Effect of Pressure on the Final Grain Size after High Pressure Torsion

2013 ◽  
pp. 133-140 ◽  
Author(s):  
T. Hebesberger ◽  
R. Pippan ◽  
H.P. Stüwe
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Effect Of Pressure

The Processing of Ultrafine-Grained Materials Using High-Pressure Torsion

2007 ◽  
Vol 558-559 ◽  
pp. 1283-1294 ◽  
Author(s):  
Cheng Xu ◽  
Z. Horita ◽  
Terence G. Langdon
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Metallic Materials ◽  
Grain Sizes ◽  
Ultrafine Grained ◽  
Wide Range ◽  
Ultrafine Grained Materials ◽  
Thin Disks

It is now well-established that processing through the application of severe plastic deformation (SPD) leads to a significant reduction in the grain size of a wide range of metallic materials. This paper examines the fabrication of ultrafine-grained materials using high-pressure torsion (HPT) where this process is attractive because it leads to exceptional grain refinement with grain sizes that often lie in the nanometer or submicrometer ranges. Two aspects of HPT are examined. First, processing by HPT is usually confined to samples in the form of very thin disks but recent experiments demonstrate the potential for extending HPT also to bulk samples. Second, since the strains imposed in HPT vary with the distance from the center of the disk, it is important to examine the development of inhomogeneities in disk samples processed by HPT.

Thermal Stability of Ultrafine-Grained Pure Titanium Processed by High-Pressure Torsion

2021 ◽  
Vol 1016 ◽  
pp. 338-344
Author(s):  
Wan Ji Chen ◽  
Jie Xu ◽  
De Tong Liu ◽  
De Bin Shan ◽  
Bin Guo ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Grain Size ◽  
High Pressure ◽  
Annealing Temperature ◽  
High Pressure Torsion ◽  
Stored Energy ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Thermal Stability Of

High-pressure torsion (HPT) was conducted under 6.0 GPa on commercial purity titanium up to 10 turns. An ultrafine-grained (UFG) pure Ti with an average grain size of ~96 nm was obtained. The thermal properties of these samples were studied by using differential scanning calorimeter (DSC) which allowed the quantitative determination of the evolution of stored energy, the recrystallization temperatures, the activation energy involved in the recrystallization of the material and the evolution of the recrystallized fraction with temperature. The results show that the stored energy increases, beyond which the stored energy seems to level off to a saturated value with increase of HPT up to 5 turns. An average activation energy of about 101 kJ/mol for the recrystallization of 5 turns samples was determined. Also, the thermal stability of the grains of the 5 turns samples with subsequent heat treatments were investigated by microstructural analysis and Vickers microhardness measurements. It is shown that the average grain size remains below 246 nm when the annealing temperature is below 500 °C, and the size of the grains increases significantly for samples at the annealing temperature of 600 °C.

scholarly journals Exceptional Strengthening of Biodegradable Mg-Zn-Ca Alloys through High Pressure Torsion and Subsequent Heat Treatment

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2460 ◽  
Author(s):  
Jelena Horky ◽  
Abdul Ghaffar ◽  
Katharina Werbach ◽  
Bernhard Mingler ◽  
Stefan Pogatscher ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
High Pressure ◽  
Tensile Strength ◽  
High Pressure Torsion ◽  
Type Equation ◽  
Subsequent Heat Treatment ◽  
Strength Increase ◽  
Dislocation Loops ◽  
High Concentration

In this study, two biodegradable Mg-Zn-Ca alloys with alloy content of less than 1 wt % were strengthened via high pressure torsion (HPT). A subsequent heat treatment at temperatures of around 0.45 Tm led to an additional, sometimes even larger increase in both hardness and tensile strength. A hardness of more than 110 HV and tensile strength of more than 300 MPa were achieved in Mg-0.2Zn-0.5Ca by this procedure. Microstructural analyses were conducted by scanning and transmission electron microscopy (SEM and TEM, respectively) and atom probe tomography (APT) to reveal the origin of this strength increase. They indicated a grain size in the sub-micron range, Ca-rich precipitates, and segregation of the alloying elements at the grain boundaries after HPT-processing. While the grain size and segregation remained mostly unchanged during the heat treatment, the size and density of the precipitates increased slightly. However, estimates with an Orowan-type equation showed that precipitation hardening cannot account for the strength increase observed. Instead, the high concentration of vacancies after HPT-processing is thought to lead to the formation of vacancy agglomerates and dislocation loops in the basal plane, where they represent particularly strong obstacles to dislocation movement, thus, accounting for the considerable strength increase observed. This idea is substantiated by theoretical considerations and quenching experiments, which also show an increase in hardness when the same heat treatment is applied.

scholarly journals Grain size and microhardness evolution during annealing of a magnesium alloy processed by high-pressure torsion

2015 ◽  
Vol 4 (1) ◽  
pp. 14-17 ◽  
Author(s):  
Livia Raquel C. Malheiros ◽  
Roberto Braga Figueiredo ◽  
Terence G. Langdon
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Magnesium Alloy ◽  
High Pressure Torsion

An Investigation of Microtexture Evolution in an AlMgSi Alloy Processed by High-Pressure Torsion

2011 ◽  
Vol 702-703 ◽  
pp. 165-168 ◽  
Author(s):  
Aicha Loucif ◽  
Thierry Baudin ◽  
François Brisset ◽  
Roberto B. Figueiredo ◽  
Rafik Chemam ◽  
...  
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Distribution Function ◽  
High Pressure Torsion ◽  
Electron Backscatter Diffraction ◽  
Orientation Distribution ◽  
Homogeneous Microstructure ◽  
Electron Backscatter ◽  
Backscatter Diffraction ◽  
Almgsi Alloy

This investigation uses electron backscatter diffraction (EBSD) to study the development of microtexture with increasing deformation in an AlMgSi alloy having an initial grain size of about 150 µm subjected to high pressure torsion (HPT) up to a total of 5 turns. An homogeneous microstructure was achieved throughout the disc sample at high strains with the formation of ultra-fine grains. Observations based on orientation distribution function (ODF) calculation reveals the presence of the torsion texture components often reported in the literature for f.c.c. materials. In particular, the C {001}<110> component was found to be dominant. Furthermore, no significant change in the texture sharpness was observed by increasing the strain.

scholarly journals DIFFUSIVE AND DISPLACIVE PHASE TRANSFORMATIONS UNDER HIGH PRESSURE TORSION

2019 ◽  
Vol 25 (4) ◽  
pp. 230 ◽  
Author(s):  
Boris Straumal ◽  
Askar Kilmametov ◽  
Andrey Mazilkin ◽  
Olga Kogtenkova ◽  
Brigitte Baretzky ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Plastic Deformation ◽  
Grain Size ◽  
High Pressure ◽  
Phase Composition ◽  
Steady State ◽  
Phase Transformations ◽  
High Pressure Torsion ◽  
Dynamic Equilibrium ◽  
Initial State

<p class="AMSmaintext"><span lang="EN-GB">Severe plastic deformation (SPD) can induce various phase transformations. After a certain strain, the dynamic equilibrium establishes between defects production by an external force and their relaxation (annihilation). The grain size, hardness, phase composition etc. in this steady-state does not depend on the initial state of a material and is, therefore, equifinal. In this review we discuss the competition between precipitation and dissolution of precipitates, amorphization and (nano)crystallization, SPD-induced accelerated mass-transfer, allotropic and martensitic transitions and formation of grain boundary phases.</span></p>

Microstructural Evolution in an Al-6061 Alloy Processed by High-Pressure Torsion and Rapid Annealing

2010 ◽  
Vol 667-669 ◽  
pp. 223-228 ◽  
Author(s):  
Aicha Loucif ◽  
Roberto B. Figueiredo ◽  
Thierry Baudin ◽  
François Brisset ◽  
Terence G. Langdon
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Grain Refinement ◽  
High Pressure Torsion ◽  
Applied Pressure ◽  
Al 6061 ◽  
Fine Grain ◽  
Grain Structures ◽  
Average Grain Size ◽  
Continuous Recrystallization

The processing of bulk metals through the application of severe plastic deformation provides the opportunity for introducing significant grain refinement into bulk solids. In the present investigation, an aluminum alloy (Al-6061) was processed by high-pressure torsion (HPT) at room temperature under an applied pressure of 6.0 GPa up to a total of 5 turns. Detailed measurements after processing revealed the occurrence of continuous grain refinement and material strengthening with increasing imposed strain. The average grain size of the alloy was reduced from ~150 m to a grain size in the range of ~500 nm through processing by HPT. Although there was a difference in the average grain size of samples processed to different levels of imposed strain, careful inspection showed that the structures became similar after annealing at 250°C for 5 min. This suggests that the additional grain refinement introduced at large amounts of deformations is less stable at high temperatures. The results of this investigation, including the distributions of the grain sizes after annealing, are consistent with the predictions of a model based on the occurrence of continuous recrystallization in aluminum alloys having fine grain structures, large fractions of high-angle grain boundaries and where there is a large amount of deformation.

Thermo- and Deformation Induced Martensitic Transformations in Binary TiNi-Based Alloys Subjected to Severe Plastic Deformation

2013 ◽  
Vol 738-739 ◽  
pp. 530-534 ◽  
Author(s):  
Natalia N. Kuranova ◽  
Vladimir V. Makarov ◽  
Vladimir G. Pushin ◽  
Alexey N. Uksusnikov
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
High Pressure Torsion ◽  
Amorphous State ◽  
Cold Drawing ◽  
Martensitic Transformations ◽  
Subsequent Annealing ◽  
Structure And Phase Transformations

Results of investigations of structure and phase transformations and properties of the TiNi-based alloys with a shape memory effect (SME) after severe plastic deformation (SPD) by cold rolling, cold drawing, high pressure torsion and subsequent annealing are reported. It is found that the baroelastic effects related to the highly reversible martensitic transformations can occur in alloys, subjected to high pressure. The evolution of fine structure of the alloys into nanocrystalline and then amorphous state during SPD and after subsequent annealing have been studied. The effect of grain size on the martensitic transformations and properties of the alloys is discussed.

Microstructure and Thermal Stability of Copper - Carbon Nanotube Composites Consolidated by High Pressure Torsion

2012 ◽  
Vol 729 ◽  
pp. 228-233 ◽  
Author(s):  
P. Jenei ◽  
E.Y. Yoon ◽  
Jenő Gubicza ◽  
Hyoung Seop Kim ◽  
J.L. Lábár ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Grain Size ◽  
High Pressure ◽  
Dislocation Density ◽  
High Pressure Torsion ◽  
Lattice Defect ◽  
Taylor Formula ◽  
Processing Temperature ◽  
Pure Cu ◽  
Thermal Stability Of

Blends of Cu powders and 3 vol. % carbon nanotubes (CNTs), and an additional sample from pure Cu powder were consolidated by High Pressure Torsion (HPT) at room temperature (RT) and 373 K. The grain size, the lattice defect densities as well as the hardness of the pure and composite materials were determined. Due to the pinning effect of CNTs, the dislocation density is about three times larger, while the grain size is about half of that obtained in the sample consolidated from the pure Cu powder. The increase of the HPT-processing temperature from RT to 373 K resulted in only a slight increase of the grain size in the Cu-CNT composite while the dislocation density and the twin boundary frequency were reduced significantly. The flow stress obtained experimentally agrees well with the value calculated by the Taylor-formula indicating that the strength in both pure Cu and Cu-CNT composites is determined mainly by the interaction between dislocations. The addition of CNTs to Cu yields a significantly better thermal stability of the UFG matrix processed by HPT.

Comparison between FEM and Experimental Results in the Upsetting of Nano-Structured Materials

2012 ◽  
Vol 713 ◽  
pp. 31-36 ◽  
Author(s):  
C.J. Luis-Pérez ◽  
Ignacio Puertas ◽  
Daniel Salcedo ◽  
Javier León ◽  
Ivan Pérez
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Pressure ◽  
Severe Plastic Deformation ◽  
Equal Channel Angular Extrusion ◽  
High Pressure Torsion ◽  
Experimental Results ◽  
Structured Materials ◽  
Angular Extrusion ◽  
Deformation Processes

Over recent years, some severe plastic deformation processes have been developed with the aim of obtaining a material with sub-micrometric or even nanometric grain size, such as: ECAE (Equal channel angular extrusion) and HPT (High pressure torsion) among many others. The main aim of this present study is to analyse the upsetting of the 5083 Al-Mg-Mn alloy, which had been previously deformed by ECAE. Different processing temperatures will be used and the final properties of the resulting material will be determined.

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