Nb对非晶态Fe-Co-Nd-B合金的晶化动力学的影响

在Fe-Co-Nd-B非晶合金中添加4%的Nb(原子分数)可延迟其晶化过程, 提高晶化温度, 并使其热稳定性显著提高. Nb抑制Fe₃B晶化相的形核, 但促进Fe₂₃B₆相的形核及长大. Nb可使晶化相的平均晶粒尺寸从30-60 nm减至14-20 nm. Nb使由初始晶化温度计算的晶化激活能明显降低. Fe-Co-Nd-B合金中, α-Fe(Co), Fe₃B和Nd₂(Fe, Co)₁₄B晶化相的形核过程要难于长大过程, 而加Nb后α-Fe(Co), Fe₂₃B₆和Nd₂(Fe, Co)₁₄B晶化相的长大过程要难于形核过程, 但Nb基本未改变晶化相的形核及长大机制. 非晶合金的晶化主要是一维界面控制的形核以及形核率随时间减小的三维长大过程.     

CRYSTALLIZATION PROCESS AND NON–ISOTHERMAL CRYSTALLIZATION KINETICS OF MELT–SPUN Nd–Fe–B AMORPHOUS THICK RIBBONS

利用熔体快淬法在12 m/s的辊速下制备了Nd₆Fe₇₂B₂₂和Nd₆Fe₆₈Ti₄B₁₇C₅非晶厚带. 通过DSC和XRD, 并借助Kempen模型和 Kissinger方程, 研究了合金的非晶晶化过程及非等温晶化动力学. 结果表明, 两种合金厚带具有不同的晶化过程以及晶化动力学机制. Nd₆Fe₇₂B₂₂合金的晶化过程分为三步完成: 非晶
相 (AP)→ Nd₂Fe₂₃B₃→Nd₂Fe₁₄B+ α--Fe +Fe₃B→Nd₂Fe₁₄B+α--Fe+Fe₃B+NdFe₄B₄, 而Nd₆Fe₆₈Ti₄B₁₇C₅ 合金一步完成晶化: AP→Nd₂(Fe, Ti)₁₄(B, C)+α--Fe + Fe₃B. 与Nd₆Fe₇₂B₂₂合金由界面控制的多晶型晶化不同, Nd₆Fe₆₈Ti₄B₁₇C₅合金以扩散控制的共晶型晶化为主.     

Cu含量对新型AlNiZrCoYSi高熵非晶合金非晶形成能力与耐腐蚀性能的影响

采用高真空电弧熔炼喷射成形技术制备了一种新型Al_17.5Ni₂₀Zr_17.5Co₂₀Y₂₀Si₅高熵非晶合金条带,并研究了Cu元素的添加及含量变化对Al_17.5Ni₂₀Zr_17.5Co₂₀Y₂₀Si₅高熵非晶合金耐腐蚀性能的影响。利用X射线衍射仪(XRD)、差示扫描量热仪(DSC)、显微硬度计分别研究了合金材料的非晶形成能力与硬度;通过极化曲线(Tafel)和Nyquist图等电化学方法考察了高熵非晶合金室温下在3.5 wt.% NaCl水溶液中的耐腐蚀性能。结果表明：四种(AlNiZrCo)_75-xCu_xY₂₀Si₅(x=0, 10, 14, 15)近等原子比高熵非晶合金均呈现典型的非晶态衍射峰,Cu含量对AlNiZrCoYSi高熵非晶合金的非晶形成能力影响不大,但会降低合金的抗腐蚀性能,且上述合金的维氏显微硬度均超过470 HV_0.1。其中,Al_17.5Ni₂₀Zr_17.5Co₂₀Y₂₀Si₅高熵非晶合金的耐腐蚀性能最佳,其自腐蚀电位(E_corr)为-0.248 V,自腐蚀电流密度(i_corr)为1.63 μA/cm^₂,极化电阻(R_p)为24.56 kΩ.cm^₂,该材料在解决严苛海洋环境下防腐耐磨问题具有较大的应用潜力。     

Ce17Fe78-xB6Mx (M=Cu, Al, Ga; x=0-1.0)快淬合金永磁性能研究

本文基于熔体快淬技术,研究了低熔点元素Cu、Al和Ga添加对Ce₁₇Fe₇₈B₆合金磁性能的影响。三类低熔点元素的加入,均降低了合金的磁化强度,而矫顽力有一定程度的提升。其中,Cu和Ga元素添加可优化晶粒尺寸分布,且Ga添加对Ce₁₇Fe₇₈B₆合金矫顽力的提升最为有效。研究发现,Ce₁₇Fe₇₈B₆合金回复曲线轻微开口;当Ga添加量为0.75 at.%时,合金具有较优异的综合磁性能,回复曲线完全闭合。适量Ga元素添加明显增强了Ce-Fe-B基合金晶间短程交换耦合作用,减小了合金平均回复磁导率,有效降低了Ce-Fe-B基合金在周期性反向磁场中的能量损失。     

B和Ce对Co-8.8Al-9.8W-2Ta合金组织和性能的影响

为了改善Co-8.8Al-9.8W-2Ta合金的性能,添加0.4at.%的Ce元素和B元素,研究其对基体合金组织和性能的影响。结果表明：Ce元素和B元素均可以抑制二次相析出,并对二次相有球化作用;0.4Ce合金晶界区域析出Co₃W相,Ce元素主要形成化合物Ce₂Co₁₇和Al₂Ce₂Co₁₅,0.4B合金晶界区域析出Co₃W和Co₇W₆相,B元素主要形成CoW₂B₂;Ce元素和B元素均可以提高合金的显微硬度,0.4Ce合金显微硬度最高。     

铁基非晶合金带材压磁现象测试与表征方法改进及其压磁特性

本文在无接触式电感方法基础上自主开发改进了一套新的测试系统,改进的测量装置可以表征铁基非晶合金带材的压磁特性。研究表明,在σ≤0.1 MPa下,Fe_73.5Cu₁Nb₃Si_13.5B₉非晶带材具有良好的圧磁特性,在测试条件lev=0.3V 、f=1 kHz时,Fe_73.5Cu₁Nb₃Si_13.5B₉非晶带材均在多次试验中均表现出很好的稳定性和重复性。带材对微小应力极为敏感,在对带材进行初步施压时,样品的电感值出现迅速上升趋势,通过放大实验进一步精确了带材的应力敏感区间约在0-1.5 KPa之间;不同厚度和宽度的Fe_73.5Cu₁Nb₃Si_13.5B₉非晶带材对其压磁性能具有较大影响,测量的电感初值及其相应的SI(%)Max值总体上随着相应尺寸的增加而增大;带材宽度一定时,33-36 mm厚带材的压磁性能最优, 相应的SI(%)Max为19.8%;带材厚度一定时,20 mm宽的带材具有更加优异的压磁性能,其SI(%)Max高至22.02%。     

具有高非晶形成能力的高熵合金Cu29Zr32Ti15Al5Ni19

用铜模吸铸法成功地合成了由两个固溶体相构成的高熵合金(HEA) Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉和相同成分的非晶态合金(HE-BMG)。实验结果表明该成分的高熵合金具有高的非晶形成能力。铸态高熵合金Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉的抗压强度为1127MPa。在750℃保温2小时后的Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉高熵合金的硬度仍高达826HV。     

EFFECT OF Gd ADDITION ON THE GLASS FORMING ABILITY AND MECHANICAL PROPERTIES IN A Zr–BASED BULK AMORPHOUS ALLOY

适量的Gd掺杂可提高Zr_50.7Cu₂₈Ni₉Al_12.3块体非晶合金的玻璃形成能力, 当Gd元素掺杂量 (原子分数) 为1%时, 即(Zr_50.7Cu₂₈Ni₉Al_12.3)₉₉Gd₁, 柱状非晶合金直径可达16 mm (不掺杂时为14 mm). 稀土Gd掺杂降低了锆基块体非晶合金的断裂强度与塑性 变形能力. 随着Gd含量的增加, 其断裂方式由单一的剪切断裂转变为剪切断裂与破碎断裂的复合形式, 且含Gd元素掺杂的非晶合金断口呈现了脉状纹络与纳米周期性条纹共存的特征.     

(Zr55All0Ni5Cu30)0.97Ce0.03非晶合金在含Cl-介质中的腐蚀电化学行为研究

  用电化学技术方法研究了Zr₅₅Al_l0Ni₅Cu₃₀和(Zr₅₅Al_l0Ni₅Cu₃₀)_0.97Ce_0.03非晶合金在含Cl^-介质中的腐蚀电化学行为及添加稀土Ce的影响.结果表明：随Cl^-浓度增加,两种非晶合金的腐蚀速度加快;添加稀土Ce后提高合金耐蚀性;随极化电位的提高,两种非晶合金在0.05 mol/L Na₂SO₄及含Cl^-介质中均出现钝化特征,维钝电流密度随Cl^-浓度增加而减小;Zr₅₅Al_l0Ni₅Cu₃₀非晶合金的电化学阻抗谱由单容抗弧组成(Zr₅₅Al_l0Ni₅Cu₃₀)_0.97Ce_0.03非晶合金的交流阻抗谱在Cl^-浓度较低时呈单容抗弧特征,而随Cl^-浓度的增加,单容抗弧变为双容抗弧.     

Cr元素对Fe基块体非晶合金形成能及腐蚀性能影响的研究

利用微合金化技术,制备了Fe_68.4-xCo_7.6Si₇B₁₀P₅C₂Cr_x (x=0, 1, 2, 3)非晶合金,并分别使用单辊急冷甩带法和铜模铸造法制备了带状和棒状样品。借助XRD、DSC、DTA表征该非晶合金系的热力学性能与非晶形成能;并进一步采用电化学动电位极化曲线法研究了该非晶合金系在硫酸溶液中的的耐腐蚀性能。实验结果表明,通过微量添加Cr元素的方法,使该合金系的非晶形成能普遍提高,当Cr元素添加量为2%时,获得了该系列非晶合金中的最大过冷液体区间(ΔTx=57K),并且成功制备了直径为5mm的圆棒状样品;同时,由于Cr元素的添加,在1N浓度的硫酸溶液中,材料表面上形成富含Cr元素的保护层,可以有效阻止材料内部的进一步腐蚀,耐腐蚀性能明显得到改善。     

Effect of Cu and Mo Additions on the Crystallization Behavior and Magnetic Properties of Fe<Subscript>80</Subscript>Zr<Subscript>10</Subscript>B<Subscript>10</Subscript> Alloy

Fe₈₀Zr₁₀B₁₀, Fe₈₀Zr₁₀B₉Cu₁, and Fe₈₀Zr₈Mo₂B₁₀ amorphous alloys were prepared by melt-spinning and annealed at various temperatures. The effect of Cu and Mo additions on the thermal property, microstructure and magnetic properties of Fe₈₀Zr₁₀B₁₀ alloy is studied. Both Cu and Mo additions decrease the crystallization activation energy. The crystallization process of Fe₈₀Zr₁₀B₁₀ alloy is very complex. Both Cu and Mo additions simplify the crystallization process. But a few α-Mn-type phase is still observed in the initial crystallization stage of Mo-containing alloy. Both Cu and Mo additions increase saturation magnetization (M _s) and decrease coercivity (H _c) of alloys. The addition of Cu is beneficial to decrease H _c in the initial crystallization stage, and the addition of Mo is beneficial to decrease H _c at high temperatures.     

Critical cooling rate and thermal stability of Fe–Co–Zr–Y–Cr–Mo–B amorphous alloy

The critical cooling rate of the Fe₆₁Co₅Zr₈Y₂Cr₂Mo₇B₁₅ bulk amorphous alloy was determined to be 37 K/s, providing an indication that this alloy has a high glass-forming ability. The non-isothermal crystallization kinetics of the Fe₆₁Co₅Zr₈Y₂Cr₂Mo₇B₁₅ amorphous alloy prepared by using the copper-mold casting or melt-spinning were also investigated. It is found that the activation energies in the non-isothermal crystallization process show a strong dependence on the cooling rates for glass formation, revealing that the melt-spun amorphous alloy has a higher thermal stability.     

High temperature oxidation behavior of FeCo‐based nanocrystalline alloys

This paper describes the dynamic and isothermal oxidation behavior of three different FeCo‐based Fe_38.5Co_38.5Nb₇Cu₁B₁₅, Fe₃₆Co₃₆Nb₇Si₁₀B ₁₁ and Fe_33.5Co_33.5Nb₇Si₁₅B₁₁ alloys and one traditional FINEMET Fe₇₃Nb₃Cu₁Si_15.5B_7.5 alloy. Dynamic and isothermal oxidation measurements in controlled oxidizing atmosphere were performed and the oxidation apparent energy as well as the oxidation behavior was obtained. SEM observations were carried out in order to characterize the oxide layer formed during the oxidation measurements. The apparent activation oxidation energy found for the Fe₃₆Co₃₆Nb₇Si₁₀B₁₁, Fe_33.5Co_33.5Nb₇Si₁₅B₁₁ and Fe₇₃Nb₃Cu₁Si_15.5B_7.5 alloys was about 35 kJ/mol and for the Fe_38.5Co_38.5Nb₇Cu₁B₁₅ alloy was about 70 kJ/mol.     

Fe- and co-based nanocrystalline soft magnetic alloys modified with Hf, Mo, and Zr: Magnetic properties, thermal stability, and structure. Alloy (Fe0.7Co0.3)88Hf4Mo2Zr1B4Cu1

The alloy (Fe_0.7Co_0.3)₈₈Hf₄Mo₂Zr₁B₄Cu₁ is studied to obtain materials with improved thermal stability. The effect of the nanocrystallization conditions that occur during heat treatment (HT) and thermomechanical treatment (TMechT) in air at temperatures of 520–620°C on the structure of the alloy, as well as its magnetic properties and their thermal stability, is considered. Longitudinal magnetic anisotropy is shown to be induced in the alloy in the course of TMechT; the easy magnetization axis of the anisotropy is parallel to the long side of the ribbon. The alloy specimens subjected to heat and thermomechanical treatment have different magnetic characteristics. The (Fe_0.7Co_0.3)₈₈Hf₄Mo₂Zr₁B₄Cu₁ alloy is found to surpass the (Fe_0.6Co_0.4)₈₆Hf₇B₆Cu₁ and (Fe_0.7Co_0.3)₈₈Hf₇B₄Cu₁ alloys studied in [1] in the thermal stability of the magnetic properties. The magnetic properties of the alloy after nanocrystallization, which occurs in the course of TMechT (σ = 250 MPa) at 620°C for 20 min, hardly change during annealing at 550°C for 26 h.     

Influence of partial substitution of Ge on crystallization kinetics, microstructure and magnetic property of Fe44Co44−xZr7B5Gex alloys

Partial substitution of Ge for Co in Fe₄₄Co₄₄Zr₇B₅ amorphous alloy is found to have a large influence on crystallization kinetics and magnetic property of the alloy. Activation energy of nanocrystallization of FeCo phase (primary crystallization) decreases by 90 kJ/mol with 4 at.% Ge substitution, while that of precipitations of Zr-type phase from a residual amorphous phase (secondary crystallization) increases by 106 kJ/mol. The suppression of the secondary crystallizations stabilizes the FeCo nanocrystals embedded in the residual amorphous phase for the Fe₄₄Co_44−xZr₇B₅Ge_x until higher temperatures. It is proposed that the stabilization mechanism is attributed to preferential partitioning of Ge in the residual amorphous phase revealed by scanning transmission electron microscopy analysis. Microstructure and coercivity for the annealed alloys are also presented in combination with the effect of the Ge substitutions.     

Crystallization mechanism of Fe78Si13B9 amorphous alloy induced by ion bombardment

The crystallization behavior of Fe₇₈Si₁₃B₉ amorphous alloys induced by Ar ion bombardment was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. The crystallization process of amorphous alloys can be controlled by adjustment of ion incident angles (θ), beam density and substrate temperature. The compressive stress caused by ion bombardment will result in the decrease of critical nucleation energy and induce the crystallization of amorphous alloy even at very low temperature, and the thermal effect converted from energetic ions will improve the crystallization of amorphous alloys. The crystallization process of amorphous alloy induced by ion bombardment was a stress induced phase transformation process assisted by thermal effect.     

Thermal stability and crystallization of Zr–Al–Cu–Ni based amorphous alloy added with boron and silicon

The amorphous Zr_65−x−yAl_7.5 Cu_17.5Ni₁₀Si_xB_y alloy ribbons, x=1–4 and y=1–2, with 0.1 mm thickness were prepared by melt spinning. The thermal properties and microstructure development during the annealing of amorphous alloys were investigated by the combination of differential thermal analysis, differential scanning calorimetry, X-ray diffractometry, and TEM. Both of the glass transition temperature and the crystallization temperature for Zr_65−x−yAl_7.5 Cu_17.5Ni₁₀Si_xB_y alloys increases with the silicon and boron additions and reaches 674 and 754 K, respectively for Zr₆₀Al_7.5 Cu_17.5Ni₁₀Si₄B₁ alloy. The highest T_rg (0.62) and γ value (0.43) occurred at the Zr₆₀Al_7.5Cu_17.5Ni₁₀Si₄B₁ alloy. In addition, the Zr₆₀Al_7.5Cu_17.5Ni₁₀Si₄B₁ alloy was revealed to have the highest activation energy of crystallization (about 370 kJ/mol as determined by the Kissinger plot). This value is about 20% higher than the activation energy of crystallization for the Zr₆₅Al_7.5Cu_17.5Ni₁₀ based alloy (314 kJ/mol). In parallel, the alloy 4Si1B also performs a longer incubation time at higher isothermally annealing temperature. All of the evidence implies that Zr₆₀Al_7.5 Cu_17.5Ni₁₀Si₄B₁ alloy exhibits the highest thermal stability among those alloys in this study. The crystallization behavior for the alloy 4Si1B isothermally annealed at the supercooled temperature region for different time has also been examined by TEM and discussed.     

Structural transformations of amorphous iron-based alloys upon abrasive and thermal treatments

Wear resistance and structural changes have been investigated in amorphous alloys Fe₆₄Co₃₀Si₃B₃ and Fe_73.5Nb₃Cu₁Si_13.5B₉ upon wear using a fixed abrasive. The structural studies have been performed by the methods of metallography, electron microscopy, and Mössbauer spectroscopy. It has been shown that the abrasive resistance of amorphous alloys is 1.6–3.1 times lower than that of high-carbon tool steels, which have a close level of hardness. The low abrasive wear resistance of amorphous alloys is caused by the deformation softening of the alloy surface in the process of wear. The major volume of the deformed surface layer of the alloys preserves the amorphous state. Its structural changes upon wear are characterized by the formation of inhomogeneities (fragments with a size of 10–50 nm) and by a decrease in the width of the strongest “halo” in the selected-area electron-diffractions patterns. In the amorphous matrix of the Fe₆₄Co₃₀Si₃B₃ alloy, a strong magnetic texture is formed and a redistribution of atoms occurs, which leads to an increase in the local shortrange order corresponding to FeB, Fe₂B, Fe₃B and α-Fe phases. In microvolumes of a thin (several μm) surface layer, the formation of a nanocrystalline structure (on the order of several volume %) was revealed. A tempering of the Fe_73.5Cu₁Nb₃S_13.5B₉ alloy at temperatures below 500°C does not affect the hardness and wear resistance of the alloy. At 500°C, there occurs an increase in microhardness and wear resistance of the Fe_73.5Cu₁Nb₃S_13.5B₉ alloy as a result of the formation in it of a nanocrystalline structure with the retention of a certain amount of the amorphous phase. The complete crystallization of the alloy at 540°C increases the brittleness of the alloy, which leads to a sharp reduction in its wear resistance.     

The correlation of microstructural development and thermal stability of mechanically alloyed multicomponent Fe-Co-Ni-Zr-B alloys

The microstructural evolution of multicomponent Fe_70-x-yCo_xNi_yZr₁₀B₂₀ (x = 0, 7, 21; y = 7, 14, 21, 28) alloys during mechanical alloying (MA) has been studied using XRD, SEM and TEM. Mixtures of elemental and pre-alloyed powders have been transformed initially into the single supersaturated bcc α-Fe solid solution phase for the alloys investigated. Subsequently, an amorphous phase has been obtained in Co-free alloys and Co-containing alloys with high Ni/Co ratios of 1 and 3. However, no amorphous phase was detected in another Co-containing alloy with a lower Ni/Co ratio (e.g. 0.33). The thermal stability of the as-milled powders has been investigated by a combination of DSC and the Pendulum magnetometer experiments. The DSC studies provide information on the thermodynamics and kinetics of crystallization of amorphous structure as a function of alloying contents. The Pendulum magnetometer studies reveal the phase transformation from nanocrystalline bcc α-Fe solid solution to amorphous structure during MA and the thermomagnetization behavior of the as-milled powder.     

Glass-forming ability of RE–Al–TM alloys (RE=Sm,Y; TM=Fe,Co, Cu)

The glass-forming ability (GFA) of RE–Al–TM (RE=Sm, Y; TM=Fe, Co, Cu) upon melt-spinning and die-casting into a copper mold has been studied. Melt-spun ribbons for both Sm- and Y-based alloys show a fully amorphous structure. However, die-casting revealed that Sm-based alloys exhibit a higher GFA than Y-based alloys. The as-cast Sm₇₀Fe₂₀Al₁₀, Sm₆₀Fe₂₀Al₁₀Co₁₀ and Sm₆₀Fe₂₀Al₁₀Co₅Cu₅ cylinders (3 mm×50 mm) contain a mixture of amorphous and crystalline phases after copper-mold casting. A new bulk metallic glass was obtained for the Sm₆₀Fe₁₀Al₁₀Co₁₅Cu₅ alloy, which shows ferromagnetic behavior. In contrast, as-cast Y-based alloys are completely crystalline. Based on the data of the activation energy for crystallization of the amorphous phase, E_x, and the crystallization temperature, T_x, together with magnetic measurements, it is concluded that the as-cast Sm₆₀Fe₁₀Al₁₀Co₁₅Cu₅ cylinder displays a tendency for clustering. The improved glass-forming ability of Sm-based alloys is interpreted in terms of classical nucleation theory.