scholarly journals Microstructure and Aging Behavior of Cu-Be Alloy Processed by High-Pressure Torsion

2014 ◽  
Vol 783-786 ◽  
pp. 2707-2712 ◽  
Author(s):  
Chihiro Watanabe ◽  
Ryoichi Monzen ◽  
Seiichiro Ii ◽  
Koichi Tsuchiya
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Applied Pressure ◽  
Solution Treatment ◽  
Equivalent Strain ◽  
Aging Behavior ◽  
Fine Grained ◽  
Transmission Electron ◽  
Fine Grained Structure

The microstructure and aging behavior of Cu-1.8wt%Be-0.2wt%Co alloy specimens processed by high-pressure torsion (HPT) at room temperature (RT) and 150°C after solution treatment have been studied. Application of HPT processing at RT and 150°C under an applied pressure of 5 GPa for 10 revolutions at 1 rpm to alloy specimens (RT-and 150°C-specimen) produces an ultra-fine grained structure with a grain size of 70 nm. The hardnesses of the RT-and 150°C-specimens increase with equivalent strain up to 7 and then saturate at constant values of 400 and 430 Hv, respectively. Annealing the RT-specimen at 150°C for 10 min increases the hardness from 400 to 430 Hv. Transmission electron microscopy observations of the 150°C-specimen and the RT-specimen annealed at 150°C reveal that there are no intragranular and intergranular precipitates. It is suggested that the higher hardness of the 150°C-specimen than the RT-specimen is ascribed to the segregation of Be atoms on dislocations during HPT processing at 150°C. The RT-and 150°C-specimens harden rapidly and exhibit maximum values of hardness at 3 min during aging at 320°C. The increase in the hardness is attributed to the precipitation of finely dispersed G.P. zones.

Superplasticity of Ultra-Fine Grained 7075 Alloy Processed by High-Pressure Torsion

2014 ◽  
Vol 794-796 ◽  
pp. 807-810 ◽  
Author(s):  
Seungwon Lee ◽  
Zen Ji Horita
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Applied Pressure ◽  
Tensile Tests ◽  
Initial Strain ◽  
Strain Rates ◽  
Fine Grained ◽  
Al 7075 ◽  
7075 Alloy

An Al 7075 alloy (5.63mass%Zn-2.56mass%Mg-1.68mass%Cu-0.21mass%Fe-0.19mass%Cr-0.14mass%Si-0.02mass%Ti with balance of Al) was processed by high-pressure torsion (HPT) under an applied pressure of 6 GPa for 1, 3 and 5 revolutions with a rotation speed of 1 rpm at room temperature. Vickers microhardness saturated to a level of 220 Hv after the HPT processing and the grain size was refined to 120 nm at the state of the hardness saturation. Tensile tests were conducted with initial strain rates from 2.0 × 10-4 to 2.0 × 10-2 s-1 at temperatures as 200 °C and 250 °C (equivalent to 0.52Tm and 0.57Tm, respectively, where Tm is the melting point of the alloy). The HPT-processed samples for 3 revolutions exhibited superplastic elongations of 640% and 510% at 250 °C with initial strain rates of 2.0 × 10-3 s-1 and 2.0 × 10-2 s-1, respectively.

scholarly journals Use of Ring Sample for High-Pressure Torsion and Microstructural Evolution with Equivalent Strain

2008 ◽  
Vol 584-586 ◽  
pp. 191-196 ◽  
Author(s):  
Yuki Ito ◽  
Yosuke Harai ◽  
Tadayoshi Fujioka ◽  
Kaveh Edalati ◽  
Z. Horita
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Equivalent Strain ◽  
Ring Sample ◽  
Transmission Electron ◽  
Low Dislocation Density ◽  
Data Points ◽  
Pure Cu ◽  
Hardness Values

This study introduces a process of high-pressure torsion (HPT) using ring samples and compares with the results of conventional disk HPT. Both types of HPT were conducted at room temperature on pure Al and pure Cu. The microhardness was measured along the diameters of the disks and rings. Microstructures were examined using transmission electron microscopy. When hardness values were plotted against equivalent strain, all data points fell on a single line for each material. There was a hardness maximum for pure Al but no such a maximum was present in pure Cu. In pure Al, many dislocations were visible within grains up to the equivalent strain corresponding to the hardness maximum but beyond this strain, grains with low dislocation density appear. All materials exhibited steady state where the hardness remains constant with respect to imposed equivalent strain. This study concludes that use of ring samples is effective as an alternative to the disk samples.

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.

Microstructure Development and Precipitation Effects in Ultra Fine Grained Mg-3Tb-2Nd Alloy Prepared by High Pressure Torsion

2008 ◽  
Vol 584-586 ◽  
pp. 591-596 ◽  
Author(s):  
Jakub Čížek ◽  
Ivan Procházka ◽  
Bohumil Smola ◽  
Ivana Stulíková ◽  
Martin Vlach ◽  
...  
Keyword(s):  
High Pressure ◽  
Positron Lifetime ◽  
High Pressure Torsion ◽  
Creep Properties ◽  
Fine Grained ◽  
Transmission Electron ◽  
Highly Sensitive ◽  
Ideal Tool ◽  
Increasing Temperature

Mg-Tb-Nd ternary alloy represents a novel hardenable Mg-based alloy with enhanced strength and favorable creep properties. In the present work we studied microstructure of ultra fine grained (UFG) Mg-Tb-Nd alloy prepared by high pressure torsion (HPT). Lattice defects introduced into the specimen by the severe plastic deformation play a key role in physical properties of UFG specimens. It is known that positron lifetime (PL) spectroscopy is highly sensitive to open volume defects (like vacancies, dislocations, etc.). Therefore, PL spectroscopy is an ideal tool for defect characterizations in the HPT deformed specimens. In the present work we combined PL studies with transmission electron microscopy and microhardness measurements. After detailed characterization of the as-deformed structure, the specimens were step-by-step isochronally annealed and we investigated the development of microstructure with increasing temperature.

Microstructure and Defect Structure Evolution in Ultra-Fine Grained MgAlZn Alloy

2014 ◽  
Vol 783-786 ◽  
pp. 390-395
Author(s):  
Miloš Janeček ◽  
Jitka Stráská ◽  
Jakub Čížek ◽  
Hyoung Seop Kim
Keyword(s):  
Dynamic Recovery ◽  
High Pressure Torsion ◽  
Radial Strain ◽  
Positron Annihilation Spectroscopy ◽  
Structure Evolution ◽  
Fine Grained ◽  
Angular Pressing ◽  
Structure Changes ◽  
Transmission Electron ◽  
Fine Grained Structure

Commercial MgAlZn alloy AZ31 was processed by two techniques of severe plastic deformation, namely equal channel angular pressing (ECAP) and high pressure torsion (HPT). Microstructure evolution with strain due to ECAP and HPT was investigated by light and transmission electron microscopy (TEM). Significant grain refinement was observed in specimens processed both by ECAP and HPT. Moreover, HPT resulted in radial strain and microstructure inhomogeneity across the diameter of the sample disk. This inhomogeneity was continuously smeared out and almost homogeneous ultra-fine grained structure was observed in specimen subjected to 15 HPT rotations. Dislocation structure changes in individual specimens after different number of ECAP passes and HPT rotations were investigated by positron annihilation spectroscopy (PAS). Sharp increase of dislocation density occurred during the first two passes of ECAP, followed by the saturation and even a decline manifesting the dynamic recovery at higher strains.

High Pressure Torsion of Intermetallic Zr3Al

2008 ◽  
Vol 584-586 ◽  
pp. 553-558 ◽  
Author(s):  
David Geist ◽  
Christian Rentenberger ◽  
Hans Peter Karnthaler
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Structural Evolution ◽  
Nanocrystalline Structure ◽  
Temperature Dependent ◽  
Transmission Electron ◽  
Ordered Alloys ◽  
Grain Fragmentation ◽  
Shear Strains

The L12-structured intermetallic compound Zr3Al can be rendered amorphous easily by several techniques. In the present study the structural evolution during high pressure torsion (HPT) was investigated systematically by transmission electron microscopy (TEM) methods. Zr3Al samples were deformed at room temperature to different grades of deformation up to shear strains of 140 000%. TEM investigations revealed that the tendency to grain fragmentation, disordering and the formation of a nanocrystalline structure is weak compared to other L12 ordered alloys like Ni3Al. In addition, an amorphous phase has not been encountered. The present results differ strongly from previous ones obtained from ball-milled materials. Possible reasons for the different behavior are discussed on the basis of the temperature dependent dissociation scheme of the superlattice dislocations gliding in Zr3Al.

Influence of Initial Heat Treatment on the Microhardness Evolution of an Al-Mg-Sc Alloy Processed by High-Pressure Torsion

2016 ◽  
Vol 879 ◽  
pp. 1471-1476 ◽  
Author(s):  
Pedro Henrique R. Pereira ◽  
Yi Huang ◽  
Terence G. Langdon
Keyword(s):  
Heat Treatment ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Solution Treatment ◽  
Equivalent Strain ◽  
Microhardness Distribution ◽  
Solution Treated ◽  
Mg Content ◽  
Initial Heat ◽  
Initial Heat Treatment

An Al-3% Mg-0.2% Sc alloy was subjected to annealing or solution treatment and further processed by HPT at room temperature. Microhardness measurements were taken along the middle-sections of the discs and they demonstrated that a very substantial hardening is achieved during HPT processing regardless of the initial heat treatment. Hardness values of ~200 Hv were recorded at the edge of the samples although the microhardness distribution remained inhomogeneous along the diameters of the discs after 20 turns of high-pressure torsion. In addition, the microhardness of the solution treated Al-Mg-Sc samples continued to increase with the equivalent strain imposed by the anvils even after 30 turns of HPT processing whereas the hardness at the edges of the annealed discs saturated after 10 turns. These differences in the hardness evolution are attributed to the higher Mg content in solid solution in the case of the solution treated samples and its influence on delaying the recovery rate of this aluminium alloy.

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.

Aging Behavior of Cu-Ni-Si Alloy Processed by High-Pressure Torsion

2010 ◽  
Vol 667-669 ◽  
pp. 307-312 ◽  
Author(s):  
Hirotaka Matsunaga ◽  
Z. Horita ◽  
Kazutaka Imamura ◽  
Takanobu Kiss ◽  
Xavier Sauvage
Keyword(s):  
Electrical Conductivity ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Three Dimensional ◽  
Aging Treatment ◽  
Atom Probe ◽  
Appreciable Amount ◽  
Aging Behavior ◽  
Transmission Electron ◽  
20 Nm

An age-hardenable Cu-2.9%Ni-0.6%Si alloy was subjected to high-pressure torsion. Aging behavior was investigated in terms of hardness, electrical conductivity and microstructural features. Transmission electron microscopy showed that the grain size is refined to ~150 nm and the Vickers microhardness was significantly increased through the HPT process. Aging treatment of the HPT-processed alloy led to a further increase in the hardness. Electrical conductivity is also improved with the aging treatment. It was confirmed that the simultaneous strengthening by grain refinement and fine precipitation is achieved while maintaining high electrical conductivity. Three dimensional atom probe analysis revealed that fine precipitates with sizes of ~20 nm or smaller were formed in the Cu matrix and some particles consist of Ni and Si with no appreciable amount of Cu.

Aging Behavior of Al-Mg-Si Alloys Processed by High-Pressure Torsion

2010 ◽  
Vol 667-669 ◽  
pp. 259-264 ◽  
Author(s):  
Daichi Akama ◽  
Z. Horita ◽  
Kenji Matsuda ◽  
Shoichi Hirosawa
Keyword(s):  
High Pressure ◽  
Grain Refinement ◽  
High Pressure Torsion ◽  
Aging Behavior ◽  
Additional Element ◽  
Total Period ◽  
Grain Sizes ◽  
Solution Treated ◽  
Transmission Electron ◽  
Alloying Compositions

This research investigates simultaneous strengthening by grain refinement and fine precipitation in age-hardenable Al-Mg-Si alloys containing an additional element of either Ag, Cu, Pt or Pd. The alloys were solution-treated and processed by high-pressure torsion (HPT) at room temperature under a pressure of 6 GPa. They were aged at a temperature of 373 K for up to a total period of 6.7 hours. Vickers microhardness was measured after selected periods of aging and the microstructures were observed by transmission electron microscopy. It was found that, in all alloys, the grain sizes after HPT were refined to 300-400 nm and there were significant increases in the hardness through the HPT processing. The hardness was further increased by the subsequent ageing treatment, confirming the simultaneous strengthening by grain refinement and fine precipitation. However, the aging behavior was different depending on the alloying compositions.

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