M. L. Lobanov

INTERRELATION BETWEEN THE ORIENTATIONS OF DEFORMATION AND RECRYSTALLIZATION IN HOT ROLLING OF ANISOTROPIC ELECTRICAL STEEL

The method of orientation microscopy (EBSD) is used to study the interrelation between deformation and recrystallization orientations in the structure of hot-rolled strip plate for the production of electrical anisotropic steel. It is shown that the interrelation between the orientations of recrystallized and deformed grains is implemented through a set of special off-orientations formed between the principal deformation orientations.

Special Misorientations and Textural Heredity in the Commercial Alloy Fe-3% Si

It is shown that, upon the rolling of a (110)[001] Fe-3% Si single crystal to different degrees of deformation, special misorientations of types Σ3, Σ9, Σ11, Σ19a, Σ27a, Σ29b, and Σ33a can be formed between the elements of the mesostructure (deformation twins, deformation bands, and shear bands). In the process of deformation, these misorientations are retained; the Σ3 misorientation is partially transformed into close misorientations of the Σ17b and Σ43c types. The nuclei of primary recrystallization with orientations close to (110)[001] are formed at twins, in transition bands, and in shear bands retain regions of special boundaries with the deformed matrix, which correspond to special misorientations arising during deformation. The experimental data obtained make it possible to draw a direct analogy between the processes of phase and structural transformations. In the case of phase transformations, a characteristic feature is the presence of orientational relationships between the crystal lattices of the initial and arising phases, which manifests in the parallelism of the close-packed planes and directions. In the case of structural transformations, the role of orientation relationships is played by special misorientations.

Interrelation of Crystallographic Orientations of Grains in Aluminum Alloy AMg6 Under Hot Deformation and Recrystallization

The structure and texture of a pipe from steel AMg6 produced by the method of hot pressing (extrusion) are studied. The important role of special (special and “half-special”) boundaries in the process of dynamic recrystallization is described.

Improving the production of superthin anisotropic electrical steel

Electrical steel with scattered ribbed texture may be used as the initial material in the production of superthin anisotropic electrical steel with perfect (110)[001] texture by the Littmann method. The possibility of producing superthin anisotropic electrical steel with 0.5 wt % Cu is demonstrated.

Effect of copper content, initial structure, and scheme of treatment on magnetic properties of ultra-thin grain oriented electrical steel

The effect of the copper content, initial structure, and scheme of treatment on the magnetic properties of an ultra-thin grain oriented electrical steel has been investigated. In the material with copper and an initial sharp texture, the nucleation of new grains upon primary recrystallization is connected with deformation twins; in the samples without copper and with copper and diffuse texture, it is connected predominantly with shear bands and transition bands. Upon heating at a rate of ∼0.004 K/s, the temperature of primary recrystallization in the copper-bearing samples is considerably higher than in the copper-free material. Upon heating at a rate of ∼4 K/s the appearance of new grains occurs almost simultaneously for all of the studied samples. In the samples with copper and initial sharp texture after annealing at 1050°C, a significant part of the volume is occupied by grains that had undergone normal grain growth; in the samples without copper and with copper and diffuse texture, anomalous growth is hardly observed at all. To obtain high final magnetic properties of the ultra-thin grain oriented electrical steel produced by the Littmann method, it has been suggested to use an grain oriented electrical steel with 0.5% Cu that exhibits the diffuse orientation of grains as the workpiece.

Formation of Special Misorientations Related to Transition Bands in Structure of Deformed and Annealed Single Crystal (110)(001) of Fe-3% Si Alloy

A transition band between two deformation bands retains for the most part the orientation (110)[001] and shrinks to a thin interlayer or boundary with increasing degree of deformation. At a certain stage of deformation, the microvolumes that are arranged along the interface of the bands become adjusted to special misorientations. During primary recrystallization, cube-on-edge (Goss) grains, which grow from the transition band, have portions of special boundaries common with the deformed matrix; these boundaries were found earlier between the deformation bands. This indicates that the local domains with special misorientations formed at the stage of cold deformation transform during annealing into the corresponding primary-recrystallization nuclei.

Investigation of Special Misorientations in Lath Martensite of Low-Carbon Steel Using the Method of Orientation Microscopy

Special misorientations between the laths of martensite packets in a low-carbon structural steel have been investigated by the method of EBSD-based orientation microscopy. It has been established that, in the process of the γ → α transformation, as a consequence of Kurdjumov—Sachs orientation relationships (ORs), special misorientations of the Σ3, Σ11, Σ33c, and Σ99a types are formed between the laths of a packet. The Σ3 misorientation is exact, and the remaining misorientations close to the special ones are formed with identical angular deviations as a result of the need to match the misorientations of laths in triple junctions (Σ3 + Σ11 → Σ33c, Σ3 + + Σ33c → Σ99a). Triple junctions of laths also appear in the packet that include a low-angle boundary (LAB) (between two laths of one orientation) and two boundaries of the Σ33c type, which can lead to the appearance of a boundary of the Σ41c type (Σ33c + LAB → Σ41c). The misorientation that corresponds to the Σ25b boundary discovered in the structure probably appears between the laths as a consequence of the fulfillment of the Nishiyama ORs.

Structure and texture formation over the width of ferritic-steel strip in hot rolling

In the hot rolling of ferritic steel, deformational texture (110)[001] is formed at the surface of the basic strip volume. It is dispersed when equiaxial recrystallizational grain structure appears. With transverse flow (near the edges) in hot rolling, the stable orientation {112}〈110〉 is formed in the surface layers. The cooling rate at the edges of the strip differs significantly from that at the center. That practically eliminates recrystallization processes and ensures maintenance of the extruded deformed (polygonized) grain structure, with the deformational texture in pure form.

ТЕКСТУРНАЯ НАСЛЕДСТВЕННОСТЬ ПРИ ФАЗОВЫХ ПРЕВРАЩЕНИЯХ В МАЛОУГЛЕРОДИСТОЙ НИЗКОЛЕГИРОВАННОЙ ТРУБНОЙ СТАЛИ ПОСЛЕ КОНТРОЛИРУЕМОЙ ТЕРМОМЕХАНИЧЕСКОЙ ОБРАБОТКИ

The orientation microscopy (EBSD) was used for studying of the structural and textural states of the low-carbon low-alloy pipe steel close to 06G2MB after the thermomechanical controlled processing (TMCP) and subsequent thermal treatments – heating up to 1000  °C followed by: 1) water quenching; 2) isothermal quenching with holding at 300  °C; 3) slow cooling in a furnace. All heat treatments included double phase recrystallization: α  →  γ  →  αN (where αN is martensite, ferrite or bainite, respectively). The texture obtained after TMCP, was formed mainly by two strong orientations {112} and two weaker orientations close to {110} . It was shown that despite dual phase recrystallization the main crystallographic orientations of bainite after TMCP and after isothermal quenching are consistent with each other. This indicates some mechanism of structure and texture heredity within the material. The structures obtained through other thermal treatments, martensite and ferrite, were also characterized by complex multi-textures. Part of the basic textural components of martensite and ferrite were the same as in case of bainite. All structures after various thermal treatments have common spectrum of high angle boundaries with the most pronounced boundaries of the coincidence site lattice (CSL): Σ3, Σ11, Σ25b, Σ33с, Σ41c. It has been demonstrated that the orientations inside textures of all obtained structures are associated with the major orientations of the strained austenite grains formed as a result of hot rolling during TMCP and the orientation relationships (ORs) that are intermediate between ORs of Kurdyumov-Sachs and Nishiyama-Wasserman. In all cases, the fact of correspondence between orientation bonds of textures in initial and all resulting states is explained through a selective initiation of phase transformations (both shear and diffusion) on crystallographic (including special) boundaries close to the CSL boundaries Σ3 and Σ11.

EFFECT OF CARBON ON TEXTURE FORMATION IN ELECTRICAL STEEL Fe - 3% Si UNDER HOT ROLLING

The structure and texture of strip plate from anisotropic electrical steel after hot rolling are studied as a function of the content of carbon in the metal. The study is performed with the help of orientation microscopy based on diffraction of back-scattered electrons (EBSD).