Influence of Deformation on Precipitation Kinetics in Mg-Tb Alloy

2012 ◽  
Vol 322 ◽  
pp. 151-162 ◽  
Author(s):  
Oksana Melikhova ◽  
Jakub Čížek ◽  
Petr Hruška ◽  
Marián Vlček ◽  
Ivan Procházka ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
Positron Annihilation ◽  
High Pressure Torsion ◽  
Coarse Grained ◽  
Scanning Calorimetry ◽  
Fine Grained ◽  
Β Phase ◽  
Lower Temperature

Precipitation effects in age-hardenable Mg-13wt.%Tb alloy were investigated in this work. The solution treated alloy was subjected to isochronal annealing and decomposition of the supersaturated solid solution was investigated by positron annihilation spectroscopy combined with transmission electron microscopy, electrical resistometry, differential scanning calorimetry and microhardness measurements. Peak hardening was observed at 200°C due to precipitation of finely dispersed particles of β phase with the D019structure. Vacancy-like defects associated with β phase particles were detected by positron annihilation. At higher temperatures precipitation of β and subsequently β phase takes place. Formation of these phases lead to some additional hardening and introduces open volume defects at precipitate/matrix interfaces. To elucidate the effect of plastic deformation on the precipitation sequence we studied also a Mg-13wt.%Tb alloy with ultra fine grained structure prepared by high pressure torsion. In the ultra fine grained alloy precipitation of the β phase occurs at lower temperature compared to the coarse grained material and the peak hardening is shifted to a lower temperature as well. This effect can be explained by enhanced diffusivity of Mg and Tb atoms due to a dense network of grain boundaries and high density of dislocations introduced by severe plastic deformation. Moreover, dislocations and grain boundaries serve also as nucleation sites for precipitates. Hence, precipitation effects are accelerated in the alloy subjected to severe plastic deformation.

Positron Annihilation Studies of Microstructure of Ultra Fine Grained Metals Prepared by Severe Plastic Deformation

2005 ◽  
Vol 482 ◽  
pp. 207-210 ◽  
Author(s):  
Jakub Čížek ◽  
Ivan Procházka ◽  
Bohumil Smola ◽  
Ivana Stulíková ◽  
Radomír Kužel ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Spatial Distribution ◽  
Severe Plastic Deformation ◽  
Positron Annihilation ◽  
Equal Channel Angular Pressing ◽  
High Pressure Torsion ◽  
Positron Annihilation Spectroscopy ◽  
Fine Grained ◽  
Angular Pressing

In the present work, positron annihilation spectroscopy (PAS) is employed for microstructure investigations of various ultra fine grained (UFG) metals (Cu, Ni, Fe) prepared by severe plastic deformation (SPD), namely high-pressure torsion (HPT) and equal channel angular pressing (ECAP). Generally, UFG metals prepared using both the techniques exhibit two kinds of defects introduced by SPD: dislocations and small microvoids. The size of the microvoids is determined from the PAS data. Significantly larger microvoids are found in HPT deformed Fe and Ni compared to HPT deformed Cu. The microstructure of UFG Cu prepared by HPT and ECAP is compared and the spatial distribution of defects in UFG Cu samples is characterized. In addition, the microstructure of a pure UFG Cu prepared by HPT and HPT deformed Cu+Al2O3 nanocomposite (GlidCop) is compared.

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.

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.

Recrystallization and Grain Growth in Ultra Fine Grained Materials Produced by High Pressure Torsion

2012 ◽  
Vol 715-716 ◽  
pp. 373-373
Author(s):  
Anahita Khorashadizadeh ◽  
Myrjam Winning ◽  
Stefan Zaefferer ◽  
Dierk Raabe
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
Grain Growth ◽  
High Pressure Torsion ◽  
Fine Grained ◽  
Fine Grained Material

Investigations of the microstructure of materials processed via severe plastic deformation methods such as high pressure torsion (HPT) and their recrystallization behaviour is of great interest as they are capable of producing ultra fine grained material (UFD) with good mechanical properties.

scholarly journals Dynamic High Pressure Torsion (DHPT)—A Novel Method for High Strain Rate Severe Plastic Deformation

Proceedings ◽  
2018 ◽  
Vol 2 (8) ◽  
pp. 493 ◽  
Author(s):  
Harishchandra Lanjewar ◽  
Leo Kestens ◽  
Patricia Verleysen
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
High Pressure Torsion ◽  
Pure Aluminum ◽  
High Deformation ◽  
Fine Grained

Metals with a fine-grained microstructure have exceptional mechanical properties. Severe plastic deformation (SPD) is one of the most successful ways to fabricate ultrafine-grained (UFG) and nanostructured (NC) materials. Most of the SPD techniques employ very low processing speeds. However, the lowest steady-state grain size which can be obtained by SPD is considered to be inversely proportional with the strain rate at which the severe deformation is imposed. In order to overcome this limitation, methods operating at higher rates have been envisaged and used to study the fragmentation process and the properties of the obtained materials. However, almost none of these methods, employ hydrostatic pressures which are needed to prevent the material from failing at high deformation strains. As such, their applicability is limited to materials with a high intrinsic ductility. Additionally, in some methods the microstructural changes are limited to the surface layers of the material. To circumvent these restrictions, a novel facility has been designed and developed which deforms the material at high strain rate under high hydrostatic pressures. Using the facility, commercially pure aluminum was processed and analysis of the deformed material was performed. The microstructure evolution in this material was compared with that observed in static high pressure torsion (HPT) processed material.

The State of Grain Boundaries and Grain-Boundary Diffusion in Ultrafine-Grained Mo Obtained by Severe Plastic Deformation

2016 ◽  
Vol 367 ◽  
pp. 130-139 ◽  
Author(s):  
Vladimir V. Popov ◽  
A.V. Sergeev
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Grain Boundary ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
High Pressure Torsion ◽  
Grain Boundary Diffusion ◽  
Fast Diffusion ◽  
Non Equilibrium

The grain-boundary diffusion of Co in ultra-fine grained Mo processed by high-pressure torsion has been studied by emission Mössbauer spectroscopy and radio-tracer analysis. It is demonstrated that under the severe plastic deformation by high-pressure torsion the non-equilibrium grain boundaries are formed which are the ultra-fast diffusion paths. At annealing in the temperature range of 623-823 K the relaxation of the non-equilibrium boundaries proceeds and their properties approach to those of equilibrium boundaries of recrystallization origin.

scholarly journals Improved Tensile Ductility by Severe Plastic Deformation for Nano-Structured Metallic Glass

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1611 ◽  
Author(s):  
Yue Dong ◽  
Suya Liu ◽  
Johannes Biskupek ◽  
Qingping Cao ◽  
Xiaodong Wang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Plastic Strain ◽  
Severe Plastic Deformation ◽  
Volume Fraction ◽  
High Pressure Torsion ◽  
Homogeneous Material ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Strain Limit ◽  
Small Volume Fraction

The effect of severe plastic deformation by high-pressure torsion (HPT) on the structure and plastic tensile properties of two Zr-based bulk metallic glasses, Zr55.7Ni10Al7Cu19Co8.3 and Zr64Ni10Al7Cu19, was investigated. The compositions were chosen because, in TEM investigation, Zr55.7Ni10Al7Cu19Co8.3 exhibited nanoscale inhomogeneity, while Zr64Ni10Al7Cu19 appeared homogeneous on that length scale. The nanoscale inhomogeneity was expected to result in an increased plastic strain limit, as compared to the homogeneous material, which may be further increased by severe mechanical work. The as-cast materials exhibited 0.1% tensile plasticity for Zr64Ni10Al7Cu19 and Zr55.7Ni10Al7Cu19Co8.3. Following two rotations of HPT treatment, the tensile plastic strain was increased to 0.5% and 0.9%, respectively. Further testing was performed by X-ray diffraction and by differential scanning calorimetry. Following two rotations of HPT treatment, the initially fully amorphous Zr55.7Ni10Al7Cu19Co8.3 exhibited significantly increased free volume and a small volume fraction of nanocrystallites. A further increase in HPT rotation number did not result in an increase in plastic ductility of both alloys. Possible reasons for the different mechanical behavior of nanoscale heterogeneous Zr55.7Ni10Al7Cu19Co8.3 and homogeneous Zr64Ni10Al7Cu19 are presented.

The Enhanced Kinetics of Precipitation Effects in Ultra Fine Grained Mg Alloys Prepared by High Pressure Torsion

2008 ◽  
Vol 273-276 ◽  
pp. 75-80 ◽  
Author(s):  
Jakub Čížek ◽  
Ivan Procházka ◽  
Bohumil Smola ◽  
Ivana Stulíková ◽  
Vladivoj Očenášek ◽  
...  
Keyword(s):  
High Pressure ◽  
Grain Boundaries ◽  
Volume Fraction ◽  
High Pressure Torsion ◽  
Mg Alloys ◽  
Coarse Grained ◽  
Fine Grained ◽  
Transmission Electron ◽  
Positron Lifetime Spectroscopy ◽  
Kinetics Of

Precipitation effects in ultra fine grained (UFG) lightweight Mg-based alloys were studied in the present work by means of positron lifetime spectroscopy, transmission electron microscopy, and microhardness. The UFG samples with grain size around 100 nm were fabricated by high pressure torsion (HPT). The UFG structure contains a significant volume fraction of grain boundaries and exhibits a high number of lattice defects (mainly dislocations) introduced by severe plastic deformation during the HPT processing. A high dislocation density and volume fraction of grain boundaries enhance the long range diffusion of solute elements. Moreover, dislocations and grain boundaries act as nucleation centers for precipitates. As a consequence, the precipitation effects are facilitated in the UFG alloys compared to the conventional coarse-grained samples. This phenomenon was examined in this work by comparison of the precipitation sequence in Mg alloys with UFG structure and solution treated coarse-grained alloys.

scholarly journals Ultra Fine-Grained Metals Prepared by Severe Plastic Deformation: A Positron Annihilation Study

2005 ◽  
Vol 107 (5) ◽  
pp. 745-752 ◽  
Author(s):  
J. Čížek ◽  
I. Procházka ◽  
R. Kužel ◽  
Z. Matĕj ◽  
V. Cherkaska ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Positron Annihilation ◽  
Fine Grained ◽  
Positron Annihilation Study

scholarly journals The Effect of Predeformation on Creep Strength of 9% Cr Steel

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5330
Author(s):  
Petr Král ◽  
Jiří Dvořák ◽  
Wolfgang Blum ◽  
Václav Sklenička ◽  
Zenji Horita ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
High Pressure Torsion ◽  
Tensile Creep ◽  
Initial Stresses ◽  
High Angle ◽  
Creep Tests ◽  
P92 Steel

Martensitic creep-resistant P92 steel was deformed by different methods of severe plastic deformation such as rotation swaging, high-pressure sliding, and high-pressure torsion at room temperature. These methods imposed significantly different equivalent plastic strains of about 1–30. It was found that rotation swaging led to formation of heterogeneous microstructures with elongated grains where low-angle grain boundaries predominated. Other methods led to formation of ultrafine-grained (UFG) microstructures with high frequency of high-angle grain boundaries. Constant load tensile creep tests at 873 K and initial stresses in the range of 50 to 300 MPa revealed that the specimens processed by rotation swaging exhibited one order of magnitude lower minimum creep rate compared to standard P92 steel. By contrast, UFG P92 steel is significantly softer than standard P92 steel, but differences in their strengths decrease with increasing stress. Microstructural results suggest that creep behavior of P92 steel processed by severe plastic deformation is influenced by the frequency of high-angle grain boundaries and grain coarsening during creep.

Sign in / Sign up

Export Citation Format

Share Document