# Review of Magnetic Properties and Texture Evolution in Non-Oriented Electrical Steels
## 4 Effects of Thermomechanical Processing  
Thermomechanical processing (TMP) plays an important role in the final microstructure and magnetic properties of electrical steels [35; 36; 37; 38; 39; 40]. TMP involves reheating, hot-rolling, cold-rolling, and an intermediate and final annealing (recrystallization annealing) process, which influence the inclusion distribution, microstructure, and texture, which in turn influence the final magnetic properties. The product's final magnetic properties (after final annealing) are directly affected by the texture distribution [41]. The texture of electrical steels is influenced by the following factors: (1) steels chemical composition; (2) possible \(\gamma\) to \(\alpha\)-phase transitions during cooling; (3) high solidification cooling rates; (4) directional solidification; (5) recrystallization annealing after the cold-rolling process; (6) deformation regime [42]; and (7) magnetic annealing [43]. Rolling temperature has a significant influence on texture and microstructure evolution [38]. The texture produced by hot-rolling also affects the texture and microstructure evolution during the cold-rolling process [44]. Nuclei orientation and the growth rate of these nuclei influence the recrystallization texture. There are two main theories that describe texture development, one of which is the nucleation-oriented theory. This theory assumes that nuclei that have a specific orientation grow rapidly. The fast growing nuclei orientation affects recrystallization texture [40]. The second theory is a growth-oriented theory, which assumes that there are some specific orientation relationships for which grain boundaries migrate more rapidly [17]. Euler angles are the three rotations that align the \(<\)100\(>\) direction with the rolling direction. The orientation distribution function (ODF) in Figure 6 shows the sections when one Euler angle (Bunge notation) \(\varphi_{2}\) is at (a) 0\({}^{\circ}\) and (b) 45\({}^{\circ}\). Figure 4: Si content with respect to critical cooling rates. The samples were annealed at 850 \({}^{\circ}\)C for 1 h, and then quenched at different cooling rates [20]. Figure 5: B2/D0\({}_{3}\) domain size regarding critical cooling rates [33]. The notation of texture [110]\(<\)001\(>\) represents the planes of the form [110] that are parallel to the surface of the sheet, and directions of the form \(<\)001\(>\) that are parallel to the rolling direction [45]. Rolling textures are often represented by \"fibers\" instead of specific orientations. During the thermomechanical processing of electrical steels, some specific textures are observed: \(<\)111\(>\) //normal direction [ND] (\(\gamma\)-fiber), \(<\)100\(>\)// [ND] (\(\theta\)-fiber), \(\{\)hhl\(\}\)\(<\frac{h}{T}+1\frac{h}{T}+2\frac{h}{T}>\) (\(\alpha^{*}\)-fiber), \(<\)110\(>\) // rolling direction [RD] (\(\alpha\)-fiber), and \(<\)100\(>\)// RD (\(\eta\)-fiber). The orientation and fiber structures are shown in Figure 6[46]. In electrical steels, \(\alpha\)-fiber, \(\alpha^{*}\)-fiber, and \(\gamma\)-fiber are commonly formed during thermomechanical processing [47]. This is caused by the oriented nucleation behavior at elongated deformation bands. The \(\gamma\)-fiber and \(\alpha\)-fiber deformation bands are formed by the rotation mechanisms in the hot- and cold-rolling processes [35, 47, 48]. For electrical steels used in rotating magnetic field (electric motors), \(\lambda\)-fiber is the ideal texture for good magnetic properties because it has the best magnetization direction \(<\)001\(>\) in the plane of the sheet. In this case, any [hkl] with \(<\)001\(>\) axes in the plane of the sheet is preferred. For magnetic circuits, the best texture is \(\eta\)-fiber, since this makes it possible to orient the magnetic flux along the \(<\)100\(>\) direction for almost its entire path. The \(\gamma\)-fiber is not favorable for magnetic properties of electrical steels [49]. In conventional steel processing, \(\gamma\)-fiber evolves preferentially after annealing [50].