CAREER: Mesoscopic Scale Phase Separation in Alloys under Sustained External Forcing

小行星9733582 这个职业资助解决了以材料的非平衡处理为中心的研究和教育计划。 研究部分审查了新的想法，即在合金中，在持续的外力作用下，相分离可能发生在介观尺度上，即既不是原子尺度，也不是宏观尺度，这些介观结构可以在稳态下稳定。本研究的主要目的是：（a）在受控条件下通过球磨对具有正混合热的合金在稳态下的成分场进行详细的表征：（B）阐明在持续剪切下合金介观相分离稳定化的起源;以及（c）测试关于这些介观结构的现有实验结果是否可以通过具有竞争动力学的动力学模型来合理化，其中位错滑移将是迫使不混溶元素混合的动力学。 所选择的方法涉及在受控条件下研磨Fe-Cu和Cu-Ag粉末，并使用可以解决纳米组成异质性的分析技术，包括首次使用原子探针和三维原子探针技术对球磨材料进行分析。 原子计算机模拟和建模应该有助于理解这些受迫系统。 该建议的教育部分包括利用CyberProf（Urbana的Beckman研究所开发的一种人机界面）为关于辐照下材料的研究生课程编写一份计算机辅助材料;以及重组一个本科材料科学实验室，以激发学生的主动性。 最近通过原子计算机模拟在具有正混合热的金属合金中发现了介观相分离。 这些发现与最新发表的实验结果一致，实验结果表明，球磨时，具有正混合热的合金具有复杂的动力学相平衡和强烈的化学不均匀性。 非平衡系统领域在过去的二十年里得到了迅速的发展和广泛的关注，这是本研究的动机。 实际上，在许多应用中，材料在其制备期间（例如，通过球磨）或在它们的使用过程中（例如，通过辐射）。 ***

9733582 Bellon This CAREER grant addresses research and educational programs which are centered on non-equilibrium processing of materials. The research component examines the new idea that in alloys under sustained external forcing phase separation may take place on a mesoscopic scale, i.e. a scale which is neither atomic, nor macroscopic, and these meso-structures can be stable at steady-state. The objectives of the proposed research are: (a) to perform a detailed characterization of the composition field in alloys with positive heat of mixing at steady-state during by ball milling under controlled conditions; (b) to elucidate the origin of the stabilization of mesoscopic phase separation in alloys under sustained shearing; and (c) to test whether the available experimental results on these mesostructures can be rationalized by a kinetic model with competing dynamics, where dislocation glide would be the dynamics forcing the mixing of immiscible elements. The approach chosen involves the milling of Fe-Cu and Cu-Ag powders under controlled conditions and the use of analytical techniques that can resolve nanometric composition heterogeneity, including for the first time for ball milled materials the use of atom probe and three-dimensional atom probe techniques. Atomistic computer simulations and modeling should assist in understanding of these forced systems. The educational component of the proposal consists in developing a computer-assisted material for a graduate course on materials under irradiation using CyberProf, a human- computer interface developed at the Beckman Institute in Urbana; and in reorganizing an undergraduate materials science laboratory to stimulate initiatives from the students. %%% Mesoscopic phase separations have been recently identified in metal alloys with positive heats of mixing under sustained shearing by atomistic computer simulations. These findings are consistent with the latest published experiments showing complex dy namical phase equilibria and strong chemical heterogeneity in alloys with positive heat of mixing when submitted to ball milling. This research is motivated by the fact that the field of nonequilibrium systems is in rapid development and has received much attention in the last two decades. Indeed in many applications, materials are driven away from equilibrium by some external forcing, either during their preparation (e.g., by ball milling) or during their use (e.g., by irradiation). ***