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Crystal growth velocity in deeply undercooled melts of glass forming Zr-based alloys

玻璃形成锆基合金深过冷熔体中的晶体生长速度

基本信息

批准号：
238485687
负责人：
Professor Dr. Dieter M. Herlach (†)
金额：
--
依托单位：
Institut für Experimentalphysik IV: Lehrstuhl für Festkörperphysik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2013
资助国家：
德国
起止时间：
2012-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/238485687?language=en
关键词：
Crystal growth velocity deeply undercooled

项目摘要

The corporate goal is to investigate the solidification of glass-forming materials through both, experiments and phase-field simulations. At higher undercoolings, diffusion gets limited in materials forming glasses. This leads to a non-monotonic behavior of the velocity as a function of undercooling. To understand this, we consider Zr-based alloys as they can be cooled in the vicinity of the glass transition temperature in a levitation setup. We treat both, binary and multi-component alloys, and establish the solidification paths and kinetics. The experimentalists evaluate composition profiles as well as the crystal growth velocities at different undercoolings and provide the data for validation of the developed quantitative phase-field model for solidifications at higher undercoolings involving effects of solute trapping and partitionless phase transition. The phase-field model is further used to investigate pattern formations in glass-forming systems and to characterize the morphologies obtained at different undercoolings. The observed microstructures and velocity-undercooling relations are correlated to those for non-glass forming materials and the differences will be theoretically researched. The geometrical characteristics of the microstructures, such as dendritic tip radii and eutectic lamellae spacings are compared with experiments and with analytical theories, the corresponding discrepancies are analyzed and appropriate corrections to the theoretical models for glass forming materials are discussed. We study morphological transitions from dendritic to eutectic microstructures and determine the onset of these transitions as a function of undercooling and off-eutectic compositions. The overall aim is to explore the kinetics, solidification and topology paths of glass forming alloys under extreme conditions.

公司的目标是通过实验和相场模拟来研究玻璃成形材料的凝固。在较高的过冷度下，玻璃材料的扩散受到限制。这导致了速度作为过冷函数的非单调行为。为了理解这一点，我们考虑了锆基合金，因为它们可以在悬浮设置中在玻璃化转变温度附近冷却。我们处理了二元合金和多组分合金，并建立了凝固路径和动力学。实验人员评估了不同过冷度下的成分分布和晶体生长速度，并为高过冷度下溶质捕获和无分割相变影响的凝固定量相场模型的验证提供了数据。相场模型进一步用于研究玻璃形成系统中的图案形成，并表征在不同过冷条件下获得的形貌。观察到的显微组织和速度-过冷关系与非玻璃形成材料的相关，并将从理论上研究其差异。将枝晶尖端半径和共晶片间距等微观结构的几何特征与实验和分析理论进行了比较，分析了相应的差异，并讨论了对玻璃成形材料理论模型的适当修正。我们研究了从枝晶到共晶微观结构的形态转变，并确定了这些转变的开始作为过冷和非共晶成分的函数。总体目标是探索极端条件下玻璃成形合金的动力学、凝固和拓扑路径。