Application of High-Pressure Torsion to Al-Si Alloys with and without Scandium Additions

2010 ◽  
Vol 667-669 ◽  
pp. 743-748 ◽  
Author(s):  
K. Venkateswarlu ◽  
V. Rajinikanth ◽  
Mani Kuntal Sen ◽  
Saleh N. Alhajeri ◽  
Terence G. Langdon
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Grain Structure ◽  
Ball Indentation ◽  
Grain Formation ◽  
The Difference ◽  
Hardness Values ◽  
Microstructural Examination

Al-2 wt. % Si alloys with and without 0.25 wt. % scandium additions were processed by high-pressure torsion up to five turns at room temperature under a pressure of 6.0 GPa. Microstructural examination of the as-cast Al-2Si-0.25Sc alloy revealed the presence of Al3Sc precipitates which refined the Al grain structure, whereas no major changes were observed in the morphology of the Si particles. Processing by HPT of both experimental alloys revealed submicrometer grains with uniformly distributed Si particles. The mechanical properties were obtained using hardness measurements and the ball-indentation technique. The results show the hardness increased in the first turn of HPT and further increased with increasing numbers of turns. In addition, the hardness values were lower at the centers and continuously increased towards the edges of the disks. The difference in hardness values between the centre and the edge decreased with increasing turns, thereby suggesting an increasing homogeneity with increasing processing. The scandium addition and HPT processing of the Al-2Si alloy strongly influences the grain refinement and mechanical properties. The grain size reduction in the Al-2Si alloy was similar to Al whereas the presence of Sc in Al-2Si during HPT processing was responsible for large precipitation networks and a submicrometer grain formation.

Mechanical Behavior of a Metal Matrix Nanocomposite Synthesized by High-Pressure Torsion via Diffusion Bonding

2016 ◽  
Vol 879 ◽  
pp. 1068-1073
Author(s):  
Han Joo Lee ◽  
Jae Kyung Han ◽  
Byung Min Ahn ◽  
Megumi Kawasaki ◽  
Terence G. Langdon
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Metal Matrix ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Ambient Temperatures ◽  
Metal Matrix Nanocomposite ◽  
Wide Range ◽  
Zk60 Magnesium Alloy ◽  
Matrix Nanocomposite

High-pressure torsion (HPT) is one of the major severe plastic deformation (SPD) procedures where disk metals generally achieve exceptional grain refinement at ambient temperatures. HPT has been applied for the consolidation of metallic powders and bonding of machining chips whereas very limited reports examined the application of HPT for the fabrication of nanocomposites. An investigation was initiated to evaluate the potential for the formation of a metal matrix nanocomposite (MMNC) by processing two commercial metal disks of Al-1050 and ZK60 magnesium alloy through HPT at room temperature. Evolutions in microstructure and mechanical properties including hardness and plasticity were examined in the processed disks with increasing numbers of HPT turns up to 5. This study demonstrates the promising possibility for using HPT to fabricate a wide range of hybrid MMNCs from simple metals.

Microstructural Evolution of Mg-4Nd Alloy Processed by High-Pressure Torsion

2010 ◽  
Vol 667-669 ◽  
pp. 391-396 ◽  
Author(s):  
Jing Bai ◽  
Feng Xue ◽  
Saleh N. Alhajeri ◽  
Terence G. Langdon
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Dislocation Density ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
High Angle ◽  
Sharp Rise ◽  
Large Numbers ◽  
Average Grain Size ◽  
Hardness Values

Disks of as-extruded Mg-4Nd alloy were processed by high-pressure torsion (HPT) through ¼ to 5 turns at room temperature. The first 1/4 turn of HPT induces large numbers of twins and some dislocation tangles in the center region of the disk. With increase of torsional straining, the twinning is inhibited gradually and the dislocation density increases relating to the formation of dislocation substructures and ultimately transforming to high fractions of equiaxed gains which have an average grain size of ~200 nm and high-angle boundaries. HPT significantly improves the values of microhardness of this alloy. The hardness values in both the central and edge regions show a sharp rise after HPT for 1/4 turn and exhibit nearly saturation after 1/2 turn although there is a trend of a slight increase with increasing numbers of turns. The experimental results suggest more homogeneous microstructures may be produced by larger numbers of turns in the HPT process.

Recovery or Non-Recovery in Al-0.1% Mg and Al-1% Mg Alloy during High-Pressure Torsion Processing

2016 ◽  
Vol 879 ◽  
pp. 773-778 ◽  
Author(s):  
Yi Huang ◽  
Justine Millet ◽  
Nian Xian Zhang ◽  
Pedro Henrique R. Pereira ◽  
Terence G. Langdon
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Mg Alloys ◽  
Rapid Recovery ◽  
Mg Alloy ◽  
Disc Diameter ◽  
Disc Centre ◽  
Evolution Behavior ◽  
Hardness Values

The Al-1% Mg and Al-0.1% Mg alloys were both processed by high-pressure torsion (HPT) at room temperature. In the Al-1% Mg alloy, the hardness values in the disc centre area are lower than in the disc edge area after 1/2 and 1 turn, and the area of lower hardness values in the disc centre decreases as the number of turns increases from 1/2 to 1 turn. Finally, the hardness values are reasonably homogenous along the disc diameter as the number of turns increases to 5 and 10 turns. The Al-0.1% Mg alloy displays a different hardness evolution behavior: the hardness values in the disc centre are higher than at the disc edge 1/2 and 1 turn, and the area of higher hardness values decreases as the numbers of turn increases from 1/2 to 1 turn. The hardness values evolve towards homogeneity along the disc diameter after 5 and 10 turns. EBSD microstructure investigations in the Al-0.1% Mg alloy reveal that a few low-angle boundaries exist at the disc edge after 1/2 turn. It is suggested that the higher hardness values in the disc centre in the Al-0.1% Mg alloy are related to rapid recovery at the disc edge where the material is subjected to heavy straining.

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.

Microstructure Evolution during High Pressure Torsion of AZ80 Magnesium Alloy

2008 ◽  
Vol 584-586 ◽  
pp. 300-305 ◽  
Author(s):  
Dogan Arpacay ◽  
Sang Bong Yi ◽  
Miloš Janeček ◽  
Adem Bakkaloglu ◽  
Lothar Wagner
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
High Pressure ◽  
Magnesium Alloy ◽  
Grain Refinement ◽  
Microstructure Evolution ◽  
Significant Variation ◽  
High Pressure Torsion ◽  
Grain Structure ◽  
Az80 Magnesium Alloy

The microstructure evolution during high pressure torsion and its influence on the mechanical properties of AZ80 magnesium alloy is presented in this study. Significant grain refinement was observed after high pressure torsion, while the homogeneity of the grain structure increases with the number of revolutions. Grain size decreases to about 50 nm after 15 revolutions. The microhardness profiles measured at through-thickness and through-width directions show no significant variation at different positions of the sample. Moreover, the negligible effect of the revolution number on the microhardness value was observed.

Using ball indentation to determine the mechanical properties of an Al-7475 alloy processed by high-pressure torsion

2012 ◽  
Vol 48 (13) ◽  
pp. 4773-4779 ◽  
Author(s):  
Deepak C. Patil ◽  
S. A. Kori ◽  
K. Venkateswarlu ◽  
Gautam Das ◽  
Saleh N. Alhajeri ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Ball Indentation

scholarly journals Microstructure and Mechanical Properties of Al-3 Vol% CNT Nanocomposites Processed by High-Pressure Torsion

2017 ◽  
Vol 62 (2) ◽  
pp. 1109-1112 ◽  
Author(s):  
H. Asgharzadeh ◽  
H.S. Kim
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
High Pressure ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Tensile Ductility ◽  
Tensile Tests ◽  
Tensile Fracture ◽  
Tensile Fracture Surface ◽  
Transmission Electron

Abstract Al-3 vol% CNT nanocomposites were processed by high-pressure torsion (HPT) at room temperature under the pressure in the range of 2.5-10 GPa for up to 10 turns. Optical microscopy, scanning electron microscopy, and transmission electron microscopy (TEM) were used to investigate the microstructural evolutions upon HPT. Mechanical properties of the HPT-processed disks were studied using tensile tests and microhardness measurements. The results show gradual evolutions in the density, microstructure, and hardness with increasing the number of turns and applied presure. Nanostructured and elongated Al grains with an average grain thickness of ~40 nm perpendicular to the compression axis of HPT and an aspect ratio of ~3 are formed after 10 turns under 6 GPa. Evaluating the mechanical properties of the 10-turn processed Al/CNT nanocomposites indicates a tensile strength of 321 MPa and a hardness of 122 Hv. The tensile fracture surface of the Al/CNT nanocomposite mostly demonstrates a smooth fracture manner with fine dimples resulting in a low tensile ductility of ~1.5%.

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.

Grain Refinement and Deformation Behavior of Ultrafine Grained Pd and Pd-Ag Alloys Produced by HPT

2008 ◽  
Vol 584-586 ◽  
pp. 182-187
Author(s):  
Lilia Kurmanaeva ◽  
Yulia Ivanisenko ◽  
J. Markmann ◽  
Ruslan Valiev ◽  
Hans Jorg Fecht
Keyword(s):  
Mechanical Properties ◽  
Deformation Behavior ◽  
Materials Science ◽  
High Pressure Torsion ◽  
Uniform Elongation ◽  
Grain Structure ◽  
Coarse Grained ◽  
Ultrafine Grain ◽  
Ultrafine Grained ◽  
Ultrafine Grain Structure

Investigations of mechanical properties of nanocrystalline (nc) materials are still in interest of materials science, because they offer wide application as structural materials thanks to their outstanding mechanical properties. NC materials demonstrate superior hardness and strength as compared with their coarse grained counterparts, but very often they possess a limited ductility or show low uniform elongation due to poor strain hardening ability. Here, we present the results of investigation of the microstructure and mechanical properties of nc Pd and Pd-x%Ag (x=20, 60) alloys. The initially coarse grained Pd-x% Ag samples were processed by high pressure torsion, which resulted in formation of homogenous ultrafine grain structure. The increase of Ag contents led to the decrease of the resulted grain size and change in deformation behavior, because of decreasing of stacking fault energy (SFE). The samples with larger Ag contents demonstrated the higher values of hardness, yield stress and ultimate stress. Remarkably the uniform elongation had also increased with increase of strength.

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