Elder Kate L M, Andrews W Beck, Ziehmer Markus, Mameka Nadiia, Kirchlechner Christoph, Davydok Anton, Micha Jean-Sébastien, Chadwick Alexander F, Lilleodden Erica T, Thornton Katsuyo, Voorhees Peter W
Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208.
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109.
Proc Natl Acad Sci U S A. 2021 Jul 27;118(30). doi: 10.1073/pnas.2104132118.
Grain boundary formation during coarsening of nanoporous gold (NPG) is investigated wherein a nanocrystalline structure can form by particles detaching and reattaching to the structure. MicroLaue and electron backscatter diffraction measurements demonstrate that an in-grain orientation spread develops as NPG is coarsened. The volume fraction of the NPG sample is near the limit of bicontinuity, at which simulations predict that a bicontinuous structure begins to fragment into independent particles during coarsening. Phase-field simulations of coarsening using a computationally generated structure with a volume fraction near the limit of bicontinuity are used to model particle detachment rates. This model is tested by using the measured NPG structure as an initial condition in the phase-field simulations. We predict that up to ∼5% of the NPG structure detaches as a dealloyed [Formula: see text] sample is annealed at 300 °C for 420 min. The quantity of volume detached is found to be highly dependent on the volume fraction and volume fraction homogeneity of the nanostructure. As the void phase in the experiments cannot support independent particles, they must fall and reattach to the structure, a process that results in the formation of new grain boundaries. This particle reattachment process, along with other classic processes, leads to the formation of grain boundaries during coarsening in nanoporous metals. The formation of grain boundaries can impact a variety of applications, including mechanical strengthening; thus, the consideration and understanding of particle detachment phenomena are essential when studying nanoporous metals.
研究了纳米多孔金（NPG）粗化过程中的晶界形成，其中纳米晶体结构可通过颗粒脱离并重新附着到该结构上而形成。微劳厄和电子背散射衍射测量表明，随着NPG粗化，晶粒内取向差会增大。NPG样品的体积分数接近双连续极限，在该极限下，模拟预测双连续结构在粗化过程中开始破碎成独立颗粒。使用具有接近双连续极限体积分数的计算生成结构进行粗化的相场模拟，以模拟颗粒脱离速率。通过将相场模拟中测量的NPG结构用作初始条件来测试该模型。我们预测，当脱合金化的[化学式：见原文]样品在300℃退火420分钟时，高达约5%的NPG结构会脱离。发现脱离的体积量高度依赖于纳米结构的体积分数和体积分数均匀性。由于实验中的孔隙相无法支撑独立颗粒，它们必须掉落并重新附着到结构上，这一过程导致新晶界的形成。这种颗粒重新附着过程，以及其他经典过程，导致纳米多孔金属在粗化过程中形成晶界。晶界的形成会影响包括机械强化在内的各种应用；因此，在研究纳米多孔金属时，考虑和理解颗粒脱离现象至关重要。
