CuZr基合金玻璃形成能力的结构因素研究

发布时间：2018-05-11 03:08

本文选题：金属玻璃 + 玻璃形成能力　；参考：《南京航空航天大学》2017年硕士论文

【摘要】：非晶形成的微观结构影响因素一直是非晶态材料领域的研究热点。其中CuZr二元金属玻璃,成分简单而具有强玻璃形成能力(GFA),人们对其微观结构进行了大量研究。自由体积作为金属玻璃的一种独特结构参量广受关注,但是关于自由体积与GFA关联性的研究很少。另外,在CuZr基合金中,掺杂元素所引起的微观结构变化同样影响非晶的形成能力,对此人们也进行了大量研究。但关于微掺杂元素与母合金具有正混合热的体系,其GFA增强的微观结构机理尚不够清晰。在本文中,选择了CuZr和CuZrNb金属玻璃体系,从二元到三元,利用同步辐射技术结合计算模拟对非晶形成的结构影响因素进行了详细的研究。为了研究CuZr二元金属玻璃体系中自由体积和GFA之间的关联性,本文发展了一种用于探测金属玻璃中自由体积信息的新方法。我们发现自由体积的尺寸对非晶形成能力具有显著的影响。在具有GFA局部极大值的Cu64Zr36成分的微观结构中,计算得到的自由体积也呈现局部极大值,具有一一对应关系。金属玻璃的自由体积被认为与机械性能密切相关,从自由体积角度研究非晶的形成,有利于进一步探索微观结构与宏观性能的关系。此外,我们系统地研究了具有正混合热的CuZrNb金属玻璃体系,关注掺杂元素Nb引起结构变化从而导致GFA增强的现象。进行同步辐射X射线衍射和扩展X射线吸收精细结构实验,并对数据进行拟合得到微观结构模型,再采用Voronoi分形方法进行解析。发现在微量Nb元素(1-2 at.%)掺杂的CuZr合金体系中,Nb和Zr原子之间的电子轨道杂化导致原子对间距的缩短。进一步发现类二十面体局域结构的含量增加以及溶质原子Nb的分布更加弥散。上述因素均有利于增大原子空间堆积效率并形成短程到中程有序结构,从而导致金属玻璃的结构更稳定及GFA的相应增强。在正混合热的合金体系中,本工作为寻找具有高GFA的金属玻璃成分提供了理论依据。
[Abstract]:The factors affecting the microstructure of amorphous materials have been a hot topic in the field of amorphous materials. Due to its simple composition and strong glass-forming ability, CuZr binary metallic glass has been studied for its microstructure. As a unique structural parameter of metallic glass, free volume has attracted much attention, but the correlation between free volume and GFA is seldom studied. In addition, the microstructure changes caused by doping elements also affect the ability of amorphous formation in CuZr based alloys. However, the microstructure mechanism of GFA reinforcement in the system with microdoped elements and master alloy with positive mixing heat is not clear enough. In this paper, CuZr and CuZrNb metallic glass systems are selected, from binary to ternary, the influence factors of amorphous structure are studied in detail by synchrotron radiation technique combined with computer simulation. In order to study the relationship between free volume and GFA in CuZr binary metallic glass system, a new method for detecting free volume information in metallic glass is developed. We found that the size of free volume has a significant effect on the amorphous formation ability. In the microstructure of the Cu64Zr36 component with GFA local maximum, the calculated free volume also presents a local maximum, with a one-to-one correspondence. The free volume of metallic glass is considered to be closely related to mechanical properties. Studying the formation of amorphous from the angle of free volume is beneficial to further explore the relationship between microstructure and macroscopic properties. In addition, we have systematically studied the CuZrNb metallic glass system with positive mixing heat. We pay attention to the phenomenon that the doping element NB leads to the structural change, which leads to the enhancement of GFA. The fine structure experiments of synchrotron radiation X-ray diffraction and extended X-ray absorption were carried out. The microstructure model was obtained by fitting the data and then analyzed by Voronoi fractal method. It is found that the electron orbital hybridization between NB and Zr atoms in the CuZr alloy system doped with trace NB element at 1-2 at. leads to the shortening of the pair spacing. It is further found that the local structure of icosahedron increases and the distribution of solute atoms NB becomes more dispersed. The above factors are beneficial to increase the stacking efficiency of atomic space and form the ordered structure from short range to middle range, which leads to a more stable structure of metallic glass and the corresponding enhancement of GFA. In the alloy system with positive mixing heat, this work provides a theoretical basis for finding the composition of metallic glass with high GFA.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139.8

【参考文献】