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

本文主要研究Al-Pd-Mn二十面体相的准晶-准晶相变。Al_<71>Pd_Mn_8<21>二十面体相不仅是F型二十面体相，而且可以是F_2型和F_2M型二十面体相。我们增加了对F2 M型相的研究。在Al_Pd_Mn_8附近的合金成分中<71><21>，F型二十面体相在800 ℃左右是稳定的，其名称来源于基于面心立方思想的六维超立方晶格。F2型被理解为F2 M型二十面体相。我们增加了对F2 M型相的研究。F2 M型很容易理解为F2型二十面体相的六维金刚石晶格。本文试图研究未知的F_2M型二十面体相（我们称之为中间相）的特征，以及F_2型和F_2M型二十面体相的生长条件。并对准晶的稳定性有了认识。未知F2 M型二十面体相的特征：F ...更多信息 2 M型不是真正的二十面体相，而是三方或立方对称。F_2型和F_2M型二十面体相的生长条件：在此条件下进行了探索;确定高温退火条件为T=803-806 ℃，50小时，并控制二次退火条件，（1）在602 ℃、100 h的第二阶段条件下，得到了冷却速度大于200 ℃/h的F_2型和冷却速度较慢的F_2M型。(2)由于冷却速度为200 ℃/h，没有第二阶段，所以淬火温度高于728 ℃时为F2型，淬火温度低于676 ℃时为F2 M型。由于第二阶段条件为708-728 ℃，5- 282小时，所以为F2型。(3)在冷却速度为200 ℃/h，第二阶段冷却条件为739 ℃，41小时的条件下，得到了F2 M型的冷却结构。从这样的实验结果看来，F2 M型是较低的相似乎是正确的。认为F2 M型二十面体相的实现需要经历两个过程：第一个过程是F型到F2型的相变，这一过程完成的时间较短;第二个过程是F2型到F2 M型的相变，这一过程需要较长的时间，这被认为是一个扩散过程。现在我们要做mm的F2 M型二十面体相准晶，因为我们有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