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- 저자 : K. Sztwiertnia (검색결과 2 건)
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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.
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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.
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