Thermodynamic stabilization of nanocrystallinity
Thermodynamic stabilization of nanocrystallinity
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DOI：
10.3139/146.101152
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发表时间：
2005-10-01
期刊：
影响因子：
--
通讯作者：
Birringer, R
中科院分区：
文献类型：
--
作者：
Krill, CE;Ehrhardt, H;Birringer, R
纳米晶体材料是由纳米尺寸的晶粒组成的多晶体，这些晶粒被界面网络（晶粒或相边界）分隔开，这些界面通常对系统的总能量有积极的贡献。因此，存在一个热力学驱动力，减少整体界面面积，这使得这样的系统本质上不稳定的粗化。后一个过程需要界面迁移和伴随的任何性能增强的超细晶粒尺寸的影响恶化。我们描述了一种策略，显着减少甚至消除驱动力的晶粒生长的纳米晶材料通过故意偏析的溶质原子到边界的核心区域。适用于含高达20 at.%的Pd-Zr固溶体Zr，该策略产生纳米晶试样，表现出相对于晶粒生长的异常高的热稳定性，延伸到熔点附近。在偏析稳定系统中晶界的迁移和有序合金中反相畴界之间绘制了平行线。
Nanocrystalline materials are polycrystals made up of nanometer-sized grains separated by a network of interfaces - grain or phase boundaries - that generally make a positive contribution to the total energy of the system. Consequently, there exists a thermodynamic driving force for reducing the overall interface area, which renders such systems intrinsically unstable against coarsening. The latter process entails interface migration and the concomitant deterioration of any property enhancements effected by the ultrafine grain size. We describe a strategy for significantly reducing or even eliminating the driving force for grain growth in nanocrystalline materials via the deliberate segregation of solute atoms into the core region of boundaries. Applied to Pd-Zr solid solutions containing up to 20 at.% Zr, the strategy yields nanocrystalline specimens manifesting an unusually high thermal stability with respect to grain growth, extending to the vicinity of the melting point. Parallels are drawn between the migration of grain boundaries in segregation-stabilized systems and antiphase domain boundaries in ordered alloys.