Details of the Formation of Superstructures in the Process of Ordering in Cu-Pt Alloys

Abstract

Alloys of Cu-Pt [1] are of interest for research, since the phase transitions "order - disorder" at different concentrations of components form several types of superstructures. In the alloy Cu3Pt the ordering L12 superstructure formed on the basis of fcc lattice. In the ordering of the fcc lattice of the disordered solid solution the equiatomic composition transformed into the L11 superstructure with an rhombohedral crystal lattice (a state with an L11, whose angles α, β, and γ are other than π/2). A CuPt3 in an ordered state has an L13 superstructure (a state with an L13, whose angles α, β, and γ are other than π/2). A possible existence of an ordered phase containing 20 at.% Pt was reported in the literature [2], which corresponds to the composition of Cu4Pt (type of superstructure was not defined). In other sources, an occurrence of an ordered compound, Cu7Pt, was predicted, containing 12.5 at.% Pt [3]. Computer experiments performed on the Monte Carlo method, showed that the alloys of the Cu - Pt different composition components undergo phase transformations "disorder - order" from the FCC to the structures of different symmetry [4,11]. This paper presents the results of a study of the structural transformations in the alloys Cu3Pt, CuPt, CuPt3 (superstructure L12, L11, L13), containing shear antiphase boundaries (APB) in the planes {111}.

Simulation of Thermal Cooling Curves in the Process to Ordering Alloys by the Monte Carlo Method

“…A large number of works on the theory to ordering alloys and modeling to phase diagrams are presented in the literature, where the types and kinetics for order-disorder phase transitions are discussed, the structural and energy characteristics to defects are described, and the stoichiometry and temperatures to phase transitions are calculated [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In [7,8], a two-dimensional model was proposed that allows one to study the kinetics of ordering for alloys for the model to a rigid crystal lattice.…”

“…This model was generalized to the case to three-dimensional lattices and was used to study the structural-phase transformations of a number for stoichiometric alloys [9][10][11][12][13], including to take into account the effect to antiphase boundaries [10]. In our recent works, a similar model was used to study the kinetics of alloy ordering [14][15][16], determine the possible structural states to alloys based on two-dimensional and three-dimensional lattices [17][18][19][20], calculate the sublimation energy for a binary alloy, taking into account the effect for the alloy composition on interatomic interactions [18,20], mathematical modeling of double state diagrams to congruent type [20].…”