Investigations and computer simulations of the intergrain diffusion in submicro-and nanocrystalline metals

Abstract

Investigations of the features of the diffusion along grain boundaries and of the diffusion-controlled processes in submicroscopic and nanocrystalline materials produced by methods of intense plastic deformation are reviewed. To determine the parameters of the diffusion along grain boundaries and triple junctions in metals, which are independent of the results of processing of diffusion experiments based on diffusion models, results of a molecular dynamic investigation of the diffusion in nanocrystalline copper considered as an example are presented. Comparison of the features of grain boundary diffusion in submicroscopic and nanocrystalline materials produced by various methods is performed.

Self-Diffusion Parameters of Grain Boundaries and Triple Junctions in Nanocrystalline Materials

“…Here we assume that the triple junction area is a homogeneous phase Grain Boundary Diffusion, Stresses and Segregation in the form of a cylinder of radius R [1]. Assuming that the shrinkage of grain boundary δA is equal to nRl TJ , using (1) and stereometrical identity we derive equation for calculating ζ GB and ζ TJ [4]:…”

Investigations of the thermal stability of the microstructure of titanium produced by intense plastic deformation

“…At the same time, some fundamental, usually structure-insensitive properties of these materials, such as the elastic modulus, Curie and Debye temperatures, specific heat, etc., are varied [3]. It has been revealed that for SMC and NS metals produced by plastic deformation the grain-boundary diffusion coefficients are several orders of magnitude greater compared to those for individual GBs in bicrystals or GBs in coarse-grained polycrystals [13][14][15][16][17][18][19]. The increased diffusion coefficient for the state under discussion makes the structure highly sensitivitve to the action of the environment.…”

“…Experimental investigations on this line are difficult in view of the small size of structure elements and of the atomic scale of the processes involved. The same circumstance necessitates the study of the mechanisms of diffusion-controlled processes in NC materials by methods of computer simulation at the atomic level [16]. Investigations at this level form a basis for developing models which would allow one to predict the behaviour of NC materials by using the methodology of multiscale simulation of materials and processes [9] in combination with methods of mesomechanics [32].…”

“…These approaches also allow one to test the models by using computer experimentation. The recent experimental and theoretical investigations of the structure and properties of nanomaterials and of the mechanisms of the physicochemical processes occuring in them strongly suggest that computer simulation is extremely urgent in carrying out basic research and, especially, in developing NC materials [9,16,32].…”