Microstructures and Mechanical Property of Ni Processed by High-Pressure Torsion and Their Evolution upon Annealing

2006 ◽  
Vol 114 ◽  
pp. 45-50 ◽  
Author(s):  
Zhi Qing Yang
Keyword(s):  
High Pressure ◽  
Grain Boundaries ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Small Difference ◽  
Dynamical Evolution ◽  
Peripheral Region ◽  
Lattice Defects ◽  
Grain Sizes ◽  
Xrd And Tem

XRD, TEM, microhardness and thermal analysis were carried out on a series of Ni samples produced by high-pressure torsion (HPT). The evolution of microstructures and their inhomogeneity were investigated. The local microstrain showed dynamical oscillations as a function of the HPT rotations, demonstrating dynamical evolution of lattice defects during the procedure. Both XRD and TEM showed that a small difference in grain sizes remains even after 5 revolutions of HPT with smaller grain sizes at the peripheral region of the sample. The higher microhardness at the peripheral region is the result of the smaller grain sizes and the higher density of lattice defects, compared with the central region. Thermal treatment at a heating rate of 20K/min from room temperature to 473K did not result in decreased microhardness, but increased by about 10% for samples treated with not more than 3 rotations of HPT. The increase in microhardness was attributed to further grain refinement, the formation of a larger fraction of high-angle grain boundaries and grain boundaries being closer to equilibrium after recovery.

Application of High Pressure Torsion to Bulk Samples

2006 ◽  
Vol 503-504 ◽  
pp. 391-398 ◽  
Author(s):  
Genki Sakai ◽  
Katsuaki Nakamura ◽  
Z. Horita ◽  
Terence G. Langdon
Keyword(s):  
High Pressure ◽  
Tensile Testing ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Initial Strain Rate ◽  
Thin Disk ◽  
Metallic Materials ◽  
Grain Sizes ◽  
Angular Pressing ◽  
Cylindrical Samples

High pressure torsion (HPT) is a well-known procedure to impart severe plastic deformation (SPD) into metallic materials. It was reported that HPT produces grain sizes finer than those using other SPD processes such as equal-channel angular pressing (ECAP). However, the application of HPT has been restricted to thin disk samples. In this study, an HPT process was developed for use with bulk samples. This process is designated as Bulk-HPT for comparison with conventional Disk-HPT. Cylindrical samples of an Al-3%Mg-0.2%Sc alloy having dimensions of 10 mm in diameter and 8.6 mm in height were prepared for Bulk-HPT. The samples were strained under a pressure of 1 GPa for 2 turns at room temperature. Microstructural observations revealed that the samples contained regions having a grain size of ~130 nm. Tensile testing showed a superplastic ductility ~480 % at 673 K with an initial strain rate of 3.3x10-2 s-1.

Microstructure and Properties of a Fe-Cu Composite Processed by HPT Powder Consolidation

2010 ◽  
Vol 667-669 ◽  
pp. 229-234 ◽  
Author(s):  
Andrea Bachmaier ◽  
Reinhard Pippan
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Grain Size ◽  
High Pressure ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Step Process ◽  
Powder Consolidation ◽  
Grain Sizes ◽  
Scanning Electron

A method to produce nanocrystalline Fe-Cu composites by means of high-pressure torsion (HPT) deformation is presented. Mixtures of micrometer sized powders of Fe and Cu with different ratios of the two components were precompacted and subsequently deformed by HPT at room temperature to a certain amount of strain. Afterwards, new samples were cut out of these previously deformed samples and further HPT deformation was conducted. The evolution of the microstructure during the different steps of the HPT process and the resulting microstructure of the composites were investigated by scanning electron microscopy. In summary it could be shown that the final attainable grain sizes in the composite materials in the two step process are much smaller than in the simply HPT deformed composites. The reduction of the grain size is also reflected in an enhancement of the hardness.

Fabrication of submicrometer-grained Zn–22% Al by torsion straining

1996 ◽  
Vol 11 (9) ◽  
pp. 2128-2130 ◽  
Author(s):  
Minoru Furukawa ◽  
Zenji Horita ◽  
Minoru Nemoto ◽  
Ruslan Z. Valiev ◽  
Terence G. Langdon
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Grain Boundaries ◽  
Melting Temperature ◽  
Room Temperature ◽  
Equilibrium Configuration ◽  
Internal Stresses ◽  
Al Alloy ◽  
Grain Sizes ◽  
Very High

The Zn–22% Al eutectoid alloy is capable of exhibiting very high superplastic elongations, in excess of 2000% in tension, when the grain size is in the range of ∼ 1–10 μm. This paper describes the fabrication of a submicrometer grain size in the Zn–22% Al alloy by subjecting the samples to intense plastic straining in torsion under high pressure (∼5 GPa) at room temperature. Observations after straining revealed a heterogeneous microstructure with grain sizes in the range of ∼0.1–0.5 μm. As a result of the low melting temperature of the alloy, the high internal stresses introduced by torsion straining are relaxed and the grain boundaries are close to an equilibrium configuration.

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.

Deformation Twins Formed in Nanocrystalline Materials

2006 ◽  
Vol 503-504 ◽  
pp. 125-132 ◽  
Author(s):  
Yuntian T. Zhu
Keyword(s):  
Grain Boundaries ◽  
Nanocrystalline Materials ◽  
Partial Dislocation ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Nucleation And Growth ◽  
Analytical Models ◽  
Partial Dislocations ◽  
Deformation Twins ◽  
Low Strain Rate

Deformation twins have been oberved in nanocrystalline (NC) Al synthsized by cryogenic ball-milling and in NC Cu processed by high-pressure torsion under room temperature and at a very low strain rate. They were found formed by partial dislocations emitted from grain boundaries. This paper first reviews experimental evidences on deformation twinning and partial dislocation emissions from grain boundaries, and then discusses recent analytical models on the nucleation and growth of deformation twins. These models are compared with experimental results to establish their validity and limitations.

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.

scholarly journals Hardening mechanism of commercially pure Mg processed by high pressure torsion at room temperature

2014 ◽  
Vol 619 ◽  
pp. 95-106 ◽  
Author(s):  
Xiao Guang Qiao ◽  
Ya Wei Zhao ◽  
Wei Min Gan ◽  
Ying Chen ◽  
Ming Yi Zheng ◽  
...  
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Hardening Mechanism ◽  
Commercially Pure

scholarly journals The significance of self-annealing at room temperature in high purity copper processed by high-pressure torsion

2016 ◽  
Vol 656 ◽  
pp. 55-66 ◽  
Author(s):  
Yi Huang ◽  
Shima Sabbaghianrad ◽  
Abdulla I. Almazrouee ◽  
Khaled J. Al-Fadhalah ◽  
Saleh N. Alhajeri ◽  
...  
Keyword(s):  
High Pressure ◽  
High Purity ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Purity Copper

scholarly journals Intragranular deformation mechanisms in calcite deformed by high-pressure torsion at room temperature

2020 ◽  
Vol 114 (2) ◽  
pp. 105-118
Author(s):  
Roman Schuster ◽  
Gerlinde Habler ◽  
Erhard Schafler ◽  
Rainer Abart
Keyword(s):  
High Pressure ◽  
Twin Boundary ◽  
Brittle Failure ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Confining Pressure ◽  
Temperature Deformation ◽  
Orientation Relationships ◽  
High Confining Pressure ◽  
Confining Pressures

AbstractPolycrystalline calcite was deformed to high strain at room-temperature and confining pressures of 1–4 GPa using high-pressure torsion. The high confining pressure suppresses brittle failure and allows for shear strains >100. The post-deformation microstructures show inter- and intragranular cataclastic deformation and a high density of mechanical e$$ \left\{01\overline{1}8\right\} $$011¯8 twins and deformation lamellae in highly strained porphyroclasts. The morphologies of the twins resemble twin morphologies that are typically associated with substantially higher deformation temperatures. Porphyroclasts oriented unfavorably for twinning frequently exhibit two types of deformation lamellae with characteristic crystallographic orientation relationships associated with calcite twins. The misorientation of the first deformation lamella type with respect to the host corresponds to the combination of one r$$ \left\{10\overline{1}4\right\} $$101¯4 twin operation and one specific f$$ \left\{01\overline{1}2\right\} $$011¯2 or e$$ \left\{01\overline{1}8\right\} $$011¯8 twin operation. Boundary sections of this lamella type often split into two separated segments, where one segment corresponds to an incoherent r$$ \left\{10\overline{1}4\right\} $$101¯4 twin boundary and the other to an f$$ \left\{01\overline{1}2\right\} $$011¯2 or e$$ \left\{01\overline{1}8\right\} $$011¯8 twin boundary. The misorientation of the second type of deformation lamellae corresponds to the combination of specific r$$ \left\{10\overline{1}4\right\} $$101¯4 and f$$ \left\{01\overline{1}2\right\} $$011¯2 twin operations. The boundary segments of this lamella type may also split into the constituent twin boundaries. Our results show that brittle failure can effectively be suppressed during room-temperature deformation of calcite to high strains if confining pressures in the GPa range are applied. At these conditions, the combination of successive twin operations produces hitherto unknown deformation lamellae.

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