The distribution of dislocation density was investigated experimentally in Al single crystals with various concentrations of Cu impurity (0.0002, 0.005 and 0.05wt%) that were obtained upon the crystallization of the melt under the action of a pressure and the gravitational-field component directed along the surface of the crystallization front. It was found that a strong non-uniformity in the dislocation distribution arose in cross sections of the crystals in the direction of the field and this non-uniformity increased with increasing gravitational-field component and decreasing in the impurity concentration and rate of crystallization of the melt. It was found that the degree of non-uniformity of the dislocation distribution in the crystals substantially depended on the magnitude of pressure at which the crystallization of the melt was realized and reaches a maximum at a certain pressure that was optimum for given conditions of the process of phase transformation.

Formation of a Dislocation Structure of Aluminum Single Crystals under the Action of Pressure and Gravitational Field on the Melt. V.O.Esin, A.S.Krivonosova, I.Z.Sattybaev, T.G.Fedorova: The Physics of Metals and Metallography, 2007, 103[3], 317-23