First-principles study of the nucleation and stability of ordered precipitates in ternary Al–Sc–Li alloys
First-principles study of the nucleation and stability of ordered precipitates in ternary Al–Sc–Li alloys
复制标题
DOI：
10.1016/j.actamat.2011.01.041
复制
发表时间：
2011-05
期刊：
影响因子：
9.4
通讯作者：
Z. Mao;Wei Chen;D. Seidman;C. Wolverton
中科院分区：
文献类型：
--
作者：
Z. Mao;Wei Chen;D. Seidman;C. Wolverton
采用第一性原理密度泛函方法研究了Al-Sc-Li合金中L12有序析出相的形核和稳定性。对于稀Al合金，存在三种可能的有序L12相：Al 3Sc，Al 3Li和Al 3Sc/Al 3Li核壳结构。为了计算成核行为，需要关于体热力学（静态总能量和振动自由能）、界面能量学和相干应变的信息。研究发现：（1）Al/Al_3Sc、Al/Al_3Li和Al_3Sc/Al_3Li共格界面的共格应变能较小，这是由于这些体系中原子尺寸失配较小;（2）计算了Sc和Li的亚晶格位置偏好，证明了Sc和Li在Al_3Sc（L_（12））和Al_3Li（L_（12））中共享相同的亚晶格位置，（3）Sc和Li在α-Al合金中的固溶度计算值与实验值符合较好，Sc的固溶度计算值与第一性原理结果符合较好;（4）计算了Al/Al_3Sc、Al/Al_3Li和Al_3Sc/Al_3Li（100）、（110）和（111）界面的界面能：Al/Al_3Sc界面能明显大于Al/Al_3Li和Al_3Sc/Al_3Li界面能;（5）结合体能和界面能得到Al 3Sc和Al 3Li沉淀物的成核势垒和临界半径;（6）将Al 3Sc/Al 3Li核/壳结构的能量稳定性与单独的Al 3Sc和Al 3Li核进行比较，并定量地确定核/壳结构在能量上有利的沉淀物尺寸范围。
First-principles density functional calculations are used to study the nucleation and stability of L12-ordered precipitates in Al–Sc–Li alloys. For dilute Al alloys, there are three possible ordered L12precipitates: Al3Sc, Al3Li and an Al3Sc/Al3Li core/shell structure. To calculate the nucleation behavior, information about bulk thermodynamics (both static total energies and vibrational free energies), interfacial energetics and coherency strain is required. The study finds the following: (1) the coherency strain energies for forming coherent interfaces between Al/Al3Sc, Al/Al3Li and Al3Sc/Al3Li are relatively small, owing to the small atomic size mismatches in these systems; (2) the sublattice site preferences of Sc and Li are calculated, and it is demonstrated that Sc and Li share the same sublattice sites in both Al3Sc(L12) and Al3Li(L12), in agreement with recent experimental results; (3) the calculated solubilities of Sc and Li in α-Al alloys are in good agreement with experimental values and, for Sc, agree well with prior first-principles results; (4) the interfacial energies for Al/Al3Sc, Al/Al3Li and Al3Sc/Al3Li for (100), (110) and (111) interfaces are calculated: the values of the Al/Al3Sc interfacial energies are significantly larger than those of the Al/Al3Li and Al3Sc/Al3Li interfaces; (5) combining the bulk and interfacial energies yields the nucleation barriers and critical radii for Al3Sc and Al3Li precipitates; and (6) the energetic stability of the Al3Sc/Al3Li core/shell structure is compared with individual Al3Sc and Al3Li nuclei, and the range of precipitate sizes for which the core/shell structure is energetically favored is determined quantitatively.