Grain Boundary Ensemble Research Articles

Effect of Crystal Lattice Microstrain on the Parameters of Grain-Boundary Ensembles in Alloys with L12 Superstructure

Effect of Crystal Lattice Microstrain on the Parameters of Grain-Boundary Ensembles in Alloys with L12 Superstructure

Эволюция структуры и зернограничного ансамбля никеля при диффузионном отжиге в условиях сегрегирующей примеси (серебра) по границам зерен

Investigations of the effect of an impurity (silver) segregating along the grain boundaries of nickel on the evolution of the structure and grain-boundary ensemble under conditions of diffusion annealing at a temperature of 823 K for 6 hours have been carried out. It is shown that, under these conditions, the development of a diffusion-induced recrystallization (DIR) process is observed in the Ni(Ag) system, in contrast to the Ni(Cu) system, in which the process of diffusion-induced grain boundary migration (DIGM) was observed. The estimates made have shown that a possible reason for the fact that diffusion-induced migration of grain boundaries practically does not occur in the Ni(Ag) system can be significantly lower than in the Ni(Cu) system the value of osmotic pressure as the driving force for the DIGM process.

Investigating the grain structure of Cu-Al and Cu-Mn alloys via electron backscatter diffraction and optical metallography

Parameters of grain-boundary ensembles of Cu-Al and Cu-Mn solid solutions are analyzed quantitatively by optical metallography and scanning electron microscopy with the use of backscattering electron diffraction. It is established by both methods that the fraction of all special boundaries in a grain boundary ensemble and the fraction of twin boundaries Σ3 in the spectrum of special boundaries increase as the tacking fault energy in substitutional solid solutions diminishes.

Evolution of misorientation spectrum of grain boundaries of submicrocrystalline molybdenum upon deformation under conditions of grain-boundary diffusion of nickel

Comparative investigations of the concurrent evolution of the structure and the misorientation spectrum of grain boundaries of submicrocrystalline molybdenum have been performed upon free annealing and under the creep conditions at a temperature of 1023 K. It has been established that changes in the misorientation spectrum of grain boundaries of submicrocrystalline molybdenum upon annealing and creep are observed concurrently with boundary migration. The grain-boundary diffusion of nickel upon annealing leads to an increase in the fraction of grain boundaries of the special type with Σ17a in the grain-boundary ensemble of submicrocrystalline molybdenum. Under the creep conditions grain-boundary diffusion fluxes of nickel atoms favor transformation of low-angle boundaries into high-angle boundaries and growth in the angle of misorientation of the high-angle boundaries of submicrocrystalline molybdenum to 45°–60°.

Evolution of grain-boundary ensembles in nickel during boundary migration induced by copper diffusion

The effect of copper diffusion-induced grain-boundary migration on the structure and grain-boundary ensemble in nickel is studied to show that during migration, individual regions of random grain boundaries acquire misorientations corresponding to special boundaries of the Σ3 type. This leads to the formation in nickel of a grain-boundary ensemble with a content of special grain boundaries exceeding 70%.

Grain-boundary ensembles in ferritic-martensitic chrome steel

Grain-boundary ensembles in ferritic-martensitic chrome steel

Change in grain-boundary ensemble upon the A1 → L12 phase transition in Ni3Mn alloy

The grain structure of Ni3Mn alloy is investigated in the states with short-range and long-range atomic orders that arise at the A1 → L12 phase transition. It is found that in ordering annealing, new boundaries of a general type form, the fraction of special-type boundaries (including twin boundaries) is reduced, the share of high-energy special boundaries with Σ > 11 increases, and the alloy’s texture is transformed into a “gray” texture.

Evolution of a grain-boundary ensemble of submicrocrystalline molybdenum annealed under nickel diffusion along grain boundaries

The effect of annealing, including that performed under impurity diffusion from an external medium (coating), on an evolution of the structure and grain-boundary ensemble of submicrocrystalline molybdenum produced by severe plastic deformation is investigated. The distribution of grain boundaries over misorientations is shown to depend on the degree of strain experienced by the material during severe plastic deformation. Grainboundary diffusion fluxes of nickel atoms from the surface of the specimen are found to increase the fraction of special grain boundaries in the grain-boundary ensemble of submicrocrystalline molybdenum. Presumably, this is related to nucleation of new grains induced by the grain-boundary diffusion fluxes of nickel.