Kinetics of Formation of Mesoscopic Scale Patterns in First Order Phase Transition of Alloys

在透射电子显微镜上安装了高灵敏度的CCD摄像机，将各种合金系统的一级相变过程记录在录像带上，这些过程由于速度快，用常规的静态显微照片无法完全跟踪，并用计算机图像处理对数据进行了分析。研究结果如下：1.研究结果如下：Fe-30at%Pd合金的体心立方(Bct)马氏体的宏观形态是通过自适应在原有奥氏体晶界上实现相容而形成的各种晶体的排列。Fe-30at%Pd合金体心立方(BCT)马氏体中的特征斑驳对比度与奥氏体中Pd原子的局部聚集和孪晶晶格不变应变的应变对比度有关。Fe-30at%Pd合金从奥氏体热弹性马氏体相变到FCT马氏体相变呈现出从花纹到微孪晶的特征介观对比度变化。高分辨率电子…的图像处理更多的花呢显微照片表明，扭曲和未扭曲的区域形成了平行于{011}面的交替层，并且扭曲的区域包含四方扭曲的静态应变中心。在FEPD合金有序化的早期阶段，应变与介观尺度的对比反映了体系的动力学平衡和化学平衡之间的竞争状态。通过超高压电子显微镜的原位观察，测量了Ni和Au合金中辐照诱导的二次缺陷和析出物形成的温度依赖性。测定了溶质与辐射形成的点缺陷的相互作用能，讨论了辐射引起的溶质浓度随时间的变化规律。对等原子FeRh合金的一级相变进行了原位观察，清楚地显示了铁磁和反铁磁相的晶界随温度的变化。1000K时相变过程随退火温度的变化是由细小的析出物引起的，到目前为止还没有用相图来解释。较少

A high sensitive CCD video camera was installed in a transmission electron microscope,and processes of first order phase transition of various alloy systems which are not fully traced by taking conventional still micrographs because of the quickness are recorded on video-tapes,and the data obtained are analyzed by computer image processing. The results are in the following.1. Macroscopic patterns of bcc(bct) martensite of Fe-30at%Pd alloy are arrangements of variant crystals due to self-accommodation to attain compatibility at grain boundaries of the pre-existing austenite.2. Characteristic mottled contrast in bcc(bct) martensite of Fe-30at%Pd alloys is associated with strain contrast by partial clustering of Pd atoms in the austenite and lattice invariant strain by twinning.3. Thermoelastic martensite transformation from austenite to fct of an Fe-30at%Pd alloy exhibit a characteristic mesoscopic scale contrast change from tweed to microtwins. Image processing of high resolution electr … More on micrographs of tweed indicates that distorted and undistorted regions form altemating layers parallel to {011} planes, and the distorted regions contain tetragonaly distorted static strain centers.4. Strain contrast with a mesoscopic scale in an early stage of ordering of FePd alloys corresponds to a competing state between dynamical and chemical equilibrium of the system.5. Temperature dependence of formation of radiation induced secondary defects and precipitates of Ni and Au alloys is measured by in-situ observations of an ultra high voltage electron microscope. Interaction energies of solutes with radiation formed point defects are determined,and the contrast change with elapse of times is discussed on the fluctuation of solute concentration with irradiation.6. In-situ observation of first order phase transition of an equi-atomic FeRh alloy clearly shows movements of boundaries of ferromagnetic and antiferromagnetic phases with change in temperature. The variation of transition process with annealing at 1000K is originated from fine precipitates,the formation of which is not explained by phase diagrams so far. Less