Study of the fundamental role of interfacial mobilities during phase transformations in aluminium alloys

铝合金相变过程中界面迁移率基本作用的研究

• 批准号: RGPIN-2018-04530
• 负责人: Larouche, Daniel
• 金额: $ 2.84万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=687441
• 关键词: Study; fundamental; role; interfacial; mobilities

This research program is dedicated to the study precipitation hardening in Aluminium alloys from the phenomena occurring at the interface of precipitates, which regulate the interfacial mobility and so the growth rate during the early stage of precipitation. The concept of interfacial mobility was used to explain grain growth and massive transformations because there is no concentration gradient involved in these transformations. These transformations are said to be being interface controlled. In the last decade, some authors stated that the early stage of solid-state precipitation is also interface controlled, the interface being out of equilibrium during that stage. This implies that a precise estimation of the growth rate at the beginning of the transformation requires to know the value of the interfacial mobility. The problem is that there were no data for the interfacial mobility of precipitates until we have developed recently a methodology for its evaluation and its temperature dependency from the heat measured by a differential scanning calorimeter (DSC) and image analysis of pictures taken in a transmission electron microscope (TEM). The new method was applied on a binary Aluminium alloy. Now, we want to evaluate the influence of chemical composition on the interfacial mobility of precipitates and we will try to find what elements can be added in very small amounts in the matrix while impacting strongly the interfacial mobility. We hope to find compositions enhancing the stability of the microstructure of Aluminium alloys at elevated temperatures. This part of the research program will be conducted by a PhD candidate.*******Hardness is not only determined by the size of the precipitates but also on the number of precipitates per unit volume, called hereafter number density. We intend to study the evolution of number density during all stages of precipitation. A set of experiments is proposed where alloys aged under different conditions will be submitted to TEM examinations to estimate the number density at specific times of aging. The evolution of number density is well recognized in the literature, particularly during the coarsening stage, but actual measurements are scarce because of the costs associated to sample preparation and TEM examinations. The price is worthy only for those who are motivated to develop a complete microstructure model able to predict the hardness. With the growth and dissolution model we have developed recently for multicomponent precipitates, which includes the interfacial mobility as an important parameter, the measurements of the evolution of the number density will help us to assess the nucleation and coarsening models that will eventually be added to the actual growth and dissolution model. The experimental determination of the number densities would be conducted by a MSc candidate, while the nucleation and coarsening models will by developed by two PhD candidates.***

该研究项目致力于从沉淀物界面发生的现象研究铝合金中的沉淀硬化，这种现象调节界面流动性，从而调节沉淀早期的生长速率。界面迁移率的概念用于解释晶粒生长和大规模转变，因为这些转变中不涉及浓度梯度。这些转换据说是由接口控制的。在过去的十年中，一些作者指出，固态沉淀的早期阶段也是界面控制的，界面在该阶段失去平衡。这意味着在转变开始时精确估计增长率需要知道界面迁移率的值。问题是，在我们最近开发了一种评估方法及其温度依赖性（通过差示扫描量热计（DSC）测量的热量和对透射电子显微镜（TEM）拍摄的图像进行图像分析）之前，没有关于沉淀物界面迁移率的数据。新方法应用于二元铝合金。现在，我们想要评估化学成分对沉淀物界面迁移率的影响，我们将尝试找出哪些元素可以在基体中添加非常少量的元素，同时强烈影响界面迁移率。我们希望找到增强铝合金微观结构在高温下稳定性的成分。这部分研究计划将由一名博士生进行。********硬度不仅取决于沉淀物的大小，还取决于每单位体积沉淀物的数量（以下称为数密度）。我们打算研究降水各个阶段的数量密度的演变。提出了一组实验，其中将在不同条件下老化的合金进行 TEM 检查，以估计特定老化时间的数密度。数密度的演变在文献中得到了充分认可，特别是在粗化阶段，但由于与样品制备和 TEM 检查相关的成本，实际测量很少。仅对于那些有动力开发能够预测硬度的完整微观结构模型的人来说，这个价格才值得。通过我们最近开发的多组分沉淀物的生长和溶解模型（其中包括界面迁移率作为重要参数），数密度演变的测量将帮助我们评估最终将添加到实际生长和溶解模型中的成核和粗化模型。数密度的实验测定将由一名理学硕士候选人进行，而成核和粗化模型将由两名博士候选人开发。***