Conception of New Phase Dislocation-Based Nucleation at Reconstructive Martensitic Transformations

Abstract

Abstract. The role of dislocations and the dynamical mechanism controlling the structural reconstruction in the process of nucleation and wave growth of new phase unit crystals at martensitic transformations in metallic systems are discussed. It has been established that near some rectilinear dislocations with lines and Burgers's vectors typical for the original phase, there are areas where an elastically deformed state is characterized by package of particularities unambiguously corresponding to the well defuute morphological attribute set (habit, orientation relationship, macroshear) of the martensite crystal. The distinctiveness of these areas for martensite nucleation is caused by character of strains reducing the magnitude of interphase energetic barrier. The elastic model of the dislocation-based nucleation center of martensitic crystal, allowing to select the dislocations being the most probable for nucleation and to make a martensitic crystal with the morphological attribute specific collection corresponding to each a dislocation, has been proposed. Such dislocations for certain Fe-, Cu-and TiNi-based alloys are indicated. New results for titanium nickel are presented in more detail.

Dynamic Model of the B2 → B19′ Martensitic Transformations Taking into Account an Intermediate Mesoscopic State

“…These lines change when they inherit dislocations during the B2 → B19′ transition. Thus, the use of orientations Λ║<1 2 0> B2 is not obligatory though possible [3][4][5][6]. This result indirectly confirms the correctness of OR (1) and (2), which makes expedient precision measurements of the OR to establish reliably their difference from the Bain relationships.…”

“…In particular, the possibilities for initiation of the direct B2-B19(19′) transformation with the formation of the habit planes close to { 78 39 48 } B2 observed in [2] within the limits of the concepts of heterogeneous nucleation and wave growth were studied in [3][4][5][6]. Based on the data about the orientational relationships between the lattice of Ti 3 Ni 4 particles (precipitated in the process of aging) and the lattice of the B2 phase, the dislocation with line orientation <1 2 0> B2 associated with the elastic field of particles and untypical for the homogeneous B2 phase was chosen.…”

Long-period states of a crystal finite-size-particle system

“…the course of propagation of the master wave process [65][66][67][68][69]. The model proposed in this work is one-dimensional, so it can provide only qualitative description of certain peculiarities of martensitic transformations.…”

Dynamic Model of the Formation of an Intermediate Mesorcopic State During B2 → B19 Martensitic Transformation

“…In our opinion, the exact fulfillment of the Bain OR would demonstrate that the conditions for material rotation of the lattice were not met in experiments with foils under examined conditions. In the general case, OR (11) and (12) are preferable.…”

“…It is well known (for example, see [11,12]) that the necessary conditions for the formation of the corresponding IES exist in elastic fields of edge dislocations with 1 1 0…”