Grain Characteristics of 1235 Aluminum Alloy during Rolling

Grain characteristics of rolled 1235 aluminum alloy were studied by EBSD. The effects of hot rolling, cold rolling and rolling deformation on grain boundaries and grain size of the metal were studied as well. The content of high-angle boundaries was low by 16.48 % in 50 % hot-rolled 1235 aluminum alloy. The complete dynamic recrystallization occurred, and grains were coarse. During 90 % hot rolling, the low-angle boundaries turned into high-angle boundaries constantly. The content of high-angle boundaries was higher by 40.16 %. Coarse grains broke into fine grains, and grew into medium grains. In the 90 % cold-rolled alloy, the trace shape of high-angle boundary was irregular. The lattice distortion was large, providing the energy needed in recrystallization during recrystallization annealing.

Cube{100}<001> Grains Nucleation during Annealing of S-Oriented Aluminum Single Crystal

The crystallographic aspects of nucleation of cube grains during annealing have been analyzed in (234)[20-28 11] - oriented aluminum single crystal. The samples were plane strain compressed in a channel-die up to logarithmic strains of 0.5 (40%) and then annealed to develop initial and final stages of primary recrystallization. The deformed and annealed samples were analyzed using scanning electron microscopy equipped with EBSD facility. Local orientation measurements reveled that significant part of the sample deforms homogeneously with only small deviation from the initial crystal orientation. The heterogeneities were thin bands of localized strain in which the crystal lattice rotate towards another variant of S orientation. After annealing the orientations identified inside deformed/recovered areas were similar to that observed in the sample just after deformation. The crystal lattice of recrystallized grains exhibit a well-defined clockwise and anticlockwise rotations around the axes grouped near all normals of the {111} planes of the deformed/recovered state. The cube grains were observed in both homogeneously and heterogeneously deformed areas despite the cube-oriented nuclei surrounded by high angle boundary were not present in the as-deformed structure.

Dislocation Formation From a Polycrystal Free-Surface

The introduction of a dislocation from the free-surface of a grain A of a polycrystal has been investigated from the theoretical point of view. Assuming two disclination dipoles are lying in a high angle boundary separating the corresponding grain A and a neighbor grain B, the equilibrium position of the dislocation has been determined in the grain A versus the separation distance between the two dipoles, the length and strength of each dipole.

ANALYSIS OF HEAT TREATMENT EFFECT ON MICROSTRUCTURAL FEATURES EVOLUTION IN A MICRO-ALLOYED MARTENSITIC STEEL

<p>The microstructural evolution of a quenched and tempered medium-C micro-alloyed steel during tempering is analyzed The steel was heat treated in order to develop fully martensitic microstructures after quenching with different prior austenite grain sizes (AGS).</p><p>Main results can be summarized as below:</p><ul><li>A very poor effect of AGS on packet size is found.</li><li>High-angle boundary grains do not significantly grow after tempering; on the contrary, low-angle grain boundaries (cells) move, fully justifying the hardness evolution with tempering temperature. </li></ul>

Grain Boundary Dynamics under an Applied Stress

The response of various structurally different planar grain boundaries in aluminum bicrystals to an applied stress was experimentally investigated. Stress induced boundary migration was observed to be coupled to a tangential translation of the grains for symmetrical and asymmetrical and tilt boundaries with both low and high misorientation angles. The activation enthalpy of high angle boundary migration was found to vary non-monotonously with misorientation angle, whereas for low angle boundaries the migration activation enthalpy was virtually the same. The Σ7 CSL boundaries in bicrystals of different geometry were observed to move under an applied stress, but their migration did not produce shear. These crystallographically equivalent boundaries, however, were found to behave different with respect to migration rate and its temperature dependence. The stress driven migration of the mixed tilt-twist boundary was observed to be accompanied by both the translation of adjacent grains parallel to the boundary plane and their rotation around the boundary plane normal. This behavior was interpreted in terms of the structure of the investigated tilt-twist boundary.

New Type of Ultra-Fine Grained Microstructure in Ti-6Al-4V Alloy for Enhancing Superplasticity

This work presents a formation of ultrafine-grained microstructure (d ~ 0.2 μm) with high fraction of high-angle boundary in industrial Ti–6Al–4V alloy produced by the hot compression of a sample with the acicular α′martensite starting microstructure . It is found that heterogeneous nucleation becomes dominant in the case of the α’ starting microstructure.α

Loss of High Angle Boundary Area during Annealing a Cryo-SPD Processed Al-Alloy with a Nano-Scale Lamellar Grain Structure

The grain structure and texture evolution during annealing an Al-0.13%Mg submicron grained alloy, deformed by plane strain compression (PSC) at cryogenic temperatures, has been investigated. On annealing the grain structure coarsened and transformed from lamellar to equiaxed. But, remarkably, the fraction of low angle boundaries (LABs) increased, from less than ~ 25% to ~50% above 300 °C, leading to instability and discontinuous coarsening at higher temperatures. The surprisingly large increase in LAB fraction on annealing is shown to be related to orientation impingement originating from the strong texture present after PSC in liquid nitrogen.

Microstructure and Texture Evolution during Equal Channel Angular Extrusion of Pure Copper: Effect of Strain Rat

Effect of strain velocity on the refinement of severe plastic deformation structure of ECA pressed pure copper was studied using transmission electron microscope(TEM) and electron back-scattered diffraction (EBSD) analysis. Formation mechanism of unltra-fine grain with high angle boundary was discussed. It was found that exceedingly fast stain rate can significantly increase the fraction of high angle boundary, up to 76%, and make grain refine further, up to 0.23μm.

Texture and High-Angle Boundary Formation during Deformation Processing

Among the phenomena leading to formation of high-angle boundaries during deformation processing at low homologous temperatures is the subdivision of prior grains and formation of deformation bands. Evidence for this phenomenon during processing of AA2004, a superplastic aluminum alloy, is reviewed; fragmentation of deformation bands leads to equiaxed grains and high-angle boundaries that support superplasticity. In addition to subdivision, groups of grains undergo lattice rotation toward one or the other variant of the β orientation fibers during plane-strain deformation of pure aluminum by ambient temperature rolling. The formation of equiaxed grains from banded structures during simple shear by equal channel angular pressing (ECAP) is also considered.