Study of massive transformation using diffusion couples of multicomponent alloys for CALPHAD consistent modeling of interface controlled phase transformations

使用多元合金扩散偶进行大规模相变研究，用于界面控制相变的 CALPHAD 一致建模

• 批准号: 314528341
• 负责人: Dr.-Ing. Stephanie Lippmann
• 金额: --
• 依托单位: Otto-Schott-Institut für Materialforschung (OSIM)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/314528341?language=en
• 关键词: Study; massive; transformation; using; diffusion

In the proposed project the influence of the thermodynamic state of the interface during solid state phase transformations will be investigated on the example of massive transformation. Massive transformation is an at least partially interface controlled transformation. Controversially discussed questions are i) to what degree the interface between parent and product phase is in thermodynamic equilibrium and ii) if a concentration spike forms in the parent phase in front of the migration interface.The goal of the proposal is the characterization of the transition between interface and diffusion controlled phase transformation in multicomponent systems for providing a general criterion for this transition, as e.g. needed for mesoscopic modeling. The combination of experimental results and simulation calculations using a thermodynamic and kinetic model considering interface thermodynamics (i.e. processes at the interface in local equilibrium or deviations thereof) will allow the quantification of the energy dissipation at the interface and thus enhance the quantitative understanding of interface controlled phase transformations.For a characterization of the transition from massive to diffusion controlled phase transformations, the transformation rate will be varied by the process conditions (heating or cooling rate) and adding ternary alloying elements. Diffusion couples on the basis of the binary Ag-Zn and Cu-Zn systems will be used. After the preparation of a distinct concentration gradient, a broad range of local concentrations can be observed within a single sample.Heating is realized by pulse heating a wire with electric current. For fast and variable temperature control that allows the heating, holding, cooling and cycling around a chosen temperature a state-of-the-art photon detector camera will be employed. The camera will control the temperature along the entire sample in spatially and temporally highest possible resolution. After FIB lamella preparation the concentration distribution around the transformation front will be investigated using high resolution transmission electron microscopy in combination with energy dispersive X-ray spectroscopy.

在拟议的项目中，将以大量相变为例研究固态相变过程中界面热力学状态的影响。大规模转变是至少部分界面控制的转变。有争议的讨论问题是 i) 母相和产物相之间的界面处于热力学平衡的程度，以及 ii) 迁移界面前面的母相中是否形成浓度峰值。该提案的目标是表征转变多组分系统中界面和扩散控制相变之间的关系，为这种转变提供一般标准，例如介观建模所需。使用考虑界面热力学（即界面处的局部平衡或其偏差的过程）的热力学和动力学模型将实验结果与模拟计算相结合，将能够量化界面处的能量耗散，从而增强对界面控制的定量理解相变。为了表征从块状相变到扩散控制相变的转变，转变速率将根据工艺条件（加热或冷却速率）和添加三元合金元素而变化。将使用基于二元银-锌和铜-锌系统的扩散偶。制备出明显的浓度梯度后，可以在单个样品内观察到广泛的局部浓度。加热是通过用电流脉冲加热金属丝来实现的。为了实现快速和可变的温度控制，允许加热、保持、冷却和围绕选定温度循环，将采用最先进的光子探测器相机。相机将以空间和时间上尽可能高的分辨率控制整个样品的温度。 FIB 薄片制备后，将使用高分辨率透射电子显微镜结合能量色散 X 射线光谱来研究转换前沿周围的浓度分布。