Microstructural Evolution in Sintering - Experimental, Mathematical and Numerical Study

该项目研究了材料科学中的一个重要过程——粉末的固态烧结。为了理解、控制和预测烧结过程的结果，需要从微观结构的角度对烧结过程进行仔细的研究。该项目旨在基于特定烧结和相关机制的过程模拟，而不是经验，统计功能。为了从机制的角度模拟烧结，研究人员采用了实验、数学模型和数值模拟的结合。在众多烧结机制中，研究人员选择了一种经常主导烧结过程的常见机制——晶界扩散。它们将表面传质和晶界扩散耦合在一起，形成一个完整的数学系统。该系统涉及高阶非线性偏微分方程和移动边界。为了解决这个系统，研究人员使用了一种精确有效的数值方法来求解偏微分方程，结合了区域分解和自适应/移动网格。探讨了细粒度级和粗粒度级仿真算法的并行计算。为了验证和证实仿真，本项目设计并进行了八个实验。其中七个目标是粒子的简单规则几何形状。由于实验的原因，在大多数实验中都使用了镀镍W线。这些实验与基于个体机制的数学模型提供了良好的比较。实验结果将与数值模拟结果进行比较。这些比较将验证和估计理论模型的有效性。在这些简单案例的基础上进行比较后，研究人员将进行一个涉及多种机制和耦合的不规则颗粒簇的烧结实验。该实验结果将与扩大的完整数学系统的数值模拟结果进行比较。本研究为研究烧结对烧结材料微观结构演变的影响提供了有力的工具。通过实验、数学模型和计算机模拟相结合，研究结果将更接近真实世界的情况，更好地解释烧结过程中的微观组织演变。模拟将有助于科学家和工程师更好地了解烧结材料的性能，并优化烧结工艺。＊＊＊

9705849 Zhang The project investigates an important process in materials science, solid state sintering of powders. In order to understand, control and predict the results of a sintering process, a close study of the process from a microstructural point of view is required. This project aims at process simulations based on specific sintering and related mechanisms rather than empirical, statistical functions. To model sintering from the mechanism point of view, the investigators employ a combination of experiments, mathematical models, and numerical simulations. Among many sintering mechanisms, the investigators have selected a common one which often dominates the sintering process, grain boundary diffusion. They couple mass transport by surface and grain boundary diffusion to form a complete mathematical system. This system involves high order nonlinear partial differential equations (PDEs) and moving boundaries. To solve this system, the investigators use an accurate and efficient numerical method for solving PDEs, combined with domain decomposition and adaptive/moving grids. A parallel computation in the simulation algorithm for both fine and coarse granularity level is also explored. To verify and corroborate the simulation, the project designs and carries out eight experiments. Seven of these target simple regular geometries of particles. For experimental reasons, Ni-coated W wires are used in most of the experiments. These experiments provide sound comparisons with the mathematical models based on individual mechanisms. The experimental results will be compared with the numerical simulations. These comparisons will verify and estimate the validity of the theoretical models. After comparisons based on these simple cases, the investigators will conduct an experiment on the sintering of an irregular cluster of particles where several mechanisms are involved and coupled. This experimental result will be compared with the numerical simulation of the enlarged complete mathematical system. %%% This investigation provides a powerful tool for studying the effects of sintering on the evolution of the microstructure of a sintering material. By combining experiments, mathematical models and computer simulations, the results will closely follow real world situations and better explain the microstructural evolution during sintering. The simulation will help scientists and engineers to understand better the properties of the sintered materials and to optimize sintering process. ***