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在600~930 K,常压到7 GPa的范围内,对非晶(Fe0.99,Mo0.01)78Si9B13合金等温等压退火30 min。实验表明:其晶化产物α-Fe(Mo, Si)、Fe3B和Fe2B相的析出与所加压力密切相关。压力使非晶(Fe0.99,Mo0.01)78Si9B13合金的晶化温度和亚稳Fe3B相的析出温度下降,在一定的压力和温度下,亚稳Fe3B相将向稳定Fe2B相转变,其转变温度随压力而变化。还对非晶(Fe0.99,Mo0.01)78Si9B13合金的晶化和亚稳Fe3B到稳定Fe2B转变的热力学机制进行了讨论,并给出Fe3B向Fe2B的相转变方程。 相似文献
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本文研究了Fe40Ni40P12B8非晶合金冲击波加载下的晶化行为,冲击波由二级轻气炮发射的告诉弹丸撞击靶产生。实验结果表明:Fe40Ni40P12B8非晶合金在冲击波加载下,晶化可在加载时间(微秒量级)内发生;晶化的阈值压力在30~50 GPa之间,相应的冲击温度约为510~800 K,晶化析出相与冲击压力有关,低压下析出相是面心立方γ-(Fe, Ni)固溶体和Fe3(P0.37B0.63)化合物,高压下(大于60 GPa)析出相除了面心立方γ-(Fe, Ni)固溶体和Fe3(P0.37B0.63)化合物之外,还包括(Fe, Ni)3P化合物。 相似文献
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本文研究了Pd40Ni40P20块状非晶在4 GPa及常压下的晶化过程。得到了时间-温度转变图。结果表明:高压下样品的晶化温度明显升高,压力对原子的长程扩散及相分离熔体的粘性流动均有抑制作用。在接近熔点进行高压退火时,获得了单相过饱和固溶体。其晶体结构为面心立方。 相似文献
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高压下与Al发生扩散反应的非晶(Fe0.99Mo0.01)78Si9B13(FMSB)的晶化产物与纯FMSB的不同。与Al反应的FMSB非晶在3.0~5.0 GPa、780~900 K热处理时,晶化为α-Fe(Al)和次亚稳非晶合金;在这一压力范围以外,720~900 K热处理时,晶化为α-Fe(Si)、Fe3B或Fe2B。与Al发生反应的FMSB非晶可能通过与Al的扩散反应在Al/FMSB界面开始晶化。压力和温度对晶化过程的影响主要是由于α-Fe固溶体的Gibbs自由能随压力、温度和Al含量的变化。 相似文献
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An equiatomic nanocrystalline NiTi alloy, deformed by high-pressure torsion (HPT), was investigated. The as-prepared bulk NiTi alloy consisted of both amorphous and nanocrystalline phases. Crystallization and structural changes during annealing were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and transmission electron microscopy (TEM). DSC thermograms and X-ray analyses revealed stress relaxation and partial crystallization below 500?K, while grain growth of the nanocrystals occurred predominantly after heating to temperatures above 573?K. Along with the amorphous phase crystallization, a continuous growth of pre-existing nanocrystals that are retained after HPT was observed. The DSC signals observed during continuous heating experiments indicate an unusually large separation between the crystallization and growth stages. A detailed analysis of the evolution of the enthalpy release upon annealing revealed reproducibly non-monotonous trends with annealing temperature that cannot be explained solely by nucleation and growth of crystalline volume fractions. Instead, the results can be rationalized by assuming a reverse amorphization process occuring during annealing at 523?K. This behavior, which also caused a large variation in nanocrystal size after annealing at higher temperatures, is discussed with respect to the nanoscale microstructural heterogeneity after initial deformation processing. 相似文献
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The results obtained by partially substituting Ge for B and Si in the FINEMET alloy for the purpose of improving its magnetic properties at high temperatures are presented in this work. Nanocrystalline ribbons were obtained from controlled crystallization of amorphous material made employing the melt spinning technique. The studied compositions were: Fe73.5Si13.5Ge2Nb3B7Cu1 and Fe73.5Si13.5Ge4Nb3B5Cu1. The structural evolution of these alloys was studied using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) and these results were correlated with their magnetic properties at different annealing temperatures. The coercivity obtained for both alloys was below 1 A/m at anneling temperatures between 773 and 823 K. The amorphous saturation magnetization was satisfactory, almost 137 emu/g, comparable with that obtained for FINEMET alloys. The nanocrystallization and the Curie temperatures are dependent on Ge concentration. 相似文献
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利用X射线衍射技术、差示扫描量热分析技术和透射电子显微镜研究了非晶态Cu56 Zr4 4合金的结构及其等温退火条件下的晶化过程 .实验结果表明 ,非晶态Cu56 Zr4 4合金在室温下的短程结构类似于硬球无规密堆积分布 .在70 3K过冷液相区内等温退火时发现 ,当退火时间为 3min时 ,晶化产物主要为Cu8Zr3相 ;当退火时间为 6min时 ,Cu8Zr3相完全消失 ,而Cu1 0 Zr7相大量析出 ;当退火时间达到 3 0min以上时 ,其晶化产物转变为Cu1 0 Zr7,CuZr2 ,Cu8Zr3等多种化合物 .由此提出了非晶态Cu56 Zr4 4合金等温退火晶化过程的扩散机理 . 相似文献
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The local atomic environment of a melt-spun Ni25Ti50Cu25 amorphous alloy and bond evolution during crystallization were studied by extended X-ray absorption fine structure (EXAFS) spectroscopy and differential scanning calorimetry. In the amorphous alloy, the interatomic distances of Ni–Ti and Cu–Ti are distinct from Ti–Ti and can be indicative of the formation of two types of dominant polyhedra or distorted polyhedral clusters centered with Ni and Cu, with the majority of shell atoms being Ti. The overall increase in the coordination numbers of Ni, Ti, and Cu by crystallization and evidence for structural relaxation suggest that the melt-spun ribbon contains a combination of ordered structures and free volume prior to the heat treatment. Copper and nickel are co-located as their absorption spectra are similar. Although crystallization occurs rapidly (within 4?min at 500 °C), the local atomic environment change persists at longer annealing durations (up to 10?min). An increase in the Ti–Ti and Cu–Cu homo-bond fractions at short and intermediate annealing times suggests that these species segregate between Cu-rich and Cu-poor phases. Crystallization continues through a short-range Ti and Cu diffusion-dominated process, as the near-neighbor structures of Ti and Cu change considerably more than for Ni during annealing. This homogenizes the microstructure followed by possible precipitation of a TiCu compound. 相似文献
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采用XeCl准分子激光对非晶碳化硅(a-SiC)薄膜的脉冲激光晶化特性进行了研究.通过原子力显微镜(AFM)和Raman光谱技术对退火前后薄膜样品的形貌、结构及物相特性进行了分析.结果表明,选用合适的激光能量采用激光退火技术能够实现a-SiC薄膜的纳米晶化.退火薄膜中的纳米颗粒大小随着激光能量密度的增加而增大;Raman谱分析结果显示了退火后的薄膜的晶态结构特性并给出了伴随退火过程存在的物相分凝现象.根据以上结果并结合激光退火特性,对a-SiC的脉冲激光晶化机理进行了讨论.
关键词:
激光退火
晶化
碳化硅 相似文献