Reconstruction of Martensitic Nucleation Process from Morphological Attributes

Abstract

Within the framework of the concepts of heterogeneous nucleation and wave growth of martensite the refinement of a technique of account of wave normals NW to expected habits planes are carried out. The technique allows to connect orientations of NW with definite areas of nucleation of crystals in an elastic field of defects. The specific results are for system Cu-Zn. As separate rectilinear dislocations with lines [l 1 71 and dislocation loops basic elements of which are pieces of these lines are considered here as probable centers of nucleation. It is shown, that the spectrum of NW can be coordinated with experimentally observable space distribution 8f normals N, in a vicinity of a pole[2 11 121. The similar coordination opens additional opportunities to reconstruct a stage of martensle nucleation from morphological attributes and to transform a distribution of habits in the informative parameter.

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.…”

“…For the DNC associated with the initial directions Λ ║<1 11> B2 , the wave normals are close to <1 5 Analogously, for Λ║<1 10> B2 , the habit planes {223} B2 are observed with wave normals close to n 1 ║<1 10> B2 and n 2 ║<001> B2 . The Λ → Λ′′ transition is accompanied by deviations of the wave normals and the (22 3 ) B2 → (0.48 0.39 0.78 ) B2 change of the habit plane.…”

“…Directions (6) correspond to images Λ′ of the symmetry axes of the second and third orders after strain (5), that is, when the Bain-type OR…”

“…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.…”

On the Applicability of the Concept of Control Wave Process to the B 2→R Martensitic Transformation in B 2 Titanium Nickelide Alloys

“…From them the B2→B19 MT involves the maximum change of the relative volume, and the B2→R MT involves the minimum change of the relative volume. In [7,8] it was demonstrated that methodology suggested in [1-4] provides a reasonable description of the habit planes of the B2→B19 MT for which it is suffice to consider the threshold regime of propagation of the control wave process (CWP). Recall that the concept of the initial excited state (IES) arising in the elastic field of a dislocation nucleation center (DNC) plays the key role in the dynamic theory [1][2][3][4].…”