• Journal of Powder Materials
• /
• v.18 no.2
• /
• pp.168-171
• /
• 2011

We investigate grain growth behavior of poly-crystalline Mg sheet having strong basal fiber texture using phase field model for grain growth and micro-elasticity. Strong initial basal texture was maintained when external load was not imposed, but was weaken when external biaxial strain was imposed. Elastic interaction between elastic anisotropy of Mg grain and external load is the reason why texture evolution occurs.

• Korean Journal of Metals and Materials
• /
• v.47 no.6
• /
• pp.356-362
• /
• 2009

In order to vary the primary recrystallization textures, AA 1050 sheets were cold rolled in two different manners. Differences in cold rolling schedule gave rise to the formation of different cold rolling textures also leading to the formation of different primary recrystallization textures. Upon annealing for grain growth, changes in microstructure and texture hardly occurred in the sample depicting Cube recrystallization texture, while grain growth was accompanied with the development {001}<100> Cube texture in the sample displaying a recrystallization texture comprising of weak rolling texture components. The selective growth of Cube oriented grains is attributed to the high mobility of their grain boundaries.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.05a
• /
• pp.57-58
• /
• 2006

The effects of lowering ECAP temperature during ECAP process and Post-ECAP annealing on microstructure, texture and mechanical properties of the AZ31 alloys have been investigated in the present study. The as-extruded materials were ECAP processed to 2 passes at 553K prior to subsequent pressing up to 6 passes at 523K or 493K. When this method of lowering ECAP temperature during ECAP was used, the rods could be successfully deformed up to 6 passes without any surface cracking. Grain refinement during ECAP process at 553K might have helped the material to endure further straining at lower deformation temperatures probably by increasing the strain accommodation effect by grain boundary sliding, causing stress relaxation. Texture modification during ECAP has a great influence on the strength of Mg alloys because HCP metals have limited number of slip systems. As slip is most prone to take place on basal planes in Mg at room temperature, the rotation of high fraction of basal planes to the directions favorable for slip as in ECAP decreases the yield stress appreciably. The strength of AZ31 Mg alloys increases with decrease of grain size if the texture is constant though ECAP deformation history is different. A standard positive strength dependence on the grain size for Mg alloys with the similar texture (Fig. 1) supports that the softening of ECAPed Mg alloys (a negative slope) typically observed despite the significant grain refinement is due to the texture modification where the rotation of basal planes occurs towards the orientation for easier slip. It could be predicted that if the original fiber texture is restored after ECAP treatment yielding marked grain refinement, yield stress as high as 500 MPa will be obtained at the grain size of ${\sim}1{\mu}m$. Differential speed rolling (DSR) with a high speed ratio between the upper and lower rolls was applied to alter the microstructure and texture of the AZ31 sheets. Significant grain refinement took place during the rolling owing to introduction of large shear deformation. Grain size as small as $1.4{\mu}m$ could be obtained at 423K after DSR. There was a good correlation between the (0002) pole intensity and tensile elongation. This result indicates that tensile ductility improvement in the asymmetrically rolled AZ31 Mg alloys is closely related to the weakening of basal texture during DSR. Further basal texture weakening occurred during annealing after DSR. According to Hall-Petch relation shown in Fig. 1, the strength of the asymmetrically rolled AZ31 is lower than that of the symmetrically rolled one when compared at the same grain size. This result was attributed to weakening of fiber texture during DSR. The DSRed AZ31, however, shows higher strength than the ECAPed AZ31 where texture has been completely replaced by a new texture associated with high Schmid factors.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.02a
• /
• pp.81-84
• /
• 2003

The effect of annealing condition on the texture and microstructure development in Ni tapes fabricated by cold-rolling including powder metallurgy was investigated. The Pole-figure results showed that the Ni tapes annealed at lower temperature than 50$0^{\circ}C$ were the mixture of brass deformation texture and cube texture. The specimens annealed at high temperatures had only well-developed cube texture and the FWHMs of in-plane and out-of-plane were in the range of 8-10$^{\circ}$. The degree of texture was not significantly depended on annealing temperatures. The grain morphologies of Ni tapes prepared at low temperatures showed serrated grain boundaries due to incomplete recrystallization, but the specimens prepared at high temperatures showed stabilized grain shape without serrated grain boundaries.

• Journal of Magnetics
• /
• v.15 no.1
• /
• pp.32-35
• /
• 2010

The effects of Cu-addition and die-upset temperature on the texture in the die-upset Nd-lean $Nd_xFe_{93.5-(x+y)}-Cu_yGa_{0.5}B_6$ (x = 9-12, y = 0-2) alloys were investigated. The die-upset Cu-containing Nd-lean $Nd_{12}Fe_{81.5-y}-Cu_yGa_{0.5}B_6$ (y = 1, 2) alloys showed a considerable texture. Texture in the Nd-lean alloys developed through basal plane slip deformation. The Cu-addition reduced the melting point of grain boundary phase facilitating grain gliding during the die-upsetting, and providing a greater chance for the $Nd_2Fe_{14}B$ grains to meet the deformation conditions. Die-upsetting at higher temperature facilitated grain gliding and plastic deformation, thus enhancing texture.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.10
• /
• pp.938-945
• /
• 2003

We fabricated Ni-substrate for YBCO coated conductors and evaluated the effects of pressing and annealing temperature and time on texture. Ni substrate was fabricated by powder metallurgy technique and compacts were prepared by applying uniaxial or isostatic pressure. The texture of substrate made by applying cold isostatic pressure (CIP) was stronger than that by uniaxial pressure which we attribute to the fact that the CIP method provided higher density and more uniform density distribution. It was observed that the substrate annealed at 400 C showed both retained texture and recrystallized texture. On the other hand, the texture of substrate significantly improved at annealing temperature above 500 C, forming strong 4-fold symmetry, [111] II ND texture, and FWHM of 9∼10 . It is to be noted that the degree of texture was almost independent of annealing temperature (500∼1000 C) and annealing time(1∼54 min, at 1000 C). EBSD and AFM analysis indicated that 99% of grain boundaries was low angle grain boundary and RMS was approximately 3 nm, respectively. Development of strong cube texture and high fraction of low angle grain boundary of Ni-substrate made by powder metallurgy technique in our study is considered to be suitable for the application of YBCO coated conductors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.6
• /
• pp.499-504
• /
• 2001

We evaluated the degree of texture through depth of the superconductor core of Bi-Sr-Ca-Cu-O(BSCCO) superconductor tape. The degree of texture was characterized by pole figure analysis indicating that the degree of texture varied significantly with depth of the superconductor core. It was observed that the degree of texture was higher near the interface than inside the superconductor core. Specifically, as getting near to the center from the sheath/core interface, the orientation of BSCCO became dispersed from normal direction(ND) which, in turn, resulted in the degradation of <001>-fiber texture. In addition, the <001> texture was non-uniform an, better texture was developed along rolling direction(RD), compared to transverse direction(TD). Microstructural investigation showed that grain alignment was locally degraded by the existence of second phases. I was observed that larger grain size and better texturing were developed near the relatively straight interface compared to those inside the superconducting core. Based on our study, the region near the interface is thought to carry significant current compared to that inside the core.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.05a
• /
• pp.408-410
• /
• 2008

The evolution of texture and microstructure during recrystallization was tracked after different cold rolling of aluminum sheets. Texture of the sheet center were differentiated by different strain states due to prior deformation. The evolution of recrystallization texture was studied with the amount of shear applied during cold rolling. The final grain size after recrystallization annealing was varied due to the effective strain during deformation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2001.11a
• /
• pp.55-62
• /
• 2001

An electrolytic copper rod was drawn up to $90\%$ in area reduction and annealed under various conditions. The EBSD measurement of the drawn wire showed that in the center region the <111> + <100> fiber duplex texture was dominant, while in the middle and surface regions relatively defused textures developed with a little higher density in <11w>//wire axis. The inhomogeneous texture in the deformed wire gave rise to the inhomogeneous microstructure and texture after annealing. The annealing texture could be classified into the recrystallization texture developed during low temperatures and at the early stage at a high temperature and the growth texture developed after a prolonged annealing at the high temperature. The recrystallization temperature could be explained by the strain energy release maximization model and the growth texture was discussed based on the grain boundary mobility anisotropy.

• Economic and Environmental Geology
• /
• v.19 no.spc
• /
• pp.227-237
• /
• 1986

The Duk-Eum mine located in Kongsan-myeon, Naju-gun, Cheolanamdo is producing silver ore mainly, with rare gold association. The grade-up and recovery of the concentrates have been concerned to the main problem. And then, this study aimed at applying the basic data for ore processing. In the first half of the study, the attempts were made to identify the ore minerals, this followed by determination of the mineral texture, paragenesis, grain size, and size distribution by employing the microscopical method and the etching test. The results of the study are as follows: 1. The ore deposit is composed of the hydrothermal fissure linked veins, and filling cavities are mostly tensile fractures or joints, in rhyolitic rocks as a wall rock. 2. The principle ore minerals are native silver, acanthite, canfieldite, pyrargyrite, galena, tetrahedrite, sphalerite, pyrrhotite, chalcopyrite, chalcocite, covellite, zincite, and the gangue minerals are quartz and calcite. 3. The grain size of each ore minerals before grinding are; max. $2\frac{1}{2}$ mesh, medium 48-100 mesh(main size, contained over 80%), min. 3200mesh. And the grain size of each ore minerals after grinding is; max. 42mesh, medium 65-250mesh(main size, contained over 80%), min. 3200mesh. 4. The properties of the mineral texture effected on the ore dressing are follows; a) Inclusion texture; the fine grains of chalcopyrite is included in most acanthite, and rarely, that of galena included in acanthite. b) Exsolution texture; pyrargyrite is exsolved in acanthite. c) Replacement texture; native silver replaced pyrargyrite, and acanthite replaced galena. d) Interlocking paragenetic texture; the interlocking paragenetic minerals are pyrite, chalcopyrite, chalcocite, canfieldite. e) Fissure filling texture; chalcopyrite was filled along the cracks in acanthite. Among of the above texture, it is impossible to liberate the grains of a), and more difficult to liberate those of b) and c), while easy to liberate those of d) and e).