)合金的可逆磁导率等温弛豫行为.给出等时弛豫谱,观察到三个弛豫峰.计算弛豫时间的分布和最可几激活能.初步考查Curie温度以上的退火和较慢冷却对弛豫动力学的影响.对这两种成分截然不同的合金观察到十分相似的动力学行为,表明磁寻率弛豫主要是由基本结构缺陷的局域运动引起的,成分的影响则十分次要.     

几种非晶态铁磁合金的磁导率稳定性的估计

本文根据非晶态铁磁合金的磁导率衰减动力学的实验数据得到的经验公式,利用平均激活能和频率因子的实验值估计了预退火的非晶合金Fe_(76)Si_(10)B_(14),Fe_(40)Ni_(38)Mo_4B_(18)和(Fe_(0.1)Ni_(0.35)Co_(0.55))_(78)Si_8B_(14)的起始磁导率的相对稳定程度。计算结果表明,虽然不能实质上消除磁导率的不稳定性,但是大约在不超过100℃的温度范围内,磁导率相对稳定程度对实际应用是足够的。换句话说,在相当长时间内,磁导率衰减相当小。     

Fe_(41)Co_7Cr_(15)M_(0.14)Y_2C_(15)B_6非晶合金的力学性能和磁性

正P.Rezaei Sahreza等人研究退火时Fe_(41)Co_7Cr_(15)M_(0.14)Y_2C_(15)B_6非晶合金力学性能和磁性变化,研究结果表明,退火过程该非晶合金晶体中含有Fe_(23)(B_4C)6、Mo_3Fe_3C及Mo_3Co_3C等相。928℃退火时这些相的体积分数增加到32.3%。借助压痕试验研究本试验的块状非晶合金的力学性能,通过分段式研磨得到Palmqvist裂纹的裂纹系统种类。通过提高退火温可以同时提高硬度和刻痕韧性。增加结晶相体积分数,也     

高频低损耗FeNi基非晶态合金的磁性及热稳定性试验

从实用观点出发,本试验在Fe_(40)Ni_(38)B_(22)成分基础上,研究了加入过渡族或类金属元素对磁性(Tc、Tcr、Ms (RT) Hc、P)及热稳定性的影响.用单辊急冷法制了Fe_(40)Ni_(38)X_(26)B_(22-26)系合金,试样经X光检验确认为非晶态.     

Fe_(52-x)Co_(14)Nb_4Mo_3Ni_5B_(22)Cr_x多组元块体非晶合金的热学和软磁性能

采用铜模铸造法制备Fe_(52-x)Co_(14)Nb_4Mo_3Ni_5B_(22)Cr_x(x=0, 2, 3, 4; at.%)多组元块体非晶合金。采用X射线衍射仪(XRD)、差示扫描量热分析仪(DSC)和振动样品磁强计(VSM)等手段探究了Cr含量对合金非晶形成能力及软磁性能的影响。DSC曲线表明,合金经历2次晶化过程,Cr含量增加使得合金成分接近深共晶点。随着Cr含量的增加,合金的过冷液相区ΔTx由36 K增加到51 K,晶化起始温度Tx1由842 K增加至872 K。VSM结果表明,Fe_(52-x)Co_(14)Nb_4Mo_3Ni_5B_(22)Cr_x非晶合金其饱和磁感应强度Ms随着Cr含量的增加而减小。制备得到的多组元块体非晶合金具有高非晶形成能力和优异软磁性能,适合于作为一款优异的磁性元器件材料使用。     

离子辐照对Zr50.7Cu28Ni9Al12.3非晶合金力学性能的影响

非晶合金有潜力成为新一代核材料,离子辐照对其力学性能的影响决定了其使用价值。在不同剂量的Au离子辐照下,探讨了Zr_(50.7)Cu_(28)Ni_9Al_(12.3)非晶合金力学性能的变化过程。原子力显微镜以及正电子湮没寿命谱分析表明,在离子辐照后,非晶合金的自由体积尺寸增大、密度下降,总自由体积增加。透射电子显微镜分析表明,辐照剂量在达到50 dpa时非晶合金开始有纳米晶析出,随着辐照剂量的增加,纳米晶尺寸在增加、密度变大。纳米压痕试验表明,离子辐照后非晶合金的硬度减小,在高剂量时硬度又有增加的趋势。离子辐照下非晶合金的硬度变化是自由体积以及纳米晶竞争的结果。自由体积使非晶合金软化,纳米晶析出使非晶合金硬化。     

Formation, properties and microstructure of amorphous/crystalline composite Ag20Cu30Ti50 alloy using miscibility gap

The aim of the work was to produce the amorphous/crystalline composite with uniform distribution of fine crystalline soft phase. Silver–copper–titanium Ag₂₀Cu₃₀Ti₅₀ alloy was prepared using 99.95 wt% Ag, 99.95 wt% Cu, 99.95 wt% Ti that were arc-melted in argon atmosphere. Then the alloy was melt spun on a copper wheel with linear velocity of 33 m/s. Investigation of the microstructure for both arc-melt massive sample and melt-spun ribbons was performed with use of scanning electron microscope (SEM) with EDS, light microscope (LM) and X-ray diffraction. The thermal stability was evaluated by differential scanning calorimetry (DSC). The properties such as Young modulus and Vickers hardness number before and after crystallization of the amorphous matrix were measured with use of nanoindenter. The microstructure was investigated by transmission electron microscope (TEM). It was found, that the alloy has a tendency for separation within the liquid state due to the miscibility gap which resulted in segregation into Ti–Cu–Ag matrix and Ag-base spherical particles after arc-melting. During rapid cooling through the melt spinning the Ag₂₀Cu₃₀Ti₅₀ alloy formed an amorphous/crystalline composite of fcc silver-rich spherical particles within the amorphous Ti–Cu–Ag matrix.     

Structural, microstructural and magnetic properties of amorphous/nanocrystalline Ni63Fe13Mo4Nb20 powders prepared by mechanical alloying

This paper focuses on the magnetic, structural and microstructural studies of amorphous/nanocrystalline Ni₆₃Fe₁₃Mo₄Nb₂₀ powders prepared by mechanical alloying. The ball-milling of Ni, Fe, Mo and Nb powders leads to alloying the element powders, the nanocrystalline and an amorphization matrix with Mo element up to 120 h followed by the strain and thermal-induced nucleation of a single nanocrystalline Ni-based phase from the amorphous matrix at 190 h. The results showed that the saturation magnetization decreases as a result of the electronic interactions between magnetic and non-magnetic elements and finally increases by the partial crystallization of the amorphous matrix. The coercive force increases as the milling time increases and finally decreases due to sub-grains formation.     

Influence of thermally induced structural transformations on hardness in Fe89.8Ni1.5Si5.2B3C0.5 amorphous alloy

Effect of heat treatment on mechanical behavior of Fe_89.8Ni_1.5Si_5.2B₃C_0.5 amorphous alloy was investigated by measuring microhardness. It was shown that the as-prepared amorphous alloy has an unexpectedly high microhardness. This can be attributed not only to boron dispersed in the alloy, but also to the structure which exhibits aspects of a nanocomposite of nanoparticles dispersed in an amorphous matrix. As the alloy crystallizes at temperatures above 540 °C, microhardness decreases continuously as a function of heating temperature. This is attributed to separation of boron out of the amorphous matrix into nanocrystals of Fe₂B phase. Further decrease in microhardness is attributed to crystallite growth with the accompanying change in the dominant nature of the interfaces from amorphous/crystal to crystal/crystal, and creation of a porous structure. When the crystallization is complete, the alloy exhibits microhardness close to that of a hypothetical mixture of α-Fe and Fe₂B phases of the same composition.     

Corrosion behaviour of the amorphous Mg65Y10Cu15Ag10 alloy

The corrosion behaviour of the amorphous Mg₆₅Y₁₀Cu₁₅Ag₁₀ alloy as well as of its crystalline multiphase counterpart was studied in alkaline electrolytes and compared with that of the amorphous Mg₆₅Y₁₀Cu₂₅ alloy. Electrochemical investigations were carried out in 0.3 M H₃BO₃/Na₂B₄O₇ buffer solution with pH=8.4 and in 0.1 M NaOH solution with pH=13. Tafel plots were recorded and cyclic potentiodynamic polarisation tests were conducted, transients were measured at anodic potentials. Potentiostatically formed surface layers were characterised by Auger electron spectroscopy and atomic force microscopy. Changes in the corrosion behaviour were noticed which are attributed to the presence of silver. The passive layers formed in the two electrolytes were quite different in the composition as well as in morphology. The layer growth mechanisms also showed some variation presumably mainly due to the presence of silver, though copper still seems to play a dominant role in the passivation of this alloy in the weakly alkaline solution. The amorphous alloys displayed superior corrosion behaviour compared to the crystalline alloy, because of the absence of the heterogeneties existing in crystalline alloys.     

Effect of quenching on magnetostriction and microstructure of melt-spun Fe83Ga17 alloy

The effect of quenching on magnetostriction and microstructure of melt-spun Fe₈₃Ga₁₇ ribbons was investigated. The results show that magnetostriction of ribbons is greatly improved by heat treatment and the value of λ of ribbons reached nearly −2300 ppm after annealed at 700 °C for 3 h. The XRD analyses reveal that the microstructure of melt-spun Fe₈₃Ga₁₇ alloy ribbons was changed after heat treatment and the transition of A2 + DO₃ → A2 + DO₃ + DO₁₉ occurred at 700 °C for the ribbons. The magnetostriction of Fe₈₃Ga₁₇ ribbons is influenced by the emergence of DO₁₉ structure and the increase of ordered degree, and the variation of crystallinity of A2 phase is also related to the magnetostriction of Fe₈₃Ga₁₇ ribbons.     

Effects of cryogenic treatment on the thermal physical properties of Cu<Subscript>76.12</Subscript>Al<Subscript>23.88</Subscript> alloy

The thermal diffusion coefficient,heat capacity,thermal conductivity,and thermal expansion coefficient of Cu76.12Al23.88 alloy before and after cryogenic treatment in the heating temperature range of 25°C to 600°C were measured by thermal constant tester and thermal expansion instrument.The effects of cryogenic treatment on the thermal physical properties of Cu76.12Al23.88 alloy were investigated by comparing the variation of the thermal parameters before and after cryogenic treatment.The results show that the variation trend of the thermal diffusion coefficient,heat capacity,thermal conductivity,and thermal expansion coefficient of Cu76.12Al23.88 alloy after cryogenic treatment was the same as before.The cryogenic treatment can increase the thermal diffusion coefficient,thermal conductivity,and thermal expansion coefficient of Cu76.12Al23.88 alloy and decrease its heat capacity.The maximum difference in the thermal diffusion coefficient between the before and after cryogenic treatment appeared at 400°C.Similarly,thermal conductivity was observed at 200°C.     

Structure and crystallization kinetics of a Cu50Zr45Ti5 glassy alloy

The crystallization kinetics and structure changes in a melt-spun Cu₅₀Zr₄₅Ti₅ glassy alloy on heating were investigated by X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry and differential isothermal calorimetry. The glassy phase in the Cu₅₀Zr₄₅Ti₅ alloy was crystallized forming Cu₁₀Zr₇ and CuZr₂ phases upon thermal annealing. The activation energy for crystallization obtained by the Arrhenius equation was 435 kJ/mol. The crystallization process took place by nucleation and growth mechanism, and an Avrami exponent of about 3.3 may indicate a three-dimensional interface-controlled growth of nuclei with a decreasing nucleation rate.     

Magnetic entropy changes at early stages of nanocrystallization in amorphous Fe90Zr7B3 ribbons

Microstructure, revealed by transmission electron microscopy and conventional Mössbauer spectroscopy, magnetization versus magnetizing field induction and temperature and isothermal magnetic entropy changes in the as-quenched and subjected to annealing at T_a1 = 723 K for 2 or 3 h and at T_a2 = 743 K for 2.5 h of Fe₉₀Zr₇B₃ amorphous alloy are studied. In the as-quenched state the medium range ordered regions are observed. The annealing at T_a1 leads to early stages of crystallization and nanograins with different diameter embedded in amorphous matrix are formed. At the Curie point of the amorphous phase they are magnetically decoupled and behave like superparamagnetic particles. The Curie point of the residual amorphous phase shifts towards higher temperature as compared to the as-quenched state due to the Invar like effect. The peak of the isothermal magnetic entropy changes appears at the Curie temperature of the main amorphous phase. Their values at the maximum applied field of 0.75 T equals to 0.32 J/kg K⁻¹ in the as-quenched alloy and remain almost unchanged after early stages of nanocrystallization. After the annealing at T_a2 the peak of the entropy changes distinctly decreases. Such behavior is ascribed to the biphasic character of the sample. The main amorphous phase and ordered one, which in some circumstances can be treated as an assembly of superparamagnetic particles, contribute to the total magnetic entropy changes.     

Thermal behaviour of Pd40Cu30Ni10P20 bulk metallic glass

The thermal behaviour of differently milled Pd₄₀Cu₃₀Ni₁₀P₂₀ bulk metallic glass through the glass transition has been investigated by in situ high-energy synchrotron X-ray diffraction. Repeated heating and cooling were performed between the glassy and the supercooled liquid state. The changes in positions and intensities of the first and second diffraction maxima of the as-milled powder indicate irreversible changes during first heating up to the glass transition temperature T_g due to structural relaxation. After annealing, reversible structural changes with temperature are observed upon heating and cooling in the glassy phase, and in the supercooled liquid state respectively. The shift in the position of the first maximum scales approximately with the linear thermal expansion for the glassy state; however, this relation does not hold for the supercooled liquid. The structural transition from the glass to the supercooled liquid at the glass transition temperature is reflected by the intensity of the diffraction maxima and by a reversed temperature dependence of the position of the second diffuse maximum below and above T_g. The changes of the glass structure for the decrease of free volume by annealing are found to be different from those observed for the reversible volume expansion or shrinkage by varying the temperature. Therefore, the shift of the first diffuse maximum position of bulk metallic glasses cannot be used as a measure of the change in free volume.