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首页> 外文会议>International Symposium on Metastable and Nano-Materials(ISMANAM-2005); 20050703-07; Paris(FR) >Phase separation and nanocrystal formation in Al-based metallic glasses
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Phase separation and nanocrystal formation in Al-based metallic glasses

机译：铝基金属玻璃的相分离和纳米晶体形成

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摘要

Nanocrystallization in a group of Al-RE and Al-RE-TM (RE = rare earth, TM = transition metal) melt-spun amorphous alloys was studied using in situ small- and wide-angle X-ray scattering techniques (SAXS/WAXS) and transmission electron microscopy (TEM). The SAXS/WAXS i measurements were carried out during isothermal annealing at temperatures close to crystallization point. A continuously growing interference maximum shifting progressively toward lower angles was found to develop in SAXS regime. Simultaneously taken WAXS spectra reveal formation of the primary fcc-Al nanocrystalline phase. The presence of the SAXS signal maximum indicates the spatial correlation between the compositional fluctuations. The peak position decay is an evidence of an increase of the fluctuation spacing characteristic for the coarsening stage of phase separation. The SAXS/WAXS data analysis indicates that amorphous phase decomposition triggers and controls the fcc-Al nanocrystalline phase formation. The glassy phase initially decomposes into Al-rich and RE-rich regions with typical lengths scale of about l0nm. The nanocrystals nucleate preferentially inside the Al-rich amorphous regions and their growth is constrained by the region size because of the sluggish atomic diffusion in the RE-rich zones. A different crystallization mechanism is demonstrated in Al-Y-Ni-Co glass where WAXS spectra show formation of the fcc-Al primary phase but no interference peak in SAXS regime was found.
机译：使用原位小角度和广角X射线散射技术（SAXS / WAXS）研究了一组Al-RE和Al-RE-TM（RE =稀土，TM =过渡金属）熔纺非晶态合金的纳米晶化）和透射电子显微镜（TEM）。 SAXS / WAXS i测量是在等温退火过程中，在接近结晶点的温度下进行的。发现在SAXS体制中逐渐形成了一个不断增长的干扰最大值，逐渐向较小的角度移动。同时获得的WAXS光谱揭示了主要的fcc-Al纳米晶相的形成。 SAXS信号最大值的存在指示成分波动之间的空间相关性。峰位置衰减是相分离的粗化阶段波动间隔特性增加的证据。 SAXS / WAXS数据分析表明，非晶相分解触发并控制了fcc-Al纳米晶相的形成。玻璃态相最初分解成富含铝和富含稀土的区域，其典型长度约为10nm。纳米晶体优先在富铝非晶区域内成核，并且由于富稀土区域中的原子扩散缓慢，其生长受到区域尺寸的限制。在Al-Y-Ni-Co玻璃中证实了不同的结晶机理，其中WAXS光谱显示形成了fcc-Al初生相，但在SAXS范围内未发现干扰峰。

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