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，将用常规的静态显微照片由于速度快而不能完全跟踪的各种合金系的一级相变过程记录在录像带上，并用计算机图像处理对所得数据进行分析。结果如下：1. Fe-30at%Pd合金的bcc（bct）马氏体宏观形态是在原有马氏体晶界处为获得相容性而自适应的变体晶体排列. Fe-30at%Pd合金bcc（bct）马氏体中的特征斑衬与奥氏体中Pd原子的部分聚集引起的应变衬和孪晶引起的晶格不变应变有关. Fe-30at%Pd合金从奥氏体到fct的热弹性马氏体相变表现出从粗花呢到微孪晶的特征性介观尺度对比度变化。高分辨率电子显微镜的图像处理 ...更多信息 粗花呢的显微照片表明，变形区和未变形区形成平行于{011}面的交替层，变形区含有四边形变形的静应变中心.在FePd合金有序化的早期阶段，具有介观尺度的应变对比对应于系统的动力学平衡和化学平衡之间的竞争状态.用超高压电子显微镜原位观测了Ni和Au合金辐射诱导二次缺陷和沉淀物形成的温度依赖性。确定了溶质与辐照形成的点缺陷的相互作用能，并讨论了溶质浓度随辐照涨落的对比度随时间的变化.原位观察等原子FeRh合金的一级相变，清楚地表明铁磁和反铁磁相的边界随温度的变化而移动。1000 K退火时相变过程的变化是由细小的析出物引起的，而这些析出物的形成至今还不能用相图来解释。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