Recrystallization and Grain Growth due to Annealing of an Ultrafine-Grained Al Alloy

2013 ◽  
Vol 753 ◽  
pp. 303-306
Author(s):  
Aicha Loucif ◽  
Roberto B. Figueiredo ◽  
Thierry Baudin ◽  
François Brisset ◽  
Terence G. Langdon
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Vickers Microhardness ◽  
High Pressure Torsion ◽  
Al Alloy ◽  
Size Refinement ◽  
Ultrafine Grained ◽  
Different Temperatures ◽  
Deformed State ◽  
Misorientation Angles

The evolution of the recrystallization microstructure at different temperatures and the related change in the microhardness were studied in an Al-6061 alloy after 2 turns of high-pressure torsion (HPT) by means of Vickers microhardness and EBSD analysis. The corresponding results show that HPT processing introduces a significant grain size refinement for the deformed state by comparison with the 150 µm grain size in the initial material. The microstructure after annealing at 200°C is relatively close to the as-processed one and the distribution of misorientation angles remains essentially unchanged. However, significant microstructural changes are produced with increasing annealing temperature and at the highest temperature (400°C) there is an abnormal grain growth. The variation of Vickers microhardness (Hv) after the different annealing treatments show a gradual decrease when the temperature increases.

scholarly journals Effect of Grain Boundaries on the Electron Work Function of Ultrafine Grained Aluminum

2018 ◽  
Vol 57 (1) ◽  
pp. 110-115 ◽  
Author(s):  
T.S. Orlova ◽  
A.V. Ankudinov ◽  
A.M. Mavlyutov ◽  
N.N. Resnina
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Work Function ◽  
High Pressure Torsion ◽  
Electron Work Function ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Different Temperatures ◽  
First Time ◽  
Specific Length

Abstract The electron work function (EWF) of ultrafine grained (UFG) aluminum structured by high pressure torsion (HPT) has been investigated. For the first time, the dependence of the EWF on the specific length of grain boundaries (or the grain size) for UFG Al has been obtained. The change of average grain size was achieved by short term annealing of HPT-processed aluminum at different temperatures from the range 90-400 °C. It has been shown that the state of grain boundaries (GBs) affects the magnitude of the EWF. It has been found that the transformation of GBs due to annealing at 90 °C from a nonequilibrium to more equilibrium state while maintaining the specific length of GBs and their average misorientation is accompanied by a decrease in average GB specific energy by 0.3 J m-2. This transition provides a sharp increase in the EWF of the UFGAl by 0.25 eV.

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.

Functional Properties of Ti-Ni-Based Shape Memory Alloys

2008 ◽  
Vol 59 ◽  
pp. 156-161 ◽  
Author(s):  
I. Khmelevskaya ◽  
Sergey Prokoshkin ◽  
Vladimir Brailovski ◽  
K.E. Inaekyan ◽  
Vincent Demers ◽  
...  
Keyword(s):  
Grain Size ◽  
Cold Rolling ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Functional Properties ◽  
High Pressure Torsion ◽  
Martensitic Transformations ◽  
Critical Temperatures ◽  
Recoverable Strain ◽  
Ultrafine Grained

The main functional properties (FP) of Ti-Ni Shape Memory Alloys (SMA) are their critical temperatures of martensitic transformations, their maximum completely recoverable strain (er,1 max) and maximum recovery stress (sr max). Control of the Ti-Ni-based SMA FP develops by forming well-developed dislocation substructures or ultrafine-grained structures using various modes of thermomechanical treatment (TMT), including severe plastic deformation (SPD). The present work shows that TMT, including SPD, under conditions of high pressure torsion (HPT), equal-channel angular pressing (ECAP) or severe cold rolling followed by post-deformation annealing (PDA), which creates nanocrystalline or submicrocrystalline structures, is more beneficial from SMA FP point of view than does traditional TMT creating well-developed dislocation substructure. ECAP and low-temperature TMT by cold rolling followed by PDA allows formation of submicrocrystalline or nanocrystalline structures with grain size from 20 to 300 nm in bulk, and long-size samples of Ti-50.0; 50.6; 50.7%Ni and Ti-47%Ni-3%Fe alloys. The best combination of FP: sr max =1400 MPa and er,1 max=8%, is reached in Ti-Ni SMA after LTMT with e=1.9 followed by annealing at 400°C which results in nanocrystalline (grain size of 50 to 80 nm) structure formation. Application of ultrafine-grained SMA results in decrease in metal consumption for various medical implants and devices based on shape memory and superelastiсity effects.

Enhanced Densification and Grain-Size Refinement in Cation-Doped Tetragonal Zirconia

2010 ◽  
Vol 62 ◽  
pp. 227-231
Author(s):  
Keijiro Hiraga ◽  
Hidehiro Yoshida ◽  
Koji Morita ◽  
Byung Nam Kim
Keyword(s):  
Grain Size ◽  
Relative Density ◽  
Grain Growth ◽  
Sintering Temperature ◽  
Initial Density ◽  
Tetragonal Zirconia ◽  
The Other ◽  
Size Refinement ◽  
Grain Sizes ◽  
Materials Used

In tetragonal zirconia, possibility is investigated of densification with finer grain sizes under the combination of doping and sintering in air. The materials used are CIP'ed compacts of 3-mol%-yttria-stabilized tetragonal zirconia (3Y-TZP) doped with a small amount of cations. For a given sintering temperature and initial density of the compacts, while the doped cations enhances densification in the latest stage of sintering, the effect is different in grain growth during densification: a doped cation tended to enhance grain growth, whereas the other cations tended to suppress grain growth. As a result, the doping of the latter cations brings about a grain size finer than that of the undoped 3Y-TZP for a given relative density.

Submicrocrystalline Austenitic Stainless Steel Processed by Cold or Warm High Pressure Torsion

2016 ◽  
Vol 838-839 ◽  
pp. 398-403 ◽  
Author(s):  
Marina Tikhonova ◽  
Nariman Enikeev ◽  
Ruslan Z. Valiev ◽  
Andrey Belyakov ◽  
Rustam Kaibyshev
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Severe Plastic Deformation ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Submicrocrystalline Structure ◽  
Ultrafine Grained ◽  
Different Temperatures

The formation of submicrocrystalline structure during severe plastic deformation and its effect on mechanical properties of an S304H austenitic stainless steel with chemical composition of Fe – 0.1C – 0.12N – 0.1Si – 0.95Mn – 18.4Cr – 7.85Ni – 3.2Cu – 0.5Nb – 0.01P – 0.006S (all in mass%) were studied. The severe plastic deformation was carried out by high pressure torsion (HPT) at two different temperatures, i.e., room temperature or 400°C. HPT at room temperature or 400°C led to the formation of a fully austenitic submicrocrystalline structure. The grain size and strength of the steels with ultrafine-grained structures produced by cold or warm HPT were almost the same. The ultimate tensile strengths were 1950 MPa and 1828 MPa after HPT at room temperature and 400°C, respectively.

scholarly journals Production of Ultrafine Grained Hardmetals by Electrical Resistance Sintering

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 159 ◽  
Author(s):  
Jesús Cintas ◽  
Raquel Astacio ◽  
Francisco Cuevas ◽  
Juan Montes ◽  
Thomas Weissgaerber ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Electrical Resistance ◽  
Processing Parameters ◽  
Medium Frequency ◽  
Main Achievement ◽  
Processing Times ◽  
Ultrafine Grained ◽  
Protective Atmospheres ◽  
Optimal Values

In this work, powders of cemented ultrafine WC-6 wt.% Co were consolidated. The feasibility of the medium frequency electrical resistance sintering (MF-ERS) technique were studied to prevent WC grain growth during consolidation. Porosity and hardness were measured at different zones of the MF-ERS compacts. The compacts showed a slight inhomogeneity in their properties across their section, but it was controlled by choosing suitable values of the processing parameters. The optimal values for the material studied were current intensities between 7 and 8 kA and sintering times between 600 and 800 ms. The main achievement using this consolidation method was that sintered compacts essentially maintained the initial WC grain size. This was attained to processing times of less than 2 s, and without the need for using protective atmospheres.

Structure and Fatigue Properties of the Mg Alloy AM60 Processed by ECAP

2008 ◽  
Vol 584-586 ◽  
pp. 803-808 ◽  
Author(s):  
Rinat K. Islamgaliev ◽  
Olya B. Kulyasova ◽  
Bernhard Mingler ◽  
Michael Zehetbauer ◽  
Alexander Minkow
Keyword(s):  
Grain Size ◽  
Endurance Limit ◽  
Volume Fraction ◽  
Coarse Grained ◽  
Fatigue Properties ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Mean Grain Size ◽  
Fatigue Endurance ◽  
Misorientation Angles

This paper reports on the microstructures and fatigue properties of ultrafine-grained (UFG) AM60 magnesium alloy processed by equal channel angular pressing (ECAP) at various temperatures. After ECAP processing, samples exhibited an increase in fatigue endurance limit, which correlates well with a decrease in grain size. In case of lowest ECAP temperature, the mean grain size is as small as 1 2m which leads to an increase in fatigue endurance limit by 70 % in comparison to coarse-grained alloy. The temperature of ECAP not only governs the grain size and misorientation angles of grain boundaries but also the volume fraction of precipitates, thus affecting the probability of twinning and grain growth after fatigue treatment.

Microstructure and Mechanical Properties of Ultrafine-Grained Mg-Zn-Ca Alloy

2017 ◽  
Vol 381 ◽  
pp. 39-43 ◽  
Author(s):  
Olya B. Kulyasova ◽  
Rinat K. Islamgaliev ◽  
Ruslan Z. Valiev
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
High Pressure ◽  
Chemical Composition ◽  
High Pressure Torsion ◽  
Notable Effect ◽  
Ultrafine Grained ◽  
Mean Grain Size ◽  
High Microhardness ◽  
Mean Size

This paper studies the structure and mechanical properties of the Mg-1%Zn-xCa system subjected to high-pressure torsion (HPT) treatment. It was found that the chemical composition had a notable effect on the processes of grain refinement in the alloy. As is shown, HPT of Mg-1%Zn-0.005%Ca resulted in the formation of grains with a mean size of 250 nm, while HPT of the alloy with an increased content of Са up to 0.2% led to the formation of a nanostructure with a mean grain size of 90 nm. It is demonstrated that high microhardness is typical of all HPT-processed samples. The formation of fine Mg2Ca particles was established to increase the heat resistance of the alloy.

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