Dynamic Model for the Nanocrystalline Implementation of the γ–α Martensitic Transition with an Increased Volumetric Effect

Abstract

For the γ–α martensitic transition (MT) in iron based alloys, the possibility of wave control over the growth of martensite crystals is analyzed for the cases of a great relative increase in volume. The main deformations corresponding to the Pitch distortion tensor are used as a basis for comparison with the typical Bain deformation. Particular attention is paid to the analysis of rod-shaped martensite crystals, whose growth is controlled by three longitudinal waves propagating along the orthogonal fourth-order symmetry axes. It is shown that consistency with the values of main deformations is attained when the wave dispersion law is taken into account. The possibility for the description of similar deformations in the patterns of three-dimensional deformation including the fine structure of transition twins and the limit variant of the formation of a degenerate dislocation structure is pointed out. However, the data on the interphase orientation Pitch relations are in good agreement just with the three-wave scheme of the formation of a rod-like crystals. Moreover, the group velocity at least of one of the waves belongs to the short-wave range to result in the wave controlling front size of ≈1.6 nm in the compression deformation direction. The correction for a rod-like morphotype of martensite nanocrystals seems to be promising when interpreting the formation mechanism for the peripheral zone of lenticular crystals.