The nano-scale structure observed by neutron diffraction for the metastable materials synthesized by mechanical alloying

近年来，由于机械合金化（MA）的固态非晶化过程中进行了大量的工作。已知机械合金化工艺中的固态反应在不同组分的界面处进行，并因此取决于各种研磨条件，例如研磨强度、环境温度、本文主要利用中子衍射技术的优点进行了结构观察，以了解机械合金化过程的机理。进行特征在于正混合热的Cu-Ta体系。通过中子衍射和EXAFS的原子级结构分析以及低温比热和XPS价带结构中超导转变的电子学研究证实了非晶相的形成。MA或Cr-Fe和Cr粉末在氮气气氛下形成非晶相。在Cr-Fe-N和Cr-N体系中，氮原子位于六个Cr原子形成的多面体的中心，并稳定非晶结构。由于在氮气气氛下的MA过程中的固-气反应，观察到的Cu-V系统，这也是不混溶的非晶化。采用Mg-Al-Zn、Ni-Zr和Se系合金研究了球磨强度和环境温度对准晶和非晶形成的影响。据证实，这两个参数的影响显着完成相应的相的形成所需的时间。研磨强度总是被发现在缩短研磨时间方面是有效的。另一方面，在结晶温度低的系统中，环境温度对形成过程的影响更显著。

Recently a considerable amount of work has been performed on the solid-state amorphization process due to mechanical alloying(MA). Teh solid state reaction in the mechanical alloyig process is known to proceed at the interface of different components and thereby to depend on various milling conditions such as milling intensity, the ambient temperature, atmosphere and so on. In this study in order to understanding the mechanism of the mdchanical alloying process the structural observation was carried out mainly by using the advantage of the neutron diffraction technique.The MA of the Cu-Ta system, which is characterized by a positive heat of mixing, was carried out. The formation of an amorphous phase was confirmed by the atomic level structure analysis of neutron diffraction and EXAFS and by the electronic studies through a chage in the superconducting transition in the low-temperature specific heat and XPS valence band structure. The MA or the Cr-Fe and Cr powders under the nitrogen gas atmosphere formed an amorphous phase. The nitrogen atom is located at the center of the polyhedron formed by six Cr atoms and stabilizes the amorphous structure in the Cr-Fe-N and Cr-N systems. The amorphization of the Cu-V system, which is also immiscible, was observed due to the solid-gas reaction during the MA under the nitrogen gas atmosphere. The Mg-Al-Zn, Ni-Zr and Se systems were used to elucidate the effect of the milling intensity and ambient temperature on the formation of the quasicrystal and amorphous phase. It is confirmed that both parameters affect significantly the time necessary to complete the formation of the respective phases. The milling intensity is always found to be effective in shortening the milling time. On the other hand, the ambient temperature affects the formation process more significantly in the system where the crystallization temperature is low.