金属玻璃的流变及弛豫行为研究

发布时间：2018-03-14 21:38

本文选题：金属玻璃　切入点：流变单元　出处：《中国科学院大学(中国科学院物理研究所)》2017年博士论文　论文类型：学位论文

【摘要】：金属玻璃因其优异的性能受到广泛的关注,如优异的力学性能、软磁性能、良好的微纳加工前景等。然而因其独特的长程无序结构,长久以来人们缺乏对金属玻璃的流变、弛豫、玻璃形成能力、玻璃转变等问题的本质认识。本文试图从流变单元角度解释金属玻璃的流变行为,调控金属玻璃的弛豫行为,发展新的金属玻璃体系。通过应力弛豫的方法从流变单元角度研究了金属玻璃在弹性区加载时,金属玻璃的微观结构随加载时间或应变变化时的演化规律。随着加载时间或加载应变的增加,金属玻璃中的流变单元逐渐被激活。流变单元的演化过程可以概括为流变单元的随机激活,协同运动以及贯通。通过调节冷却速率的方法研究了金属玻璃中流变单元浓度及自由体积的关系。随着冷却速率的增加,金属玻璃中的流变单元浓度及自由体积浓度均增加,金属玻璃的非均匀程度变大。同时,流变单元的浓度和自由体积的浓度存在着线性关系,从而利用控制冷却速率的方法调节金属玻璃中流变单元的浓度,进而调控金属玻璃的β弛豫行为。通过成分调控的方法制备出具有明显β弛豫的Fe基金属玻璃。随着Fe元素含量的增加,Fe基金属玻璃的β弛豫越明显。发现金属玻璃中Fe/Co/Ni等磁性元素的自扩散激活能与β弛豫的激活能基本相同。即Fe/Co/Ni等磁性元素在金属玻璃的β弛豫中起到重要作用。在稀土基金属玻璃及其他金属玻璃体系的动态力学弛豫谱中发现一种新的弛豫模式,即快β’弛豫。证实了快β’弛豫是金属玻璃及其形成液体的固有属性。得到金属玻璃快β’弛豫的激活能约为慢β弛豫激活能的一半。发现金属玻璃快β’弛豫激活能与金属玻璃局域原子运动的激活能近似相等,因此金属玻璃中的快β’弛豫可能起源于金属玻璃中原子的局域运动。利用模量规则,制备出具有较低玻璃转变温度的三元La-Ga-Cu块体金属玻璃体系。利用微量掺杂的方法,掺杂Fe,Co,Ni,Zr,Nb及Y元素都能将其形成能力由2~3 mm提高到大于5 mm。发现并证明镧镓基块体金属玻璃的反常晶化膨胀行为与镓元素有关。
[Abstract]:Metal glass has attracted wide attention for its excellent properties, such as excellent mechanical properties, soft magnetic properties, good micro-nano machining prospects, etc. However, due to its unique long-range disordered structure, the rheology of metallic glass has been lacking for a long time. This paper attempts to explain the rheological behavior of metallic glass from the angle of rheological unit and to regulate the relaxation behavior of metallic glass. A new metallic glass system was developed. The stress relaxation method was used to study the loading of metallic glass in elastic region from the rheological element point of view. The evolution of the microstructure of metallic glass with loading time or strain. The rheological units in metallic glass are gradually activated. The evolution of rheological units can be summarized as random activation of rheological units. The relationship between rheological unit concentration and free volume in metallic glass was studied by adjusting cooling rate. With the increase of cooling rate, the rheological unit concentration and free volume concentration in metallic glass increased. At the same time, there is a linear relationship between the concentration of rheological unit and the concentration of free volume, so the concentration of rheological unit in metallic glass is adjusted by the method of controlling cooling rate. The 尾 -relaxation behavior of metallic glasses was further regulated. Fe-based metallic glasses with obvious 尾 -relaxation were prepared by means of composition control. The 尾 -relaxation of Fe-based metallic glasses became more obvious with the increase of Fe content. The metal was found to be more obvious. The self diffusion activation energy of magnetic elements such as Fe/Co/Ni in glass is basically the same as that of 尾 relaxation. That is, magnetic elements such as Fe/Co/Ni play an important role in 尾 relaxation of metallic glass. A new relaxation mode has been found in the dynamic mechanical relaxation spectra of. It is proved that fast 尾 'relaxation is the intrinsic property of metallic glass and its liquid formation. The activation energy of fast 尾' relaxation of metallic glass is about half of that of slow 尾 relaxation activation energy. It is found that the fast 尾 'relaxation activation energy of metallic glass is about half of that of slow 尾 relaxation activation energy. The activation energy of local atom motion is approximately equal to that of metallic glass. Therefore, the fast 尾 'relaxation in metallic glass may originate from the local motion of atoms in metallic glass. Using the modulus rule, a ternary La-Ga-Cu bulk metallic glass system with low glass transition temperature was prepared. The formation ability of Fe _ (Co) Co _ (Ni) Ni _ (Zr) NB and Y elements can be increased from 2 ~ (3) mm to more than 5 mm. It is found that the abnormal crystallization and expansion behavior of lanthanum and gallium based bulk metallic glasses is related to gallium element.
【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG139.8

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