High Strain Monotonic Deformation-Structure and Strength

Microstructure, Texture and Deformation Mechanism of Zr702 Processed by Equal Channel Angular Pressing (ECAP)

Materials Science Forum ◽

10.4028/www.scientific.net/msf.503-504.533 ◽

2006 ◽

Vol 503-504 ◽

pp. 533-538

Author(s):

W.Q. Cao ◽

Seng Ho Yu ◽

Sun Keun Hwang ◽

Brigitte Bacroix

Keyword(s):

Deformation Mechanism ◽

High Strain ◽

Subgrain Size ◽

Rolling Texture ◽

X Rays ◽

Deformation Structure ◽

High Angle ◽

Electron Backscattered Diffraction ◽

Angular Pressing ◽

The Stability

The commercial purity zirconium (Zr702) has been deformed by Equal Channel Angular Press (ECAP) up to eight passes using route A and BC. The deformation microstructure and the bulk texture have been characterized by Electron Backscattered Diffraction (EBSD) in SEM and X-rays diffraction (XRD), respectively. The homogeneously lamellar deformation structure in route A and the equiaxed deformation structure with local heterogeneity in route BC have both been determined. In both cases the subgrain size flattened at about 0.33 ìm after 2 passes but average misorientation increased with increasing strain. After 8 passes high angle fraction is over 70% both in route A and route BC. The bimodal {0002} pole texture (high strain rolling texture) in route A and the strong unimodal {0002} pole texture with weak high strain rolling texture in route BC have been identified. The boundary texture has been analysed both in sample frame and crystallographic frame. It was found in sample frame that the boundary texture of high angle boundaries developed gradually in route A and more strongly than that in route BC, implying that the boundary characters evolved from the mixed characters (tilted and twist) to tilted boundary in route A. Based on the deformation structures and the bulk textures, the deformation mechanism of large local orientation rotation and the stability of the dislocation structures have been proposed to interpret the grain refinement and the texture development of Zr702 during ECAE processing.

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Solid Solution Effects and Deformation Micros trueture of Shock-Loaded Iron Manganese Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069090 ◽

1970 ◽

Vol 28 ◽

pp. 420-421

Author(s):

A. Christou ◽

J. V. Foltz ◽

N. Brown

Keyword(s):

Solid Solution ◽

Shock Loading ◽

High Strain ◽

Local Stress ◽

Strain Rates ◽

Local Stress Concentration ◽

Bcc Metals ◽

Manganese Alloys ◽

Iron Manganese ◽

Transmission Microscope

In general, all BCC transition metals have been observed to twin under appropriate conditions. At the present time various experimental reports of solid solution effects on BCC metals have been made. Indications are that solid solution effects are important in the formation of twins. The formation of twins in metals and alloys may be explained in terms of dislocation mechanisms. It has been suggested that twins are nucleated by the achievement of local stress-concentration of the order of 15 to 45 times the applied stress. Prietner and Leslie have found that twins in BCC metals are nucleated at intersections of (110) and (112) or (112) and (112) type of planes.In this paper, observations are reported of a transmission microscope study of the iron manganese series under conditions in which twins both were and were not formed. High strain rates produced by shock loading provided the appropriate deformation conditions. The workhardening mechanisms of one alloy (Fe - 7.37 wt% Mn) were studied in detail.

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Plastic Deformation in Microtomed Sections

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100066346 ◽

1971 ◽

Vol 29 ◽

pp. 458-459

Author(s):

J. Temple Black

Keyword(s):

Plastic Deformation ◽

Plastic Strain ◽

Applied Stress ◽

Elastic Strain ◽

High Strain ◽

Tool Material ◽

Cutting Edge ◽

Material Structure ◽

Geometrical Constraints

The output of the ultramicrotomy process with its high strain levels is dependent upon the input, ie., the nature of the material being machined. Apart from the geometrical constraints offered by the rake and clearance faces of the tool, each material is free to deform in whatever manner necessary to satisfy its material structure and interatomic constraints. Noncrystalline materials appear to survive the process undamaged when observed in the TEM. As has been demonstrated however microtomed plastics do in fact suffer damage to the top and bottom surfaces of the section regardless of the sharpness of the cutting edge or the tool material. The energy required to seperate the section from the block is not easily propogated through the section because the material is amorphous in nature and has no preferred crystalline planes upon which defects can move large distances to relieve the applied stress. Thus, the cutting stresses are supported elastically in the internal or bulk and plastically in the surfaces. The elastic strain can be recovered while the plastic strain is not reversible and will remain in the section after cutting is complete.

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Investigation of shock-wave deformation history from recovered structure

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143754 ◽

1986 ◽

Vol 44 ◽

pp. 434-435

Author(s):

M.A. Mogilevsky ◽

L.S. Bushnev

Keyword(s):

Shock Wave ◽

Plastic Deformation ◽

Dislocation Density ◽

Shock Waves ◽

Shock Front ◽

Single Crystals ◽

Residual Deformation ◽

Deformation Structure ◽

Deformation History ◽

Deformation Velocity

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.

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