The Observation of Quasicrystal-Quasicrystal Phase Transition in Al-Pd-Mn Icosahedral Phase

本研究的主要目的是研究Al-Pd-Mn二十面体相的准晶-准晶相变。有报道称Al_<71>Pd_<21>Mn_8二十面体相不仅是f型二十面体相，还可以是f2型和f2m型二十面体相。我们增加了对f2m型相位的研究。在Al_<71>Pd_<21>Mn_8附近的合金成分中，f型二十面体相稳定在800℃左右，其名称来源于面心立方思想的6 dim超立方晶格。了解f2型和f2m型二十面体相。我们增加了对f2m型相位的研究。f2m型很容易理解为f2型二十面体相的6点菱形晶格。我们试图研究未知的f2m型二十面体相的特征，我们称之为介质相，以及f2型和f2m型二十面体相的生长条件。我们已经获得了准晶体稳定性的知识。未知的f2m型二十面体相特征：F…More 2m型不是真正的二十面体相，而是具有三角或立方对称性。它具有通常的晶体对称性，但是是准周期的。f2型和f2m型二十面体相的生长条件：在此条件下进行了搜索；将高温退火条件定在T=803-806 C, 50 h，控制第二次退火条件，后以2-300 C/h冷却。(1)第二阶段条件为602ºC和100h，得到f2型冷却速度高于200ºC/h，而f2m型冷却速度较慢。(2)在200ºC/h的冷却速率下，无二次淬火，得到f2型淬火温度高于728ºC，而f2m型淬火温度低于676ºC。第二阶段条件为708-728℃，5-282h，得到f2型。(3)在200ºC/h的冷却速率和739ºC/ 41ºh的第二阶段冷却条件下，得到f2m型。我们有以下临时的实验结果。从这样的实验结果来看，f2m型似乎是一个较低的相位。认为f2m型二十面体相的实现需要两个过程：第一个过程是f型到f2型相变，这个过程完成的时间很短；第二种是f2型到f2m型相变，这被认为是一个扩散过程，因为这需要很长时间。现在我们要做mm单f2m型二十面体准晶体我们有x射线衍射实验。少

The main aim of this research is to study the quasicrystal-quasicrystal phase transformation of Al-Pd-Mn icosahedral phase. It have been reported that an Al_<71>Pd_<21>Mn_8 icosahedral phase is not only an F-type icosahedral phase, but can be F2-type and F2M-type icosahedral phases. We have added to study F2M-type phase. On the alloy composition near Al_<71>Pd_<21>Mn_8, the F-type icosahedral phase is stable at about 800ﾟC,whose name is originated as the 6-dim supercubic lattice based on the idea is face centered cubic. The F2-type is understood and F2M-type icosahedral phases. We have added to study F2M-type phase. It is easy to understood the F2M-type as the 6-dim diamond lattice of F2-type icosahedral phase. We have tryed to study the feature of unknown F2M-type icosahedral phase, we called medium phase, and the growing conditions of F2-type and F2M-type icosahedral phases. And We have got the knowledge for the quasicrystal stability.Feature of unknown F2M-type icosahedral phase : F … More 2M-type is not truely icosahedral phase, but has trigonal or cubic symmetry. It has usual crystal symmety, but quasiperiodic.Growing conditions of F2-type and F2M-type icosahedral phases : We searched it under such conditions ; we fixed the higher temperature annealing condition as T=803-806ﾟC and 50 hours and we controlled the second annealing conditions, cooling it by 2-300ﾟC/h after it. (1) As the result of the second stage condition as 602ﾟC and 100h, we got F2-type as the higher cooling rate than 200ﾟC/h and F2M-type as slower. (2) As the result of the 200ﾟC/h cooling rate and no second stage, we got F2-type as the higher quenching temperature than 728ﾟC and F2M-type as lower than 676ﾟC.As the result of the second stage condition as 708-728ﾟC and 5-282h, we got F2-type. (3) As the result of the 200ﾟC/h cooling rate and the second stage condition as 739ﾟC and 41h, we got F2M-type.We have the temporary following experimental results. It seems to be true from such experimental results that the F2M-type is a lower phase. It is thought that the realization of F2M-type icosahedral phase needss to two processe : The first process is F-type to F2-type phase transformation and this finishes for a short time ; The second is F2-type to F2M-type phase transformation and this is thought to be a diffusion process as this needs for a long time. Now we are going to make mm single F2M-type icosahedral phase quasicrystals as we have x-ray diffraction experiments. Less