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

职业：持续外力作用下合金中的细观尺度相分离

• 批准号: 9733582
• 负责人: Pascal Bellon
• 金额: $ 30万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-05-01 至 2003-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9733582&HistoricalAwards=false
• 关键词: CAREER; Mesoscopic; Scale; Phase; Separation

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). ***

9733582贝隆这项职业助学金针对的是以材料的非平衡加工为中心的研究和教育项目。该研究部分检验了一种新的观点，即在持续的外力作用下，合金中的相分离可能发生在介观尺度上，即既不是原子的，也不是宏观的，并且这些介观结构可以在稳定状态下稳定。这项研究的目的是：(A)详细描述在可控条件下球磨过程中具有正混合热的合金的成分场；(B)阐明合金在持续剪切下介观相分离稳定的原因；以及(C)检验关于这些细观结构的现有实验结果是否可以用具有竞争动力学的动力学模型来解释，其中位错滑移将是迫使不相容元素混合的动力学。选择的方法包括在受控条件下球磨Fe-Cu和Cu-Ag粉末，并使用可以解决纳米成分不均质性的分析技术，包括首次对球磨材料使用原子探针和三维原子探针技术。原子化的计算机模拟和建模应该有助于理解这些强迫系统。该提案的教育部分包括使用CyberProf(位于乌尔巴纳的Beckman研究所开发的人机界面)为关于辐照材料的研究生课程开发计算机辅助材料；以及重组本科生材料科学实验室，以激发学生的积极性。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持续剪切下的介观相分离。这些发现与最新发表的实验结果一致，这些实验表明，在球磨时，具有正混合热的合金中存在复杂的动力学相平衡和强烈的化学不均质性。这项研究是在非平衡系统领域快速发展的事实下进行的，并在过去的二十年里受到了极大的关注。事实上，在许多应用中，材料在制备过程中(例如，通过球磨)或在使用过程中(例如，通过辐射)，都会受到某种外力的驱使而偏离平衡。***