On tri-axial periodic modulated structure in metallic alloys

Abstract

The calculation of the diffuse scattering of X-rays (the intensity of the satellite reflections about the Bragg reflections from supersaturated solid solution) has been carried out for the description of the structure of some metallic alloys in the initial stages of the decomposition of the supersaturated solid solution with the help of the model of a tri-axial modulated periodic structure (1,2) (the modulation of the interplanar spacing and the scattering power in three 〈100〉 directions simultaneously). The comparison of the results of quantitative measurements of the satellite intensity in various directions away from the Bragg maxima (in the directions 〈100〉 and 〈110〉) for the initial stage of aging of the Fe-Be alloys with 16.5 and 19.5 at.% Be after annealing at 400° with the results of calculation has proved the correctness of the proposed model. The study of the satellite intensity in various directions depending on different parameters of the model (on the period of modulation L and the degree of modulation Δa a ) permits an explanation based on the proposed model, the observations in the previously studied alloys with the modulated periodic structure (in such alloys as “CuNiFe,” “CuNiCo,” “ticonal” others), in contrast to the Fe-Be alloys, of satellites only in the directions 〈100〉.