REGULARITIES OF FORMATION AND DEGRADATION OF THE MICROSTRUCTURE AND PROPERTIES OF NEW ULTRAFINE-GRAINED LOW-MODULUS Ti–Nb–Mo–Zr ALLOYS

2018 ◽  
pp. 36-48
Author(s):  
Yu. R. Kolobov ◽  
O. A. Golosova ◽  
S. S. Manokhin
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Pressure Torsion ◽  
Diffraction Method ◽  
Simultaneous Action ◽  
Helical Rolling ◽  
Longitudinal Rolling ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Low Modulus

Regularities of the formation of ultrafine-grained (UFG) and submicrocrystalline (SMC) structures in new nickel-free low-modulus Ti–Nb–Mo–Zr titanium β alloys under the action of plastic deformation were studied. Temperature-time ranges of the development of dynamic recrystallization processes under the simultaneous action of temperature and plastic deformation were determined. The recrystallization diagram of II type of the Ti–28Nb–8Mo–12Zr alloy was constructed and analyzed. It was shown using scanning electron microscopy and electron backscatter diffraction method that the UFG structure with an average grain size of no more than 7 μm and high fraction of high-angle grain boundaries is formed in the investigated alloys as a result of longitudinal rolling followed by annealing for quenching. It was found that the formation of the UFG structure leads to a significant increase in the strength and plastic characteristics of these alloys. The regularities of the formation of UFG and SMC structures in the titanium β alloys Ti–28Nb–8Mo–12Zr and VT30 widely used in industry under the action of plastic deformation by the helical rolling method were studied. It was shown that the helical rolling of the VT30 alloy leads to the formation of the homogeneous UFG state as opposite to the developed Ti–28Nb–8Mo–12Zr β alloy where this method causes structure softening with micropores and microcracks formed in the central region. It is possible to form a nanostructured state with an average grain size of about 100 nm in Ti–Nb–Mo–Zr titanium β alloys using high-pressure torsion method.

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 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.

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).

Measurement of WC Grain Size in Ultrafine Grained WC-Co Cemented Carbides

2013 ◽  
Vol 278-280 ◽  
pp. 460-463 ◽  
Author(s):  
Yi Gao Yuan ◽  
Xiao Xiao Zhang ◽  
Jian Jun Ding ◽  
Jun Ruan
Keyword(s):  
Grain Size ◽  
Diffraction Method ◽  
Cemented Carbides ◽  
Polished Surface ◽  
Grain Sizes ◽  
Ultrafine Grained ◽  
Average Grain Size ◽  
Measurement Results ◽  
Backscattered Electron ◽  
Imagej Software

Based on the backscattered electron (BSE) images and IMAGEJ image analysis software, the average grain size of WC in ultrafine grained WC-Co cemented carbides was measured. The result shows that BSE images of the polished surface not be etched are suitable for quantitative evaluating the grain size of WC in the ultrafine grained hardmetals. Both linear intercept method and equivalent circle diameter method can be used to accurately measure the grain sizes of WC in ultrafine grained hadmetals by using IMAGEJ software. Measurement results of WC grain sizes coincide with the conclusion of X-ray diffraction method

Equal Channel Angular Pressing in a Pearlitic Structured Steel

2007 ◽  
Vol 539-543 ◽  
pp. 4692-4697
Author(s):  
Jun Xia Huang ◽  
Jing Tao Wang
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Shear Deformation ◽  
Equal Channel Angular Pressing ◽  
Ferrite Matrix ◽  
Nucleation And Growth ◽  
Additional Energy ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Average Grain Size

Equal Channel Angular Pressing (ECAP) in a fully pearlitic structured steel 65Mn was successfully carried out at 923 K via route C in this study. The severe shear deformation of ECAP was accommodated by periodical bending, periodical shearing and shearing fracture etc in the pearlitic lamellae. The cementite in the pearlite has higher plastic deformation capability. Excessive imperfections may be introduced into the cementite, which supplies additional energy driving for the following spheroidization of cementite in subsequent processing. After five ECAP passes, the fully pearlitic lamellae evolved into a microstructure of ultrafine-grained ferrite matrix uniformly dispersed with finer cementite particles. The ferrite matrix is homogeneous with an average grain size of ~0.3 micrometers. Two possible mechanism for the spheroidization of cementite were proposed：heterogeneous growth of the fractured cementite fragments, and the precipitation of new fine spherical cementite particles through nucleation and growth.

Ultrafine Grained Low Carbon Steels Processed by Severe Plastic Deformation

2008 ◽  
Vol 584-586 ◽  
pp. 623-630 ◽  
Author(s):  
Sergey V. Dobatkin ◽  
P.D. Odessky ◽  
Svetlana V. Shagalina
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
High Pressure Torsion ◽  
High Strength ◽  
Carbon Steels ◽  
Low Alloy Steels ◽  
Low Carbon ◽  
Low Carbon Steels ◽  
Ultrafine Grained

The structure, mechanical and functional properties of ultrafine-grained low-carbon steels have been studied after severe plastic deformation (SPD) by high pressure torsion (HPT) and equalchannel angular pressing (ECAP). It is revealed that HPT of low carbon steels at a temperature below 0.3 Tm leads to the formation of nanocrystalline structure with a grain size of <100 nm or a mixture of oriented substructure and nanograins. ECAP under similar conditions leads to the formation of submicrocrystalline structure with a grain size of 200-300 nm. The initial martensitic state compared with the initial ferritic-pearlitic state of the low-carbon steels results in formation of finer structure after SPD and less intense grain growth upon heating, i.e., results in a higher thermal stability. Low-carbon low-alloy steels after ECAP are characterized by high strength (UTS > 1000 MPa) and plasticity (EL = 10-15%). The high-strength state after ECAP is retained upon tensile test testing up to a temperature of 500°C. The submicrocrystalline low-carbon steels after ECAP processing and subsequent heating is characterized by an increased impact toughness at test temperatures down to -40°C.

scholarly journals Structural Transformations and Mechanical Properties of Metastable Austenitic Steel under High Temperature Thermomechanical Treatment

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 645
Author(s):  
Igor Litovchenko ◽  
Sergey Akkuzin ◽  
Nadezhda Polekhina ◽  
Kseniya Almaeva ◽  
Evgeny Moskvichev
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Temperature ◽  
Austenitic Steel ◽  
Structural Transformations ◽  
Initial State ◽  
Twin Boundaries ◽  
Metastable Austenitic Steel ◽  
Average Grain Size ◽  
Heating Up

The effect of high-temperature thermomechanical treatment on the structural transformations and mechanical properties of metastable austenitic steel of the AISI 321 type is investigated. The features of the grain and defect microstructure of steel were studied by scanning electron microscopy with electron back-scatter diffraction (SEM EBSD) and transmission electron microscopy (TEM). It is shown that in the initial state after solution treatment the average grain size is 18 μm. A high (≈50%) fraction of twin boundaries (annealing twins) was found. In the course of hot (with heating up to 1100 °C) plastic deformation by rolling to moderate strain (e = 1.6, where e is true strain) the grain structure undergoes fragmentation, which gives rise to grain refining (the average grain size is 8 μm). Partial recovery and recrystallization also occur. The fraction of low-angle misorientation boundaries increases up to ≈46%, and that of twin boundaries decreases to ≈25%, compared to the initial state. The yield strength after this treatment reaches up to 477 MPa with elongation-to-failure of 26%. The combination of plastic deformation with heating up to 1100 °C (e = 0.8) and subsequent deformation with heating up to 600 °C (e = 0.7) reduces the average grain size to 1.4 μm and forms submicrocrystalline fragments. The fraction of low-angle misorientation boundaries is ≈60%, and that of twin boundaries is ≈3%. The structural states formed after this treatment provide an increase in the strength properties of steel (yield strength reaches up to 677 MPa) with ductility values of 12%. The mechanisms of plastic deformation and strengthening of metastable austenitic steel under the above high-temperature thermomechanical treatments are discussed.

GRAIN REFINEMENT AND MICROSTRUCTURE EVOLUTION IN ALUMINUM A2618 ALLOY BY HIGH-PRESSURE TORSION

2016 ◽  
Vol 78 (6-9) ◽  
Author(s):  
Intan Fadhlina Mohamed ◽  
Seungwon Lee ◽  
Kaveh Edalati ◽  
Zenji Horita ◽  
Shahrum Abdullah ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Grain Refinement ◽  
Room Temperature ◽  
Rotation Speed ◽  
High Pressure Torsion ◽  
Applied Pressure ◽  
Saturation Level ◽  
Microstructural Refinement ◽  
Average Grain Size

This work presents a study related to the grain refinement of an aluminum A2618 alloy achieved by High-Pressure Torsion (HPT) known as a process of Severe Plastic Deformation (SPD). The HPT is conducted on disks of the alloy under an applied pressure of 6 GPa for 1 and 5 turns with a rotation speed of 1 rpm at room temperature. The HPT processing leads to microstructural refinement with an average grain size of ~250 nm at a saturation level after 5 turns. Gradual increases in hardness are observed from the beginning of straining up to a saturation level. This study thus suggests that hardening due to grain refinement is attained by the HPT processing of the A2618 alloy at room temperature.

Investigations on Microstructure Evolution and Deformation Behavior of Aged and Ultrafine Grained Al-Zn-Mg Alloy Subjected to Severe Plastic Deformation

2010 ◽  
Vol 667-669 ◽  
pp. 253-258
Author(s):  
Wei Ping Hu ◽  
Si Yuan Zhang ◽  
Xiao Yu He ◽  
Zhen Yang Liu ◽  
Rolf Berghammer ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
Microstructure Evolution ◽  
Deformation Behavior ◽  
Deformation Mechanisms ◽  
Mg Alloy ◽  
Ultrafine Grained

An aged Al-5Zn-1.6Mg alloy with fine η' precipitates was grain refined to ~100 nm grain size by severe plastic deformation (SPD). Microstructure evolution during SPD and mechanical behaviour after SPD of the alloy were characterized by electron microscopy and tensile, compression as well as nanoindentation tests. The influence of η' precipitates on microstructure and mechanical properties of ultrafine grained Al-Zn-Mg alloy is discussed with respect to their effect on dislocation configurations and deformation mechanisms during processing of the alloy.

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