Texture Evolution in Severe Plastic Deformation Processes

During severe plastic deformation (SPD), there is usually extended grain fragmentation, associated with the formation of a crystallographic texture. The effect of texture evolution is, however, coarsening in grain size, as neighbor grains might coalesce into one grain by approaching the same ideal orientation. This work investigates the texture-induced grain coarsening effect in face-centered cubic polycrystals during simple shear, in 3D topology. The 3D polycrystal aggregate was constructed using a cellular automaton model with periodic boundary conditions. The grains constituting the polycrystal were assigned to orientations, which were updated using the Taylor polycrystal plasticity approach. At the end of plastic straining, a grain detection procedure (similar to the one in electron backscatter diffraction, but in 3D) was applied to detect if the orientation difference between neighboring grains decreased below a small critical value (5°). Three types of initial textures were considered in the simulations: shear texture, random texture, and cube-type texture. The most affected case was the further shearing of an initially already shear texture: nearly 40% of the initial volume was concerned by the coalescence effect at a shear strain of 4. The coarsening was less in the initial random texture (~30%) and the smallest in the cube-type texture (~20%). The number of neighboring grains coalescing into one grain went up to 12. It is concluded that the texture-induced coarsening effect in SPD processing cannot be ignored and should be taken into account in the grain fragmentation process.

Download Full-text

Constitutive Equations for Severe Plastic Deformation Processes

Conference Proceedings of the Society for Experimental Mechanics Series - Mechanics of Composite and Multi-functional Materials, Volume 7 ◽

10.1007/978-3-319-41766-0_9 ◽

2016 ◽

pp. 73-79

Author(s):

Robert Goldstein ◽

Sergei Alexandrov ◽

Marko Vilotic

Keyword(s):

Plastic Deformation ◽

Severe Plastic Deformation ◽

Constitutive Equations ◽

Deformation Processes

Download Full-text

Prediction of the Stress-Strain Response of the Ultrafine-Grained Materials Using Multi-Scale Analysis

ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels: Parts A and B ◽

10.1115/fedsm-icnmm2010-30871 ◽

2010 ◽

Author(s):

Mihaela Banu ◽

Mitica Afteni ◽

Alexandru Epureanu ◽

Valentin Tabacaru

Keyword(s):

Plastic Deformation ◽

Grain Size ◽

Aluminum Alloy ◽

Severe Plastic Deformation ◽

Scale Analysis ◽

Multi Scale ◽

Ultrafine Grained ◽

Deformation Processes ◽

Ultrafine Grained Materials ◽

Multi Scale Analysis

There are several severe plastic deformation processes that transform the material from microsized grains to the nanosized grains under large deformations. The grain size of a macrostructure is generally 300 μm. Following severe plastic deformation it can be reached a grain size of 200 nm and even less up to 50 nm. These structures are called ultrafine grained materials with nanostructured organization of the grains. There are severe plastic deformation processes like equal angular channel, high pressure torsion which lead to a 200 nm grain size, respectively 100 nm grain size. Basically, these processes have a common point namely to act on the original sized material so that an extreme deformation to be produced. The severe plastic deformation processes developed until now are empirically-based and the modeling of them requires more understanding of how the materials deform. The macrostructural material models do not fit the behavior of the nanostructured materials exhibiting simultaneously high strength and ductility. The existent material laws need developments which consider multi-scale analysis. In this context, the present paper presents a laboratory method to obtain ultrafine grains of an aluminum alloy (Al-Mg) that allows the microstructure observations and furthermore the identification of the stress–strain response under loadings. The work is divided into (i) processing of the ultrafine-grained aluminum alloy using a laboratory-scale process named in-plane controlled multidirectional shearing process, (ii) crystallographic analysis of the obtained material structure, (iii) tensile testing of the ultrafine-grained aluminum specimens for obtaining the true stress-strain behavior. Thus, the microscale phenomena are explained with respect to the external loads applied to the aluminum alloy. The proposed multi-scale analysis gives an accurate prediction of the mechanical behavior of the ultrafine-grained materials that can be further applied to finite element modeling of the microforming processes.

Download Full-text

Upgrading Property of A-Fe Alloys through the Microstructure Refinement by Compressive Torsion Processing

Materials Science Forum ◽

10.4028/www.scientific.net/msf.794-796.802 ◽

2014 ◽

Vol 794-796 ◽

pp. 802-806 ◽

Cited By ~ 1

Author(s):

Yuji Kume ◽

Shinichiro Ota ◽

Makoto Kobashi ◽

Naoyuki Kanetake

Keyword(s):

Plastic Deformation ◽

Severe Plastic Deformation ◽

Tensile Properties ◽

Grain Refinement ◽

Deformation Process ◽

Room Temperature ◽

Plastic Deformation Process ◽

Deformation Processes ◽

Alloy Microstructure ◽

Fe Alloys

Cast AlFe alloys containing several percent iron have low ductility because of their brittle precipitates. Therefore, precipitate refinement is very important for improving their mechanical properties. In recent decades, severe plastic deformation processes have been developed to achieve this grain refinement. For example, our previously proposed severe plastic deformation process, called compressive torsion, is quite effective for not only grain refinement but also precipitate refinement even in brittle materials. In the present work, precipitate refinement of cast Al—Fe alloys by compressive torsion and the resulting improvements in their tensile properties were investigated. Compressive torsion with various numbers of revolutions was applied to Al—Fe alloys at 373 K. Then, the alloys were subjected to tensile testing at room temperature, 473 K, and 573 K. The obtained experimental results indicated that the initial eutectic microstructure of the alloys disappeared after the compressive torsion processing. All large precipitates with sizes of more than 200 μm were refined, and their sizes were reduced to several tens of micrometers. Furthermore, these refined precipitates were dispersed homogenously in the alloy microstructure. In result, the tensile properties of the alloys, namely, their strength and elongation, were improved remarkably. In particular, the elongation reached more than 30% at room temperature.

Download Full-text