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Grain Boundary Structure (grain + boundary_structure)
Selected AbstractsEnhanced Strength and Ductility of Ultrafine-Grained Ti Processed by Severe Plastic Deformation,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Irina Semenova This work deals with the study of strength and ductility in ultrafine-grained (UFG) Ti Grade 4 produced by equal channel angular pressing (ECAP) in combination with subsequent thermomechanical treatments. We found that additional annealing of UFG Ti resulted in unusual enhancement of strength and ductility, which is associated with not only small grain size but also with a grain boundary structure. The origin of this phenomenon is investigated using the results of transmission electron microscopy and atom probe tomography. The innovation potential of UFG Ti for medical use is considered. [source] First combined electron backscatter diffraction and transmission electron microscopy study of grain boundary structure of deformed quartziteJOURNAL OF MICROSCOPY, Issue 3 2006N. SHIGEMATSU Summary The structures of boundaries in a deformed and dynamically recovered and recrystallized quartz polycrystal (mylonite) were characterized by transmission electron microscopy, after the misorientation angles across the same grain boundaries had been analysed using electron backscatter diffraction in a scanning electron microscope. In this new approach, a specific sample area is mapped with electron backscatter diffraction, and the mapped area is then attached to a foil, and by the ion beam thinned for transmission electron microscopy analysis. Dislocations in grain boundaries were recognized as periodic and parallel fringes. The fringes associated with dislocations are observed in boundaries with misorientations less than 9°, whereas such fringes cannot be seen in the boundaries with misorientations larger than 17°. Some boundaries with misorientations between 9° and 17° generally have no structures associated with dislocation. One segment of a boundary with a misorientation of 13.5° has structures associated with dislocations. It is likely that the transition from low-angle to high-angle boundaries occurs at misorientations ranging from approximately 9° to 14°. Change in the grain boundary structure presumably influences the mobility of the boundaries. In the studied deformed quartz vein, a relative dearth of boundaries between misorientation angles of , = 2° and , = 15° has previously been reported, and high-angle boundaries form cusps where they intersect low-angle boundaries, suggesting substantial mobility of high-angle boundaries. [source] Superplasticity and high temperature deformation behaviour in nano grain Tungsten compactsMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4-5 2008K. Ameyama Abstract Nano grain tungsten is fabricated by Mechanical Milling (MM) process, and its grain growth behavior and high temperature deformability is investigated. As a result, a nano grain structure, whose grain size is approximately 20 nm or less, is obtained after MM for 360ks. Those nano grains demonstrate an irregular grain boundary structure, i.e., "non-equilibrium grain boundary", and they change to a smooth grain boundary structure by annealing at 1023 K for 3.6 ks. Compacts with nano grain structure indicate superior sintering property even at 1273 K (0.35 Tm). Rhenium addition prevents grain growth during sintering and thus the compacts indicate a further improvement in deformability. The compact is composed of equiaxed grain, whose grain size is 420 nm, and has low dislocation density even after the large deformation. The strain rate sensitivity, i.e., m-value, of 0.41 is obtained in the W-Re compact at 1473 K. Those results strongly imply that the nano grain W-Re compacts show superplasticity at less than half of the melting temperature, i.e., 1473 K (0.42 of the solidus temperature). [source] | ||||||||||