Recrystallization Textures-Two Types of Modelling

Wierzbanowski, K.,Tarasiuk, J.,Bacroix, B.,Sztwiertnia, K.,Gerber, P. 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.1

Dislocation density is assumed to be the stored energy in a deformed material, i.e., the driving force in recrystallization. It can be estimated in diffraction experiments and it can also be predicted. Model calculations for b.c.c. structure give higher dislocation density for the orientations of the γ fibre compared with those of the α one. This explains the observed increase of γ fibre intensity (and decrease of α intensity) in the recrystallization texture of low-carbon steels, because nuclei appear preferentially in high stored energy regions. Hence, the oriented nucleation behaviour explains the texture change in this case. In other materials the oriented growth behaviour dominates. Phenomenological laws state that only these nuclei grow intensively which have a given misorientation with the deformed matrix. This description is frequently verified in f.c.c. metals and generally reported misorientations are 30°-50° rotations around the <111> axis. The above approach leads to good predictions of recrystallization textures in copper, brass and aluminium. The predicted results are still improved assuming that only these nuclei which are able to consume many deformed grains simultaneously (with different crystal orientations) grow effectively. Consequently, so-called compromise criterion and compromise functions are defined.

Microstructure, Texture and Mechanical Properties of Titanium Grade 2 Processed by ECAP (Route C)

M. Wroński,K. Wierzbanowski,D. Wojtas,E. Szyfner,R. Z. Valiev,J. Kawałko,K. Berent,K. Sztwiertnia 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.4

In the present work the properties of titanium grade 2 after ECAP processing with original route and regimes (route C, channelangle = 120°, deformation temperature 300 °C, number of passes up to 8) were examined. Texture development andmicrostructure parameters after ECAP processing and after recrystallization were determined using electron back scatterdiff raction and analysed. A signifi cant increase of the mechanical strength accompanied by some increase of ductility wasobserved in the deformed samples. The kernel average misorientation and average grain orientation spread were stronglyincreased after deformation, which confi rms the material refi nement and fragmentation. The proportion of low angle boundariesincreased after four ECAP passes, but after four consecutive passes high angle grain boundaries became predominant. Nodeformation twins were observed after four and eight ECAP passes. The material recrystallized after deformation retaineda fi ne grain microstructure. The textures of deformed and recrystallized samples were determined. It was found that textureafter 8 passes is more homogeneous that that after 4 passes, which partly explains higher ductility of this fi rst sample.

Effect of Reduction of Area on Microstructure and Mechanical Properties of Twinning-Induced Plasticity Steel During Wire Drawing

황중기,K. Wierzbanowski,유장영,A. Zargaran,김낙준 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.5

The effect of reduction of area (RA), 10%, 20%, and 30%, during wire drawing on the inhomogeneities in microstructure and mechanical properties along the radial direction of Fe-Mn-Al-C twinning-induced plasticity steel has been investigated. After wire drawing, the deformation texture developed into the major <111> and minor <100> duplex fiber texture. However, the <111> texture became more pronounced in both center and surface areas as the RA per pass increased. It also shows that a larger RA per pass resulted in a higher yield strength and smaller elongation than a smaller RA per pass at all strain levels. Although inhomogeneities in microstructure and mechanical properties along the radial direction decreased with increasing RA per pass, there existed an optimum RA per pass for maximum drawing limit. Insufficient penetration of strain from surface to center at small RA per pass (e.g., 10%) and high friction and unsound metal flow at large RA per pass (e.g., 30%) all resulted in heterogeneous microstructure and mechanical properties along the radial direction of drawn wire. On the other hand, 20% RA per pass improved the drawing limit by about 30% as compared to the 10% and 30% RAs per pass.

Effect of Rolling Asymmetry on Selected Properties of Grade 2 Titanium Sheet

M. Wroński,K. Wierzbanowski,M. Wróbel,S. Wroński,S. Wroński 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.5

Asymmetric rolling can be used in order to modify material properties and to reduce forces and torques applied during deformation. This geometry of deformation is relatively easy to implement on existing industrial rolling mills and it can provide large volumes of a material. The study of microstructure, crystallographic texture and residual stress in asymmetrically rolled titanium (grade 2) is presented in this work. The above characteristics were examined using the EBSD technique and X-ray diffraction. The rolling asymmetry was realized using two identical rolls, driven by independent motors, rotating with different angular velocities. It was found that asymmetric rolling leads to microstructure modification and refinement. At low deformations one observes a process of grain size decrease caused by the asymmetry of rolling process. In contrast, at the medium range of deformations the microstructure refinement consists mainly in subgrain formation and grain fragmentation. Another observation is that for low to intermediate rolling reductions (≤40%) the predominant mechanisms are slip and twinning, while for higher deformation (>40%) the main mechanism is slip. It was found that grain refinement effect, caused by the rolling asymmetry, persists also after recrystallization annealing. And finally, texture homogenization and reduction of residual stress were confirmed for asymmetrically rolled samples.

Microstructure Characteristics of ECAP Processed 1050 Aluminum After Deformation and 5 Years Later

M. Wroński,K. Wierzbanowski,R. Malik,S. Wroński,D. Wojtas,A. Baczmański,J. Tarasiuk 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.8

Modifcation of microstructure parameters of severely deformed 1050 aluminum after 5 years of recovery at ambient temperature was studied. The samples of 1050 aluminum were extruded using ECAP technique. The EBSD maps were recordedfor the initial material and for the deformed samples. Next, the latter samples were left at ambient temperature during 5 yearsand a full EBSD study of the material was repeated. It was found that all microstructure parameters and textures have changedafter this period. This is due to recovery and partial recrystallization, which took place in the samples during 5 years. Thepresented modifcations of material microstructure are important, e.g., in the aspect of long time service of mechanical partsproduced by severe plastic deformation techniques

Neutron Diffraction Study of Phase Stresses in Al/SiCp Composite During Tensile Test

Elżbieta Gadalińska,Andrzej Baczmański,Sebastian Wroński,Przemysław Kot,Marcin Wroński,Mirosław Wróbel,Christian Scheffzük,Gizo Bokuchava,Krzysztof Wierzbanowski 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.3

The stress partitioning between phases, phase stress relaxation as well as origins of Al/SiCp composite strengthening arestudied in the present work. In this aim, the measurements of lattice strains by neutron diffraction were performed in situ duringtensile test up to sample fracture. The experimental results were compared with results of elastic–plastic self-consistentmodel. It was found that thermal origin phase stresses relax at the beginning of plastic deformation of Al/SiCp composite. The evolution of lattice strains in both phases can be correctly simulated by the elastic–plastic self-consistent model onlyif the relaxation of initial stresses is taken into account. A major role in the strengthening of the studied composite plays atransfer of stresses to the SiCpreinforcement, however the hardness of Al metal matrix is also important.