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.

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.

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.

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 Is Superplasticity in the Future of Nanophase Materials?

1990 ◽  
Vol 196 ◽  
Author(s):  
R. W. Siegel
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Room Temperature ◽  
Grain Boundary Sliding ◽  
Atomic Clusters ◽  
Diffusional Creep ◽  
Ultrafine Grain ◽  
Grain Sizes ◽  
Nanophase Materials ◽  
Boundary Sliding

ABSTRACTThe ultrafine grain sizes and high diffusivities in nanophase materials assembled from atomic clusters suggest that these materials may have a strong tendency toward superplastic mechanical behavior. Both small grain size and enhanced diffusivity can be expected to lead to increased diffusional creep rates as well as to a significantly greater propensity for grain boundary sliding. Recent mechanical properties measurements at room temperature on nanophase Cu, Pd, and TiO2, however, give no indications of superplasticity. Nonetheless, significant ductility has been clearly demonstrated in these studies of both nanophase ceramics and metals. The synthesis of cluster-assembled nanophase materials is described and the salient features of what is known of their structure and mechanical properties is reviewed. Finally, the answer to the question posed in the title is addressed.

scholarly journals Effect of Grain Size on Carburization Characteristics of the High-Entropy Equiatomic CoCrFeMnNi Alloy

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7199
Author(s):  
Hyunbin Nam ◽  
Jeongwon Kim ◽  
Namkyu Kim ◽  
Sangwoo Song ◽  
Youngsang Na ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Grain Sizes ◽  
Fine Grain ◽  
Cast Specimen ◽  
Vacuum Carburization ◽  
Cold Rolled ◽  
Face Centered

In this study, the carburization characteristics of cast and cold-rolled CoCrFeMnNi high-entropy alloys (HEAs) with various grain sizes were investigated. All specimens were prepared by vacuum carburization at 940 °C for 8 h. The carburized/diffused layer was mainly composed of face-centered cubic structures and Cr7C3 carbide precipitates. The carburized/diffused layer of the cold-rolled specimen with a fine grain size (~1 μm) was thicker (~400 μm) than that of the carburized cast specimen (~200 μm) with a coarse grain size (~1.1 mm). In all specimens, the carbides were formed primarily through grain boundaries, and their distribution varied with the grain sizes of the specimens. However, the carbide precipitates of the cast specimen were formed primarily at the grain boundaries and were unequally distributed in the specific grains. Owing to the non-uniform formation of carbides in the carburized cast specimen, the areas in the diffused layer exhibited various carbide densities and hardness distributions. Therefore, to improve the carburization efficiency of equiatomic CoCrFeMnNi HEAs, it is necessary to refine the grain sizes.

Simulation of the interaction of plastic zone dislocations with the grain boundary at brittle-plastic transition temperatures in molybdenum

2021 ◽  
Vol 2021 (3) ◽  
pp. 77-85
Author(s):  
K. M. Borysovska ◽  
◽  
N. M. Marchenko ◽  
Yu. M. Podrezov ◽  
S. O. Firstov ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
Grain Boundary ◽  
Plastic Zone ◽  
Grain Boundaries ◽  
Crack Tip ◽  
Dynamics Simulation ◽  
Density Of Dislocations ◽  
Grain Sizes ◽  
Pile Up

The (DD) method was used to model the formation of the plastic zone of the top of the cracks in polycrystalline molybdenum. Special attention was paid to take into account the interaction of dislocations in the plastic zone with grain boundaries. Structural sensitivity of fracture toughness was analyzed under brittle-ductile condition. Simulations were performed for a range of grain sizes from 400 to 100 μm, at which a sudden increase in fracture toughness with a decrease of grain size was experimentally shown. We calculated the value of K1c taking into account the shielding action of dislocations. The position of all dislocations in the plastic zone at fracture moment was calculated. Based on these data, we obtained the dependences of dislocation density on the distance from the crack tip thereby confirming significant influence of the grain boundaries on plastic zone formation. At large grain sizes, when the plastic zone does not touch the boundary, the distribution of dislocations remained unchanged. As grains reduce their size to size of the plastic zone, they start formating a dislocation pile – up near the boundaries. Dislocations on plastic zone move slightly toward the crack tip, but the density of dislocations in the middle of the grain remains unchanged, and fracture toughness remains almost unchanged. Further reduction of the grain size leads to the Frank-Reed source activation on the grain boundary Forming dislocation pile-up of the neighbor grains. Its stress concentration acts on dislocations of the first grain and causes redistribution of plastic zone dislocations. If the reduction in grain size is not enough to form a strong pile-up, density of dislocations on plastic zone increases slightly and crack resistance increases a few percent. Further reduction of grains promotes strong pile-up, dislocations move to crack tip, and its density on plastic zone increases. Crack is shielded and fracture toughness increases sharply. The calculation showed that the fracture toughness jump is observed at grain sizes of 100—150 μm, in good agreement with the experiment. Keywords: dislocation dynamics simulation, molybdenum, fracture toughness, grain size, plastic zone, brittle-ductile transition.

Effect of Trace Boron Addition on the Microstructure and Tensile Elongation of Ti2AlNb-Based Orthorhombic Titanium Alloys

2010 ◽  
Vol 638-642 ◽  
pp. 1439-1444
Author(s):  
Masuo Hagiwara ◽  
Tomoyuki Kitaura
Keyword(s):  
Grain Size ◽  
Room Temperature ◽  
Tensile Elongation ◽  
Boron Addition ◽  
Grain Sizes ◽  
Solution Treated Condition ◽  
Room Temperature Ductility ◽  
Solution Treated ◽  
Treated Condition ◽  
Orthorhombic Titanium

The grain sizes of two kinds of orthorhombic alloys, namely (O+B2) Ti-22Al-11Nb-2Mo -1Fe and (O+2) Ti-27.5Al-13Nb have been successfully reduced by the addition of trace boron (B) (less than 0.12 wt.%). For example, the grain size in the B2 solution-treated condition was reduced from 1 mm to 80 m by the addition of 0.05% B for both alloys. The tensile elongation of Ti-22Al-11Nb-2Mo-1Fe at room temperature and 650C was increased from 0.3% to 4.3%, and from 8.2% to 30.3%, respectively, by the addition of 0.10% B. Ti-27.5Al-13Nb also showed an improved room temperature ductility by the minor B addition.

scholarly journals Microstructural Evolution and Mechanical Properties of Friction Stir Welded Butt Joints of 5A06 Alloy Ultra-Thin Sheets

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3906 ◽  
Author(s):  
Yang Han ◽  
Xiaoqing Jiang ◽  
Tao Yuan ◽  
Shujun Chen ◽  
Dongxiao Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Welding Speed ◽  
Base Material ◽  
Thin Plates ◽  
Al Alloy ◽  
Minimum Thickness ◽  
Friction Stir

Ultra-thin plates have great potential for applications in aircraft skin, the packaging industry, and packaging of electronic products. Herein, 1 mm-thick 5A06 Al alloy was welded with friction stir welding. The microstructural evolution of the welds was investigated in detail with optical microscopy, scanning electron microscopy, and electron backscatter diffraction. The results showed that the friction stir welds of 1 mm-thick 5A06 Al alloy were well formed without obvious defect and with a minimum thickness reduction of 0.025 mm. Further, the grain size and the proportion of low-angle grain boundaries decreased with decreasing welding speed, because of the increasing degree of dynamic recrystallization. Among all of the welded joints, the welding speed of 100 mm/min yielded the smallest grain size and the highest proportion of high-angle grain boundaries, and thus the best mechanical properties. Specifically, the tensile strength of the joint was greater than that of the base material, while the elongation reached 80.83% of the base material.

scholarly journals Mechanical and Electrical Characteristics of WB2 Synthesized at High Pressure and High Temperature

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1212 ◽  
Author(s):  
Changchun Wang ◽  
Lele Song ◽  
Yupeng Xie
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Electrical Resistivity ◽  
High Temperature ◽  
Vickers Hardness ◽  
Single Phase ◽  
Hard Material ◽  
Experimental Conditions ◽  
Boundary Density ◽  
Grain Sizes

Single-phase tungsten diboride (WB2) was synthesized at high pressure and high temperature. The different grain sizes ranging from 300 nm to 3 µm were successfully obtained in WB2 by controlling the experimental conditions. The effects of grain size on hardness and resistivity properties were investigated. The Vickers hardness of WB2 was modulated with grain size. The maximum asymptotic Vickers hardness is 25.5 GPa for WB2 with a grain size of 300 nm which is a 10% increase compared to WB2 with a grain size of 3 µm. The optimal electrical resistivity of WB2 was 10−7 Ωm with the biggest grain size of 3 µm, which is ascribed to low grain boundary density. The superior properties of hardness and electrical resistivity demonstrate that WB2 should be a new functional hard material replacing WC which is widely used in industrial production.

Dielectric Properties of Nanograined BaTiO3 Ceramics Fabricated by Aerosol Deposition Method

2011 ◽  
Vol 485 ◽  
pp. 183-186 ◽  
Author(s):  
Tsutomu Furuta ◽  
Saki Hatta ◽  
Yoichi Kigoshi ◽  
Takuya Hoshina ◽  
Hiroaki Takeda ◽  
...  
Keyword(s):  
Grain Size ◽  
Room Temperature ◽  
Annealing Treatment ◽  
Aerosol Deposition ◽  
Dielectric Measurement ◽  
Deposition Method ◽  
Grain Sizes ◽  
Average Grain Size ◽  
Aerosol Deposition Method ◽  
Polarization Electric Field

Freestanding BaTiO3 ceramics films were fabricated using the aerosol deposition (AD) method and the size effect of nanograined BaTiO3 ceramics was demonstrated. Dense BaTiO3 thick film fabricated by the AD method was crystallized and detached from substrate by an annealing treatment at 600 °C, and then the grain size was controlled by a reannealing treatment at various temperatures. As a result, freestanding BaTiO3 thick films with various grain sizes from 24 to 170 nm were successfully obtained. Polarization–electric field (P–E) measurement revealed that BaTiO3 ceramics with grain sizes of more than 58 nm showed ferroelectricity, whereas BaTiO3 ceramics with an average grain size of 24 nm showed paraelectricity at room temperature. Dielectric measurement indicated that the permittivity decreased with decreasing grain size in the range of 170 to 24 nm.

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