非规则共晶小平面相失稳及其层片间距研究

Irregular eutectic involves various commonly used industrial alloy and developing high performance advanced material, including steel, nonferrous metal, ultrahigh temperature in situ composite and high temperature superconductor. Its microstructure morphology and characteristic scales are the determinants on the material performance. The key factors for researching the characteristic scales of the irregular eutectic are the exploration of the orientation characterization of the facet phase destabilization and the solution field of the non-isothermal solid-liquid interface. This project uses the Bridgman directional solidification as the major researching method. The typical irregular eutectic (Al-Si) is chosen as the study objects. The seed crystal is used to tightly control the growth orientation of the irregular eutectic. The orientation characterization of the facet phase destabilization is investigated with various seed crystal orientation and solidification rate. The spatial distribution of the facet phase is 3D restructured. The solution distribution under non-isothermal interface is proven and mathematical proofed by the finite difference. The destabilization of the facet phase is systematically analyzed by the phase field method combining the orientation characterization and the solution distribution. Finally, the formation mechanism of the irregular eutectic characteristic scales is revealed exactly. Based on the study of this project, this fundamental scientific problem on the eutectic solidification will be solved.

非规则共晶凝固涉及了包括钢铁、有色金属，超高温自生复合材料以及高温超导体等多种常用的工业合金以及在研的先进高性能材料，其层片间距是材料性能的决定因素。研究非规则共晶层片间距的关键在于探究小平面相在共晶耦合生长过程中失稳的取向特征以及非等温界面溶质场。本项目拟采用Bridgman定向凝固方法作为主要研究手段，以Al-Si典型非规则共晶为研究对象，并利用籽晶法严格控制非规则共晶生长取向，考察不同生长取向及凝固速率条件下小平面相失稳的取向特征，并对小平面相空间分布状态进行三维重构。探明非等温界面条件下的溶质分布特征，并利用有限差分方法进行数学佐证。结合小平面相的晶体学特征以及溶质场数据利用相场法对小平面相失稳进行统一分析。以期揭示非规则共晶层片间距演化规律，通过本项目研究解决这一共晶凝固基础科学问题。

大多数常用的工业合金以及在研的先进高性能材料的制备及特种冶金加工技术都涉及到了非规则共晶凝固过程，理解和把握非规则共晶材料体系在凝固过程中组织形成和演化行为对于指导生产实践，提升和优化材料性能就显得极为重要。项目致力于探究非规则共晶特征尺度的形成机制，解决目前非规则共晶生长研究中涉及小平面相失稳行为方面的佯谬，为建立完善的共晶生长理论，促进共晶凝固加工技术的发展奠定坚实的科学基础。