Phase transformations and structure of Ni–Mn–In alloys with varying ratio Ni/Mn

The fine structure of Ni–Mn–In alloys has been studied when manganese atoms are substituted for nickel atoms in an annealing state. The concentration dependence of the critical temperatures and the structures of the alloys have been discussed. It has been found that, as manganese atoms replace nickel atoms, the structure after annealing is changed from a two-phase (L2₁ + martensite) to single-phase L2₁ structure. The martensitic transformation in Ni₄₇Mn₄₂In₁₁ alloy is accompanied by the formation of modulated 14M martensite.     

Features of bicrystal growth during the directional crystallization of metal melts

The factors responsible for the formation of different configurations of boundaries between adjacent crystallites during their growth from melt by Bridgman and Czochralski methods have been considered by an of example Fe–20 wt % Ga alloy and Ni bicrystals. It is found that the configuration of intercrystallite boundary is related to the features of crystallite growth, caused by the strained state of intercrystallite and interphase (crystal–melt) boundaries, the difference in the linear thermal expansion coefficients of the crystallite boundaries and bulk, and the shape (geometry) of the bicrystal cross section. It is suggested that the strained state of boundaries and the formation of substructure in crystallites during directional crystallization from metal melt are significantly affected by their deformation under the melt weight.

     

Determining orientation relationships for the <Emphasis Type="Italic">B</Emphasis>2 → <Emphasis Type="Italic">B</Emphasis>19′ transformation in single crystal titanium nickelide according to the texture of <Emphasis Type="Italic">B</Emphasis>19′ martensite

A precision method for determining orientation relationships upon the B2 → B19′ transformation in titanium nickelide has been developed. The method is based on analyzing the martensite texture formed in the initial high-temperature B2 phase of a single crystal having a high degree of perfection. The orientation relationships between the B19′ lattice and the initial B2 lattice of the TiNi single crystal were established from the B19′ martensite texture formed in single crystals of titanium nickelide upon the B2 → B19′ transformation and from measurements of the lattice parameters. Crystal mechanism of B19′ martensite was proposed which included the shear in the (21-1) B2 plane in the direction [−11-1] B2 by 10°. Such a shear system is typical of the bcc crystals at deformation by twinning. Absolute shear values are in a ratio of 1:4 for B2 → B19′ transformation and for twinning, respectively. Martensite deformation at an invariant lattice is accompanied by small rotations of martensite crystals (±1.6°), that increases the quantity of martensite orientations from 12 to 24.     

Orientation relationship and the mechanism of martensite transformation in medium-carbon steel with batch martensite

Exact orientation relationship for martensite transformation in medium-carbon 37KhN3A steel with lath martensite are determined. The mechanism of deformation during the transformation of martensite in steel is described.     

On similarity homogeneous locally compact spaces with intrinsic metric

In this article, we generalize partially the theorem of V. N. Berestovskii on characterization of similarity homogeneous (nonhomogeneous) Riemannian manifolds, i.e., Riemannian manifolds admitting transitive group of metric similarities other than motions to the case of locally compact similarity homogeneous (nonhomogeneous) spaces with intrinsic metric satisfying the additional assumption that the canonically conformally equivalent homogeneous space is δ-homogeneous or a space of curvature bounded below in the sense of A. D. Aleksandrov. Under the same assumptions, we prove the conjecture of V. N. Berestovskii on topological structure of such spaces.     

Carbon distribution in the martensite structure of structural steel

The martensite structure of a hardened pseudosingle crystal of grade 37KhN3A medium-carbon structural steel (0.37 wt % C, 1.50 Cr, 3.0 Ni, 0.33 Mn) had the form of coarse packets with dimensions of to 1 cm in the cross section. Every packet was composed of six-orientation martensite crystals arising on one common austenite plane of type {111}. The position of three texture maximums was determined using an X-ray diffractometer for every orientation. In addition, the position of four maximums of retained austenite was found. The periods of martensite lattices and retained austenite as well as the carbon concentration in martensite lattices and near the boundaries are determined.     

Crystallographic analysis of the <Emphasis Type="Italic">B</Emphasis>2 → <Emphasis Type="Italic">B</Emphasis>19′ martensite transformation in titanium nickelide

A phenomenological theory of martensite transformation is used to determine (select) the mechanism of B2 → B19′ transformation. The most realistic mechanism corresponds to the minimum additional rotation of a martensite plate needed to maintain the invariance of the habit plane. Equal values of the macroscopic shear direction and extent, the habit plane, the deformation for the invariant lattice, and the general deformation of shape are obtained for four different deformations. However, the supplementary rotation for each option is different. The minimum angle of rotation is observed for deformation by a martensite transformation with {21-1}B2 plane shear in the 〈-11-1〉 direction.     

Crystallographic analysis of martensitic transformation in an iron-nickel alloy with twinned martensite

A variant of the crystallographic theory of martensitic transformations is proposed, based on a mechanism of lattice deformation in which the angle of rotation of a martensite plate is reduced to a minimum. In an iron-nickel alloy with twinned martensite, the least angle of rotation corresponds to the deformation of the austenite lattice by shear on the (111) plane in the $\left[ {11\bar 2} \right]$ direction proposed by Kurdyumov and Sachs as the first shear in the two-shear theory of martensite formation in steel.     

Crystallographic specific features of the martensitic structure of Ni<Subscript>47</Subscript>Mn<Subscript>42</Subscript>In<Subscript>11</Subscript> alloy

The structure of Ni₄₇Mn₄₂In₁₁ alloy after annealing has been investigated. It is shown that the martensitic transformation in Ni₄₇Mn₄₂In₁₁ alloy upon cooling is accompanied by the formation of 14M modulated martensite. Crystallographic analysis of the martensite structure has been performed. The orientation relationships between the high-temperature austenitic phase and martensite and habit planes of the martensite plates have been determined.