Finemet-Co非晶合金的结晶动力学研究

利用标准的单棍甩带技术在大气环境下制备了Fe73.5-xCOxSi13.5B9Cu1Nb3 (x=10、30,50)非晶条带.在550和600℃下分别对非晶条带进行真空等温退火1h,从而在非晶基体中形成纳米晶相.X射线衍射(XRD)分析结果表明,550和600℃真空等温退火1h后,Fe73.5-xCOxSi13.5B9...     

V部分替代Nb对含Co FINEMET型合金磁性的影响

研究了含Co的Finemet型（Fe.．5Co0．5）73．5Nb3Si13．5B9Cu1和（Fe0.5Co0．5）73．5Nb2V1Si13．5B9Cu1合金在不同温度纳米晶化后的磁性．结果表明,用V部分替代Nb对淬态（Fe0.5Co0．5）73．5Nb2V1Si13.5B9Cu1非晶合金的居里温度没有明显的影响,但是形成（Fe0．5Co0．5）7a．5Nb2V1Si13．589Cu1纳米晶合金使剩余非晶中Co的含量降低,导致初始磁导率在高温下快速衰减;用V部分替代Nb使（Fe0．5Co0.5）73．5Nb2ViSi13．5B9Cu1纳米晶合金中的晶体相含有更多的Co,增大了材料的饱和磁感应强度B8并显著提高了初始磁导率．     

FINEMET合金晶化行为的DSC研究

本文通过非等温DSC方法研究了Fe73.5CulNb3Si13.5B9合金的晶化行为.根据不同升温速率的DSC曲线,采用Kissinger方程计算了两个析晶峰的晶化表观激活能E1(406±14kJ/mol)和E2(455±37kJ/mol)及频率因子ν(ν1＝3.15839×1022,ν2＝5.24126×1021);根据表观激活能与晶化分数的关系图分析了合金的晶化过程;最后利用JMA模型计算出两个析晶峰的Avrami指数m1(1.44)和m2(3.5),并根据动力学参数分析了非晶Fe73.5CulNb3Si13.5B9合金的析晶机理.     

Sm8Fe83Si2C5Cu0.5Nb1.5非晶合金的晶化动力学

用差热分析（ＤＴＡ）,结合Ｘ射线衍射（ＸＲＤ）研究了Ｓｍ８Ｆｅ８３Ｓｉ２Ｃ５Ｃｕ０．５Ｎｂ１．５非晶合金的晶化动力学。结果表明：温度在０￣１０００℃范围内,该合金的晶化相为α－Ｆｅ和Ｓｍ２（ＦｅＳｉ）１７Ｃｘ,α－Ｆｅ相的晶化表观激活能力３４９．５３ｋＪ／ｍｏｌ,Ｓｍ２（ＦｅＳｉ）１７Ｃｘ的晶化表观激活能力３１６．１９ｋＪ／ｍｏｌ,两相在晶化初期激活能量小,随晶化量（ｘｃ）的增加激活能增大,当α－     

Fe83Zr7B9Mn1非晶合金中α-Fe纳米晶化的HRTEM和结晶动力学研究

通过高分辨透射电子显微镜(HRTEM)和差示扫描量热法(DSC)研究了Fe83Zr7B9Mn1非晶合金中α-Fe纳米晶的结晶过程和非等温结晶动力学。通过HRTEM观察和X射线衍射分析,确定结晶析出相是α-Fe,在经过903K热处理之后,合金内部晶粒尺寸长大至20nm以上。对重叠放热峰进行了分峰拟合。利用Flynn-Wall-Ozawa方法确定了结晶过程的表观激活能Ea=260.3kJ/mol。进一步研究发现Fe83Zr7B9Mn1非晶合金中α-Fe纳米晶非等温结晶过程不适合用Johnson-Mehl-Avrami(JMA)模型描述,而可以利用esták-Berggren自催化模型进行描述。通过计算,α-Fe纳米晶结晶过程的指前因子以及转化函数分别为:lnA=30.6以及f(α)=α0.37(1-α)1.08。     

改性非晶和纳米晶FINEMET合金的显微硬度研究

本文研究了用元素W部分替代典型FINEMET合金中Nb和Fe的新型合金Fe73.3Cu1 Nb1 .5W1 .7Si1 3.5B9,在淬火态和不同退火温度及保温时间下 ,结合不同载荷大小和加载时间测试合金带芯部的显微硬度。随着纳米晶化的进行 ,自由体积缺陷含量和纳米晶晶界比例的变化会显著影响Fe73.3Cu1 Nb1 .5W1 .7Si1 3.5B9合金的显微硬度 ;合金在非晶态下有一定的压痕尺寸效应 ,而经过 4 5 0℃和 6 0 0℃退火 1h ,压痕尺寸效应消失 ;在 5 5 0℃退火温度下 ,在 0 .1kgf～ 0 .2kgf之间压痕尺寸效应不明显 ;合金的显微硬度变化趋势不符合超塑性波动公式。     

非晶Pr8Fe86B6合金的晶化动力学

用差热分析（DTA），结合X射线衍射（XRD）研究了非晶Pr8Fe86B6合金的晶化动力学。结果表明：该非晶Pr8Fe86B6合金的晶化相为α-Fe固溶体、Pr2Fe23B3和Pr2Fe14B金属间化合物，通过对三相晶化激活能的分析得出：α－Fe相的激活能在晶化初期变化不大，当其体积分数大于8％时，其晶化激活能开始减小；而Pr2Fe23B3和Pr2Fe14B相的激活能随其体积分数的增加而减小，且α－Fe相较Pr2Fe23B3和Pr2Fe14B相容易晶化析出。     

退火工艺对Finemet纳米合金磁性能的影响

为改善Finemet合金的磁性能,通过氩气退火和横、纵磁应力退火对合金进行热处理,研究退火工艺对合金磁性能及微观结构、形貌的影响.使用LCR数字电桥法、共地三电压法及冲击法测试磁性能,利用场发射扫描电镜观察Finemet合金的非晶、纳米晶形貌,采用X射线仪分析Finemet合金的结构.研究表明,540℃氩气退火使合金的初始导磁率μi达最高值且矫顽力H c最低,非晶基体出现bccα-Fe(Si)纳米晶颗粒,580℃氩气退火使纳米晶数量和尺寸增加,磁性能下降;540℃横磁退火可获得狭长扁平的磁滞回线、低剩磁比Br/Bs和铁损P c,540℃纵磁退火可获得矩形磁滞回线、高Br/Bs和P c,横、纵磁退火均使μi和H c降低.因此,合理的退火工艺可优化Finemet合金磁性能,以适应不同的应用领域.     

退火过程对非晶FeGeB合金磁性的影响

用单辊急冷法制得的FeGeB非晶条带,经退火处理后,发现其软磁性能下降.实验表明,在退火过程中有粗晶粒的Fe3Ge相形成,而没有观察到α-Fe相.由于Fe3Ge的晶粒尺寸超过铁磁交换作用长度,晶粒间各向异性常数不再相互抵消,引起了磁晶各向异性的增加,从而导致了样品的磁导率下降和矫顽力的上升.     

预退火对Sm5 Fe74.3Nb1.5Si11.7 B4.5C2.5Cu0.5非晶合金晶化动力学的影响

研究了预退火对Sm5Fe74.3Nb1.5Si11.7B4.5C2.5Cu0.5非晶合金晶化动力学的影响。结果表明，预退火处理使非晶合金晶化相α-Fe和Sm2Fe17Cx的晶化温度（Tp）和晶化表观激活能（Ec）值降低，且改变晶化相α-Fe在晶化过程中晶化激活能的变化趋势，有助于该合金在晶化退火中形成晶粒尺寸较小的α-Fe相。     

Effect of irradiation particle mass on crystallization of amorphous alloys

The crystallization temperature of amorphous alloys was found to be significantly lowered by heavy ion or electron irradiation during annealing. However, only heavy ion irradiation altered the mode of crystallization. Both a binary and multi-element amorphous alloy showed this type of response to irradiation. Radiation-enhanced diffusion processes in the amorphous state can explain the increased crystallization kinetics during irradiation. Heavy ion irradiation alters the crystallization mode by causing direct transformation to the final equilibrium phase as opposed to intermediate metastable phase formation during thermal annealing or electron irradiation. The equilibrium phase is believed to nucleate directly in the displacement cascades, which only form during heavy ion bombardment.     

Effect of composition on the crystallization and magnetic properties of Fe–Co–Si–B–Nb amorphous alloys

The crystallization behavior and magnetic properties of Fe₆₂Co₁₀Si_15−x B_18−y Nb_{(x + y)−5} amorphous alloys with x = 0–5 and y = 0–5 were examined. Primary crystallization temperature of Fe₆₂Co₁₀Si_15−x B₁₃Nb _x and Fe₆₂Co₁₀Si₁₀B_18−y Nb _y alloys increased with the addition of Nb. The primary and secondary crystallization temperatures were well separated when the Nb content is above 4 at%. The alloys with 15–18 at% B showed a distinct supercooled region. The Nb addition decreased the Curie temperature as well as room temperature saturation magnetization. The glassy-type Fe₆₂Co₁₀Si₁₀B₁₈ alloy exhibited good soft magnetic properties as well as a supercooled liquid region of 39 K. The finding of the glassy-type Fe-based alloy without Nb element exhibiting high Bs above 1.4 T is promising for future use as a soft magnetic glass material.     

Preparation and crystallization of chromium-based amorphous alloys

The glass formability of the Cr₇₂ (B, Si, C)₂₅Al₃ system has been investigated. Samples were prepared by rapid quenching from the melt by the melt spinning technique. Of the compositions investigated, only Cr₇₂B₁₀C₁₀Si₅Al₃ and Cr₇₁ C₁₇Si₈Al₃ formed fully amorphous alloys. These showed crystallization temperatures of 997 and 990 K, respectively, among the highest reported for transition metal-metalloid amorphous alloys. The crystallization products have been found to be Cr₇C₃ and Cr₃(Si, B) for Cr₇₂B₁₀C₁₀Si₅Al₃ and Cr₇C₃ and Cr₃Si for Cr₇₂C₁₇Si₈Al₃. The effects of substituting iron in place of chromium in Cr₇₂C₁₇Si₈AI₃ have been investigated. For up to 20 at% Fe the crystallization products are (Cr, Fe)₇C₃ and Cr₃Si. An alloy with 30 at% Fe crystallizes into (Cr, Fe)₇C₃ and hexagonal Cr-Si-C.     

Formation and crystallization of Al-Fe-Si amorphous alloys

Rapid solidification experiments of Al-based Al-Fe-Si ternary alloys have been performed both by the gun and single roller methods. Glass forming tendency is found to be largest near theβ-phase (Al₉Fe₂Si₂) composition, where the amorphous state is obtained both by the gun and single roller methods. Crystallization behaviour of amorphous AlFe_13.0Si_17.4 alloy, nearβ-phase composition, followed the course of (i) the appearance of fineα-Al particles and (ii) the transformation of the matrix intoβ-phase. The ratio of crystallization temperature and the melting point,T _x/T _m, for AlFe_13.0Si₂17.4 amorphous alloy is smaller than 0.5 indicating the difficulty of glass formation of these alloys.     

Study of the crystallization kinetics in amorphous Fe73.5Cu1Nb3Si13.5B9 alloy

The kinetics of the crystallization of Fe_73.5Cu₁Nb₃Si_13.5B₉ amorphous alloy was studied using Mössbauer spectroscopy and X-ray diffractometry. During isothermal annealing of the samples, two phases were observed: a crystalline D0₃-FeSi alloy with fine grains and an amorphous phase enriched with niobium, boron and copper. It was found that the growth rate of the particles of the crystalline alloy was controlled by diffusion. For longer annealing time or at higher annealing temperature the growth process was found to be suppressed, probably by the niobium atoms. The activation energy obtained for the crystallization was about 143 kJ mol^–1.