Formation of an Ordered Structure in the Cu–50 at % Pd Alloy

Electron microscopic study of the structure evolution of the equiatomic Cu–50Pd alloy in the course of transformation of the А1 disordered phase into the ordered B2 phase is carried out. The disordered state in the initial samples was formed by two ways, namely, by severe plastic deformation by rolling (е ≈ 3.8) and quenching from 700°С. The ordering was realized by annealing of initial samples at 350°С for 2 weeks. Literature data on the fact that the rate of atomic ordering with the formation of the В2 structure in the preliminarily deformed Cu–Pd alloy is substantially higher than that of the alloy quenched from a high temperature are confirmed. The annealing of the preliminary deformed Cu–50Pd alloy leads to the formation of recrystallized ordered structure with a grain size of less than 1 µm. It was found that, at 350°С, B2-phase particles in the form of rods precipitate and grow in the disordered matrix of the quenched alloy.