Disorientations after Severe Plastic Deformation and their Effect on Work-Hardening

2010 ◽  
Vol 667-669 ◽  
pp. 205-210 ◽  
Author(s):  
W. Pantleon
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Work Hardening ◽  
High Pressure Torsion ◽  
Dislocation Dynamics ◽  
Plastic Strains ◽  
Different Types ◽  
Disorientation Angle ◽  
Experimental Findings ◽  
Crystalline Symmetry

Plastic deformation creates orientation differences in grains of originally uniform orientation. These disorientations are caused by a local excess of dislocations having the same sign of the Burgers vector. Their increase with increasing plastic strain is modeled by dislocation dynamics taking into account different storage mechanisms. The predicted average disorientation angles across different types of boundaries are in close agreement with experimental data for small and moderate plastic strains. At large plastic strains after severe plastic deformation, saturation of the measured average disorientation angle is observed. This saturation is explained as an immediate consequence of the restriction of experimentally measured disorientation angles to angles below a certain maximum value imposed by crystalline symmetry. Taking into account the restrictions from crystalline symmetry for modeled disorientation angles does not only lead to an excellent agreement with experimental findings on Ni after high pressure torsion, but also rationalizes the work-hardening behavior at large plastic strains as well as a saturation of the flow stress.

Structure and Properties of Mg-Al-Ca Alloy after Severe Plastic Deformation

2008 ◽  
Vol 584-586 ◽  
pp. 559-564 ◽  
Author(s):  
Sergey V. Dobatkin ◽  
Yuri Estrin ◽  
L.L. Rokhlin ◽  
Mikhail V. Popov ◽  
Rimma Lapovok ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
High Pressure Torsion ◽  
Nanocrystalline Structure ◽  
Grain Structure ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Different Types ◽  
Lower Temperature

Severe plastic deformation of a Mg-Al-Ca alloy resulted in different types of grain structure. High pressure torsion (HPT) was shown to lead to the formation of a nanocrystalline structure with a grain size of 100-200 nm, while equal channel angular pressing (ECAP) produced ultrafine grained (UFG) or submicrocrystalline (SMC) structures, depending on the ECAP temperature. An UFG structure with a grain size of 2-5 -m was formed at 300°C, as distinct from a finer SMC structure with a grain size of 300-800 nm formed at a lower temperature (220°C). The possibility of increasing the strength of the alloy in the UFG condition by a factor of 1.5-2, combined with a reasonable level of ductility and enhanced functional properties was thus demonstrated. ECAP of annealed Mg-Al-Ca with the formation of UFG structure was shown to lead to increased yield strength (by a factor of 2) and enhanced tensile ductility (by a factor of 3).

Deformation Behaviour and Ultrafine Grained Structure Development in Steels with Different Carbon Content Subjected to Severe Plastic Deformation

2007 ◽  
Vol 345-346 ◽  
pp. 45-48 ◽  
Author(s):  
Jozef Zrník ◽  
Sergey V. Dobatkin ◽  
Ondrej Stejskal
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Work Hardening ◽  
Favourable Effect ◽  
Tensile Behaviour ◽  
Dislocation Network ◽  
Strength Increase ◽  
Subgrain Structure ◽  
Low Carbon ◽  
Channel Angle

The article focuses on the results from recent experimental of severe plastic deformation of low carbon (LC) steel and medium carbon (MC) steel performed at increased temperatures. The grain refinement of ferrite respectively ferrite-pearlite structure is described. While LC steel was deformed by ECAP die (ε = 3) with a channel angle φ = 90° the ECAP severe deformation of MC steel was conducted with die channel angle of 120° (ε = 2.6 - 4). The high straining in LC steel resulted in extensively elongated ferrite grains with dense dislocation network and randomly recovered and polygonized structure was observed. The small period of work hardening appeared at tensile deformation. On the other side, the warm ECAP deformation of MC steel in dependence of increased effective strain resulted in more progressive recovery process. In interior of the elongated ferrite grains the subgrain structure prevails with dislocation network. As straining increases the dynamic polygonization and recrystallization became active to form mixture of polygonized subgrain and submicrocrystalline structure. The straining and moderate ECAP temperature caused the cementite lamellae fragmentation and spheroidzation as number of passes increased. The tensile behaviour of the both steels was characterized by strength increase however the absence of strain hardening was found at low carbon steel. The favourable effect of ferrite-pearlite structure modification due straining was reason for extended work hardening period observed at MC steel.

Disorientations in dislocation structures: Formation and spatial correlation

2002 ◽  
Vol 17 (9) ◽  
pp. 2433-2441 ◽  
Author(s):  
Wolfgang Pantleon
Keyword(s):  
Plastic Deformation ◽  
Spatial Correlation ◽  
Distribution Functions ◽  
Scaling Behavior ◽  
Dislocation Dynamics ◽  
Slip Systems ◽  
Experimental Findings ◽  
Good Agreement

During plastic deformation, dislocation boundaries are formed and orientation differences across them arise. Two different causes lead to the formation of two kinds of deformation-induced boundaries: a statistical trapping of dislocations in incidental dislocation boundaries and a difference in the activation of slip systems on both sides of geometrically necessary boundaries. On the basis of these mechanisms, the occurrence of disorientations across both types of dislocation boundaries is modeled by dislocation dynamics. The resulting evolution of the disorientation angles with strain is in good agreement with experimental observations. The theoretically obtained distribution functions for the disorientation angles describe the experimental findings well and explain their scaling behavior. The model also predicts correlations between disorientations in neighboring boundaries, and evidence for their existence is presented.

scholarly journals The Effect of the In-Situ Heat Treatment on the Martensitic Transformation and Specific Properties of the Fe-Mn-Si-Cr Shape Memory Alloys Processed by HSHPT Severe Plastic Deformation

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4621
Author(s):  
Carmela Gurau ◽  
Gheorghe Gurau ◽  
Felicia Tolea ◽  
Bogdan Popescu ◽  
Mihaela Banu ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
High Speed ◽  
High Pressure Torsion ◽  
Electron Interaction ◽  
Sudden Increase ◽  
Neel Temperature ◽  
Néel Temperature

This work focuses on the temperature evolution of the martensitic phase ε (hexagonal close packed) induced by the severe plastic deformation via High Speed High Pressure Torsion method in Fe57Mn27Si11Cr5 (at %) alloy. The iron rich alloy crystalline structure, magnetic and transport properties were investigated on samples subjected to room temperature High Speed High Pressure Torsion incorporating 1.86 degree of deformation and also hot-compression. Thermo-resistivity as well as thermomagnetic measurements indicate an antiferromagnetic behavior with the Néel temperature (TN) around 244 K, directly related to the austenitic γ-phase. The sudden increase of the resistivity on cooling below the Néel temperature can be explained by an increased phonon-electron interaction. In-situ magnetic and electric transport measurements up to 900 K are equivalent to thermal treatments and lead to the appearance of the bcc-ferrite-like type phase, to the detriment of the ε(hcp) martensite and the γ (fcc) austenite phases.

Role of Strain Gradient and Dynamic Transformation on the Formation of Nanocrystalline Structure Produced by Severe Plastic Deformation

2007 ◽  
Vol 539-543 ◽  
pp. 2787-2792 ◽  
Author(s):  
Minoru Umemoto ◽  
Yoshikazu Todaka ◽  
Jin Guo Li ◽  
Koichi Tsuchiya
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Refinement ◽  
Strain Gradient ◽  
High Pressure Torsion ◽  
Large Strain ◽  
Nanocrystalline Structure ◽  
Angular Pressing ◽  
Dynamic Transformation ◽  
Fine Grained Structure

Formation of nanocrystalline structure by severe plastic deformation has studied extensively. Although ultra fine grained structure (grain size larger than 100 nm) had been obtained in many processes such as heavy cold rolling, equal channel angular pressing (ECAP) or accumulative roll bonding (ARB), the formation of nano grained structure (< 100 nm) is limited to processes such as ball milling, shot peening or drilling. In the present study, high pressure torsion (HPT) deformation and drilling were carried out to understand the conditions necessary to obtain nano grained structure in steels. The results of HPT experiments in pure Fe showed that HPT has superior ability of strengthening and grain refinement probably due to a strain gradient but the saturation of grain refinement occurs before reaching nano grained structure. Drilling experiments in high carbon martensitic steel revelaed that nano grained ferrite forms at the drilled hole surface only when the transformation from ferrite to austenite takes place during drilling. Considering various other processes by which nano grained ferrite was produced, it is proposed that heavy strains with large strain gradients together with dynamic transformation are necessary to reach nano grained ferrite structure.

Structure and Thermal Stability of Cu after Severe Plastic Deformation

2010 ◽  
Vol 297-301 ◽  
pp. 1312-1321 ◽  
Author(s):  
Vladimir V. Popov ◽  
A.V. Stolbovkiy ◽  
E.N. Popova ◽  
V.P. Pilyugin
Keyword(s):  
Thermal Stability ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
High Pressure Torsion ◽  
Pure Copper ◽  
Nanocrystalline Structure ◽  
Transmission Electron ◽  
Evolution Of Structure ◽  
Stability Of Structure ◽  
Thermal Stability Of

Evolution of structure of high-purity and commercially pure copper at severe plastic deformation (SPD) by high pressure torsion (HPT) at room temperature and in liquid nitrogen has been studied by transmission electron microscopy (TEM) and measurements of microhardness. Thermal stability of structure obtained by HPT has been investigated. Factors preventing from obtaining nanocrystalline structure in Cu are analyzed and possible ways of their overcoming are discussed.

scholarly journals Crystallization Features of Amorphous Rapidly Quenched High Cu Content TiNiCu Alloys upon Severe Plastic Deformation

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2670
Author(s):  
Alexander Glezer ◽  
Nikolay Sitnikov ◽  
Roman Sundeev ◽  
Alexander Shelyakov ◽  
Irina Khabibullina
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Copper Content ◽  
Melt Spinning ◽  
High Pressure Torsion ◽  
Amorphous State ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Cu Content ◽  
Rapid Melt Quenching

In recent years, the methods of severe plastic deformation and rapid melt quenching have proven to be an effective tool for the formation of the unique properties of materials. The effect of high-pressure torsion (HPT) on the structure of the amorphous alloys of the quasi-binary TiNi–TiCu system with a copper content of more than 30 at.% produced by melt spinning technique has been analyzed using the methods of scanning electron microscopy, X-ray diffraction analysis, and differential scanning calorimetry (DSC). The structure examinations have shown that the HPT of the alloys with a Cu content ranging from 30 to 40 at.% leads to nanocrystallization from the amorphous state. An increase in the degree of deformation leads to a substantial change in the character of the crystallization reflected by the DSC curves of the alloys under study. The alloys containing less than 34 at.% Cu exhibit crystallization peak splitting, whereas the alloys containing more than 34 at.% Cu exhibit a third peak at lower temperatures. The latter effect suggests the formation of regions of possible low-temperature crystallization. It has been established that the HPT causes a significant decrease in the thermal effect of crystallization upon heating of the alloys with a high copper content relative to that of the initial amorphous melt quenched state.

scholarly journals Tuneable Magneto-Resistance by Severe Plastic Deformation

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1188 ◽  
Author(s):  
Stefan Wurster ◽  
Lukas Weissitsch ◽  
Martin Stückler ◽  
Peter Knoll ◽  
Heinz Krenn ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
High Pressure Torsion ◽  
Processing Parameters ◽  
Ferromagnetic Phase ◽  
Room Temperature Resistivity ◽  
Small Particles ◽  
Bulk Specimen ◽  
Binary Powder Mixtures ◽  
Magneto Resistance

Bulk metallic samples were synthesized from different binary powder mixtures consisting of elemental Cu, Co, and Fe using severe plastic deformation. Small particles of the ferromagnetic phase originate in the conductive Cu phase, either by incomplete dissolution or by segregation phenomena during the deformation process. These small particles are known to give rise to granular giant magneto-resistance. Taking advantage of the simple production process, it is possible to perform a systematic study on the influence of processing parameters and material compositions on the magneto-resistance. Furthermore, it is feasible to tune the magneto-resistive behavior as a function of the specimens’ chemical composition. It was found that specimens of low ferromagnetic content show an almost isotropic drop in resistance in a magnetic field. With increasing ferromagnetic content, percolating ferromagnetic phases cause an anisotropy of the magneto-resistance. By changing the parameters of the high pressure torsion process, i.e., sample size, deformation temperature, and strain rate, it is possible to tailor the magnitude of giant magneto-resistance. A decrease in room temperature resistivity of ~3.5% was found for a bulk specimen containing an approximately equiatomic fraction of Co and Cu.

Structure and Properties of Grain Boundaries in Submicrocrystalline W Obtained by Severe Plastic Deformation

2009 ◽  
Vol 283-286 ◽  
pp. 629-638 ◽  
Author(s):  
Vladimir V. Popov ◽  
Ruslan Valiev ◽  
E.N. Popova ◽  
A.V. Sergeev ◽  
A.V. Stolbovsky ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Plastic Deformation ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
High Pressure Torsion ◽  
Submicrocrystalline Structure ◽  
Emission Mössbauer Spectroscopy ◽  
Structure And Properties ◽  
Initial State

Submicrocrystalline structure of W obtained by severe plastic deformation (SPD) by high pressure torsion (5 revolutions of anvils at 4000C) and its thermal stability have been examined by TEM. Grain boundaries of submicrocrystalline W have been studied by the method of the emission Mössbauer spectroscopy in the initial state and after annealing at 400-6000С.

Sign in / Sign up

Export Citation Format

Share Document