Hot Rolling of Magnesium Single Crystals

To analyze the effect of the initial orientation in the activity of twinning and texture development, magnesium single crystals were rolled at 400 °C (nominal furnace temperature) in two specific orientations. In both orientations, the rolling direction of the sheet (RD) was parallel to the c-axis. For orientation 1, the 112¯0 direction was parallel to the normal direction (ND), and for orientation 2, it was parallel to the 101¯0 direction. The samples were rolled at 30%, 50% and 80% of thickness reduction. After rolling, all the samples were quenched in water to retain the microstructure. The microstructure and texture evolution were characterized by X-ray diffraction and Electron Backscatter Diffraction (EBSD). The initial single crystals were turned into polycrystals, where most grains had their c-axis almost parallel to the ND, and this reorientation was explained by extension twinning. The active twin variants in orientation 1 aligned the basal plane ~30° from the sheet plane and caused a weaker basal texture compared to orientation 2, where the twin variants aligned the basal plane almost parallel to the sheet plane. Strain localization inside contraction twins was observed, and consequently, non-basal grains nucleated inside these twins and weakened the final basal texture only in orientation 1.

Investigation of the prediction capability of Yld89 yield criterion for highly anisotropic sheet materials

In the present work, the prediction capability of Yld89 criterion from anisotropic yield func- tions was investigated in the view of the anisotropic behavior of the sheet metals. Investigation was conducted on two highly anisotropic sheet materials: an aluminum alloy (AA2090-T3) and an advanced high strength steel (TRIP 780). The in-plane variation of material anisotropy and normalized yield surface contours were considered in the evaluation of the prediction capability of the criterion. Firstly, the model coefficients were determined according to stress and strain based definitions. Then, the planar variations of the yield stress and plastic strain ratios and normalized yield surface contours of the materials were predicted according to both identification procedures. Finally, the computed results were compared with experiments to evaluate prediction capability of the model. It was observed from the comparisons that the pla- nar variations of the yield stress ratio could successfully predicted by stress based definition, while the variations of the plastic strain ratios in the sheet plane could accurately predicted by strain based definition. Besides, it was determined that elastic region predicted from strain based definition was larger than stress based definition for AA2090-T3, while the predicted elastic region from stress based definition was slightly larger in than that of strain based defi- nition for TRIP 780 material.

Application of Associated and Non-Associated Flow Metal Plasticity for F.S.S Sheet

In the last decade, several phenomenological yield criteria for anisotropic material has been proposed to improve the modeling predictions about sheet metal-forming processes. In regard to this engineering application, two proprieties of models have been used. If the yield function and the plastic potential are not same (not equal), the normality rule is non associative flow rule (NAFR), otherwise, when the stresses yield has been completely coupled to the anisotropic strain rate ratio (plastic potential), is called the associated flow rule (AFR). The non-associated flow rule is largely adopted to predict a plastic behavior for metal forming, accurately about à strong mechanical anisotropy presents in sheet metal forming processes. However, various studies described the limits of the AFR concept in dealing with highly anisotropic materials. In this study, the quadratic Hill1948 yield criteria is considered to predict mechanical behavior under AFR and NAFR approach. Experiment and modeling predictions behaviour of normalized anisotropic coefficient r (θ) and σ (θ) evolved with θ in sheet plane. and the equibiaxial yield stress σb was assumed σb=1 but the rb-values was computed from Yld96 [15].

Shear Banding in Rotated Goss Grains and its Effect on the Formation of Cube Texture in Non-Oriented Electrical Steel

Cube texture ({001}<100>) is a desired final texture in non-oriented electrical steel sheets used as magnetic cores because it contains two easy <100> axes in the sheet plane, which is beneficial to the magnetic properties. However, the cube texture is very difficult to form in non-oriented electrical steels through conventional rolling and annealing. It has been shown that after conventional rolling, the deformed <111>//ND (normal direction) grains provided nucleation sites for the unfavourable <111>//ND texture during recrystallization, leading to a final <111>//ND texture. To eliminate the <111>//ND texture and promote the {001}<100> texture, an uncommon rolling process, i.e. inclined rolling, was adopted in this study. By rotating the hot rolling direction by 60° around the ND, an uncommon initial texture, the rotated Goss ({110}<110>), was intentionally generated. This was intended to change the orientation flow during plastic deformation, and suppress the formation of the conventional <111>//ND texture in the deformed microstructure. Plane-strain compression (rolling) of the rotated Goss grains produced shear bands within these grains due to their large Taylor factor. Electron backscatter diffraction (EBSD) characterization of the shear bands illustrated that, crystallites with the cube orientation were formed within these shear bands. During recrystallization, the shear bands provided preferential nucleation sites, and the cube crystallites preferentially nucleate within the shear bands. These cube crystals can then grow into the deformed matrix, and lead to the formation of a strong cube texture in the final annealed steel sheets.

Reasons for banding formation in steels of K60 strength category

Active development of pipeline transport of gas and oil with increasing working pressure to 120 atm. increases the need for pipes with large wall thickness that correspond the requirements of the DNV OS-F101 standard. Quality of continuously cast billets is decisive for improving quality of sheet metal for main pipelines. Inheritance of cast structure imperfections by a hot-rolled sheet leads to structural heterogeneity of the strip and the layered nature of the fracture surface and adversely affects the mechanical properties and corrosion resistance. Structural heterogeneity of rolled products is appeared in the form of axial ferrite-martensitic metal banding and metal banding in the main section of the sheet consisting of a mixture of ferritic and pearlitic grains — pearlitic metal banding. The flatness in the axial zone of the rolled products is due to axial chemical heterogeneity which is objectively formed during crystallization of the continuously cast billet and further phase transformations. The axial chemical inhomogeneity does not resolve despite the recrystallization of the structure and deformation and the high content of alloying elements contributes to the formation of the martensite phase and large carbonitride precipitates. The cause of pearlite bands is considered usually to be the presence of dendritic segregation. According to us the reason of this metal banding is the shift of the temperature front of γ → α transformation parallel to the sheet surface in depth as a result of which before the next volume of formed ferrite the concentration of carbon dissolved in austenite increases with the subsequent formation of pearlite. The enrichment of austenite proceeds along the boundaries preserved from the δ → γ transformation during cooling the slab and the formed pearlite structure repeats the shape of the boundaries of these grains in the section parallel to the sheet plane.

Achievements of Nearly Zero Earing Defects on SPCC Cylindrical Drawn Cup Using Multi Draw Radius Die

In recent years, the old-fashioned cylindrical cup shapes are still widely used, and there are many defects which could not be solved yet. In the present research, the classical earing defects, which are mainly caused by the material mechanical property of the anisotropic property of the material (R-value), are focused on. The multi draw radius (MDR) deep drawing die is applied and investigated to achieve nearly zero earing defects by encountering the R-value during the deep drawing process. Based on the experiments, in different directions in the sheet plane, the somewhat concurrent plastic deformation could be controlled, and the uniform elongated grain microstructure and uniform strain distributions on the cup wall could be achieved. Therefore, on the basis of these characteristics, the earing defects could be prevented, and the nearly zero earing defects could be achieved. However, to achieve the nearly zero earing defects, the suitable MDR die design relating to the R-value should be strictly considered. In the present research, to apply the MDR die for the medium carbon steel sheet grade SPCC cylindrical drawn cup, the following was recommended: the large draw radius positioned at 45° to the rolling direction and the small draw radius positioned along the plane and at 90° to the rolling direction. Therefore, in the present research, it was originally revealed that the nearly zero earing defects could be successfully performed on the process by using the MDR die application.

Peculiarities of quasi-adiabatic dynamics of charged particles in current sheets with magnetic shear

&lt;p&gt;The dynamics of quasi-adiabatic ions in the current sheet (CS) of the Earth's magnetotail during substorms is investigated, when CS is thinned, and the scale of the magnetic inhomogeneity is about proton gyroradius. Experimental data indicate sometimes that the shear magnetic component from the interplanetary magnetic field can penetrate within the magnetosphere and support self-consistent currents. The numerical model of CS is constructed, taking into account the normal magnetic component and shear component of three types: 1) constant profile within CS, 2) bell-shaped and 3) antisymmetric ones. Poincar&amp;#233; maps characterizing quasi-adiabatic dynamics of ions are studied. The jumps of quasi-adiabatic invariant of motion are calculated, and comparison is made with the case of the absent magnetic shear. It is shown that the presence of constant and bell-shaped magnetic components in the current sheet leads to the asymmetric scattering of particles in the North-South direction after their interaction with CS and corresponding differences in the structure of the phase space. It is demonstrated that the jumps of the approximate invariant Iz depend on the location of the plasma source in the Northern or Southern hemispheres.&amp;#160; At the same time, for configurations with anti-symmetric shear component, the particle scattering near the sheet plane is negligible, therefore in this case it is no scattering asymmetry, and the jumps of invariants of motion are smallest; they do not depend on the value of the magnetic field amplitude inside CS. Applications of these results to interpret experimental observations are discussed.&lt;/p&gt;

Compositional Principles of the Organization of the Sheet Plane

Considering the increasing role of science-based methodologies of graphic design practice in scientific research and development of educational guidebooks for future specialists, this article is focused on importance and consistency of correct usage of terminology of composition theory, namely categories, attributes, means. Recently, the need to provide an educational process with specialized educational literature arose because of the establishment of design programs in many academic institutions, in particular, graphic design departments. First of all, it concerns the theoretical bases of graphic design. As a result of aforementioned, we see the appearance of many editions on issues of the basics of composition and morphogenesis. However, the major part of them requires a serious revision of their target use in the educational process. it is a particular issue for interpretation of terms and concepts like “categories”, “patterns”, “attributes”, “means”, “approaches” which are extremely tangled and not systemized in accordance with the professional direction. This article makes a superficial analysis of sources on the basics of composition and morphogenesis, it establishes that the most problematic issue is that authors do not distinguish a planar composition as a separate type while considering characteristics of principles of morphogenesis. The article emphasizes that in the graphic design actions are held in a two-dimensional space, however, despite the lack of third dimension, all principles of morphogenesis take the place in the organization of planar composition. At the same time, it is emphasized that each task of graphic design has certain differences in the quantitative use of the patterns of composition. The article gives an example of the definition of priority principle of formation of integral groups within the plane, as well as one of the possible algorithms for creating a figurative font composition.

Water-resistant fiber-reinforced gypsum cement-pozzolanic composites

Gypsum and gypsum-cement-pozzolanic composites are of significant interest as materials and products for building decoration. The current tendency to reduce the consumption of gypsum-based materials and products in the context of growth and development of the finishing materials market depends on the decrease in their competitiveness compared to peers. This leads to significant interest in improving the quality of products based on gypsum and gypsum-cement-pozzolanic binder. Dispersed reinforcement is one of the ways of improving performance characteristics. The role of the type of reinforcing fibers in the formation of the gypsum-cement-pozzolanic composites structure and properties is studied in article. The influence relations of the cellulose fibers content with varying grinding degrees on the relative flexural and compressive strength of a gypsum-cement-pozzolanic matrix are obtained. It was found that the optimal content of cellulose fibers in the modified gypsum-cement-pozzolanic matrix is 0.5-1% by weight of the binder, the best indicators of flexural and compressive strength are achieved by grinding cellulose fibers to 30°SR. Using scanning electron microscopy, it was found that the microstructure of a disperse-reinforced gypsum-cementpozzolanic matrix is characterized by a uniform cellulose fibers distribution, the predominance of directionally frame reinforcement with a fibers linear orientation in the sheet plane. In this way the right choice of the type, crushing degree and cellulose fibers content can improve the quality and expand the application area of the produced gypsum-cementpozzolanic composites.

Microstructural Characterization of Mg-TM (TM=Ni or Cu) - Y Alloys and their Mechanical Property

Microstructure and mechanical property of the Mg-TM (TM=Ni or Cu) -Y alloys were investigated. Results revealed that Mg phase, Long period stacking ordered (LPSO) phase, and Mg2TM phase were formed in the Mg-TM-Y alloy around the composition ratios of TM and Y are 1:1 or 1:2. Tensile test clearly showed relationship between the mechanical property and microstructure in Mg-Ni-Y cast alloy. The 0.2% proof stress (σ0.2) of the Mg-Ni-Y cast alloy increase with the increasing solute elements contents, while the elongation decreases. This result indicated that the Mg-TM-Y alloy with the composition ratios of TM and Y are 1:1 or 1:2 have both high proof stress and appropriate elongation. It was suggested that the LPSO phase was appropriate strengthening phase in the Mg-rich region in the Mg-TM-Y alloy system. Basal texture of the LPSO and Mg phases was formed by hot-rolling in the sheet plane and the Mg2TM phase was dispersed in the Mg phase. The Mg97Cu1Y2 rolled sheet showed highσ0.2 about 350 MPa at room temperature. Furthermore, formation of an oxide film on the Mg-Cu-Y alloy was investigated at 973 K in air. As a result, it was suggested that the Y2O3 film was formed on the re-melted Mg-Cu-Y alloy surface as an incombustible oxide film.