Multi-scale analysis of omega transformation using novel microscopy techniques

本文研究了β-钛、锆合金欧米伽相变过程中尚未解决的五个问题：非热相和等温相的结晶学差异、非热相和等温相的实量纲分析、冶金因素对相形态和结晶学的影响、相变机制以及欧米伽相变与热弹马氏体相变前驱现象之间的关系。我们成功地用高角度环状暗场扫描电子显微镜直接观察到了非热和等温欧米伽相的哑铃结构特征原子排列。对哑铃结构中原子的相对位移进行了定量估算。位移量从omega内区的0.5逐渐增加到omega/beta界面的0.67。在三维层析成像的基础上，讨论了相变机制与各种omega形貌的关系。

Following five unsolved problems in omega transformation in beta-Ti and Zr alloys were investigated; crystallographic difference between athermal and isothermal phases, real dimensional analysis of athermal and isothermal phases, effect of metallurgical factors on morphology and crystallography, transformation mechanism and relation between omega transformation and precursor phenomena of thermoelasticmartensi tic transformation.We succeeded in direct observation of the characteristic atomic arrangement with dumbbell structure in athermal and isothermal omega- phases beta-Ti and Zr alloys by high-angleannular dark field scanning transmission electron microscopy. The relative atomic displacement in the dumbbell structure was quantitatively estimated. The displacement gradually increased from 0.5 at the inner region of omega to 0.67 at omega/beta interface. The relation between transformation mechanism and each of omega morphologies has been also discussed on the basis of 3D tomography.