EAGER: An Innovative Modelling Approach to Predict Non-Equilibrium Phases Produced in Metal Additive Manufacture Processes

这个早期概念探索性研究（EAGER）项目将开发一种新的未经测试的方法来模拟复杂金属合金的原子排列演变的非平衡行为。在金属的增材制造中，使用各种工艺图来指导时间和温度的选择，以产生所需的微观结构，以满足所需的机械性能或性能。大多数金属制造过程在已知的温度和时间条件下处于平衡状态。相比之下，激光工程的净成形和相关的增材制造工艺通过将金属沉积为小的熔融滴来制造零件，这些熔融滴被快速反复加热并一层一层地凝固。虽然这大大减少了直接构建复杂的多部件组装的时间、成本和重量，但增材制造中快速重复的熔化和再凝固会导致各种难以预测的非平衡相，从而导致最终的微观结构和机械性能的不确定性。目前，昂贵的试错实验研究构成了这种微观结构发展的基础。这项工作有可能实现非平衡图，从而实现增材制造的全部潜力，从而推进工业上重要合金的加工，从而赋予生物医学、航空航天、化学和能源行业的新应用。因此，这项工作将增强美国经济、社会和全球制造业的竞争力。为了充分发挥增材制造降低制造成本的潜力，需要生成可行的热力学和动力学路线图来预测微观结构，以指导和优化加工参数，从而优化材料性能。镍基高温合金Inconel 718的热力学和动力学将从第一性原理计算和数据密集的统计力学方法中建模。原子排列在给定温度和化学势下的时间演化将基于空位扩散机制进行建模。原子构型的变化将在绝热近似下模拟，在跳跃时间尺度上平均出电子和晶格振动等快速自由度。然后，原子排列的时间演化将通过一系列事件来建模：将一个空位与其最近的一个原子交换，这相当于被交换的原子跳到空的位置。将数值预测与实验观察到的微观结构响应相结合将迅速验证所提出的方法。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This EArly-concept Grant for Exploratory Research (EAGER) project will develop a new and untested approach toward modeling of the non-equilibrium behavior of complex metal alloys in terms of the evolution of their atomic arrangement. In additive manufacturing of metals, various process maps are used to guide the selection of time and temperature to produce the desired microstructure to meet the required mechanical properties or performance. Most metal fabrication processes occur at equilibrium, with known conditions of temperature and time. In contrast, the laser-engineered net shaping and related additive manufacturing processes builds a part by depositing the metal as small molten drops which are rapidly and repeatedly heated and solidified layer by layer. While this greatly reduces the time, cost, and weight in the direct build of a complex multi-part assembly, the rapid and repeated melting and re-solidification in additive manufacturing results in a variety of difficult-to-predict non-equilibrium phases that lead to uncertainty in the resulting microstructure and mechanical properties. At present, expensive trial-and-error experimental studies form the basis for such microstructural development. This work has the potential to realize non-equilibrium maps that will enable the full potential of additive manufacturing, thereby advancing the processing of industrially significant alloys to empower new applications in the biomedical, aerospace, chemical, and energy industries. As a result, this work will enhance the US economy, society, and global competitiveness in manufacturing. To realize the full potential for reducing fabrication costs through the use of additive manufacturing, viable thermodynamic and kinetic road maps need to be generated for predicting the microstructures to guide and optimize the processing parameters to optimize the material performance. The thermodynamics and kinetics of Inconel 718, a nickel based superalloy, will be modeled from first-principles calculations and data-intensive statistical mechanics approaches. The temporal evolution of atomic arrangements at given temperature and chemical potentials, will be modeled based on the diffusion through vacancy mechanism. The change of atomic configuration will be simulated under an adiabatic approximation, averaging out fast degrees of freedom such as electronic and lattice vibrations on the hopping time scale. Then, the temporal evolution of atomic arrangement will be modeled by a series of events: switching a vacancy with one of its nearest neighbor atoms, which is equivalent to the hopping of the switched atom to the vacant site. Integrating numerical predictions with experimentally observed microstructural responses will rapidly verify the proposed approach.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.