Holder Aaron M, Siol Sebastian, Ndione Paul F, Peng Haowei, Deml Ann M, Matthews Bethany E, Schelhas Laura T, Toney Michael F, Gordon Roy G, Tumas William, Perkins John D, Ginley David S, Gorman Brian P, Tate Janet, Zakutayev Andriy, Lany Stephan
National Renewable Energy Laboratory, Golden, CO 80401, USA.
Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309, USA.
Sci Adv. 2017 Jun 7;3(6):e1700270. doi: 10.1126/sciadv.1700270. eCollection 2017 Jun.
Structure and composition control the behavior of materials. Isostructural alloying is historically an extremely successful approach for tuning materials properties, but it is often limited by binodal and spinodal decomposition, which correspond to the thermodynamic solubility limit and the stability against composition fluctuations, respectively. We show that heterostructural alloys can exhibit a markedly increased range of metastable alloy compositions between the binodal and spinodal lines, thereby opening up a vast phase space for novel homogeneous single-phase alloys. We distinguish two types of heterostructural alloys, that is, those between commensurate and incommensurate phases. Because of the structural transition around the critical composition, the properties change in a highly nonlinear or even discontinuous fashion, providing a mechanism for materials design that does not exist in conventional isostructural alloys. The novel phase diagram behavior follows from standard alloy models using mixing enthalpies from first-principles calculations. Thin-film deposition demonstrates the viability of the synthesis of these metastable single-phase domains and validates the computationally predicted phase separation mechanism above the upper temperature bound of the nonequilibrium single-phase region.
结构和组成控制着材料的行为。同构合金化在历史上是一种极其成功的调整材料性能的方法，但它常常受到双节线和旋节线分解的限制，这分别对应于热力学溶解度极限和对成分波动的稳定性。我们表明，异质结构合金在双节线和旋节线之间可展现出显著增加的亚稳合金成分范围，从而为新型均匀单相合金开辟了广阔的相空间。我们区分出两种类型的异质结构合金，即相称相和不相称相之间的合金。由于在临界成分附近的结构转变，性能以高度非线性甚至不连续的方式变化，提供了一种传统同构合金中不存在的材料设计机制。新颖的相图行为源于使用第一性原理计算的混合焓的标准合金模型。薄膜沉积证明了这些亚稳单相畴合成的可行性，并验证了在非平衡单相区域的上限温度以上通过计算预测的相分离机制。
