Kinetics of Ordered Domain Formation in Binary Alloys of D0₁₉ Type Order

Abstract

The present authors have developed a Time-dependent Ginzburg-Landau (TDGL) model for microstructural evolution of D0 19 type ordering, taking into account the crystal symmetry of the ordered phase. The D0 19 structure based on hcp is divided into four equivalent sublattices. The site occupation probabilities are given as a function of three order parameters and a composition parameter. Multiple types of variants of the structures are represented by the order parameters. Mean-field free energies are defined in a form of Landau type expansion with the order parameters and the composition parameter. Interfacial energies due to local variations of degrees of order and composition are given in a gradient square approximation. Kinetic equations for time-evolution of the order parameters and the composition one are derived from the Ginzburg-Landau type potential consisting of the mean-field free energies and the interfacial energy terms. We distinguish characteristic off-phase boundaries observed in Transmission Electron Microscopy (TEM) images in such as Cu 3 Sn and Ti 3 Al, and performed three-dimensional numerical simulations based on the kinetic equations.

Субструктура интерметаллического соединения Cu-=SUB=-3-=/SUB=-Sn в тонкопленочном состоянии

“…Соединение Cu 3 Sn существует в очень узкой области гомогенности и имеет упорядоченную структуру, как и многие другие интерметаллиды. Тип сверхструктуры был определен как D0 19 [15,16] микроскопии [20][21][22][23], а также теоретические расчеты [24,25] показали сильную зависимость скольжения по той или иной системе от условий эксперимента, таких как температура, скорость деформации.…”