The Effect of Strain Reversal during High Pressure Torsion on the Evolution of Microstructure and Hardness in Al-2.5wt% Mg alloy

Experiments were conducted on copper subjected to High Pressure Torsion to investigate the evolution of microstructure and microhardness with shear strain, γ. Observations have been carried out in the longitudinal section for a proper demonstration of the structure morphology. An elongated dislocation cell/subgrain structure was observed at relatively low strain level. With increasing strain, the elongated subgrains transformed into elongated grains and finally into equiaxed grains with high angle grain boundaries. Measurements showed the hardness increases with increasing γ then tends to saturations when γ >5. The variation tendency of microhardness with γ can be simulated by Voce-type equation.

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Evolution of microstructure and hardness during artificial aging of an ultrafine-grained Al-Zn-Mg-Zr alloy processed by high pressure torsion

Journal of Materials Science ◽

10.1007/s10853-020-05264-4 ◽

2020 ◽

Vol 55 (35) ◽

pp. 16791-16805

Author(s):

Jenő Gubicza ◽

Moustafa El-Tahawy ◽

János L. Lábár ◽

Elena V. Bobruk ◽

Maxim Yu Murashkin ◽

...

Keyword(s):

High Pressure ◽

Dislocation Density ◽

Grain Boundaries ◽

Artificial Aging ◽

High Pressure Torsion ◽

Secondary Phase ◽

Aging Effect ◽

Angular Pressing ◽

Ultrafine Grained ◽

Evolution Of Microstructure

Abstract An ultrafine-grained (UFG) Al-4.8%Zn-1.2%Mg-0.14%Zr (wt%) alloy was processed by high pressure torsion (HPT) technique and then aged at 120 and 170 °C for 2 h. The changes in the microstructure due to this artificial aging were studied by X-ray diffraction and transmission electron microscopy. It was found that the HPT-processed alloy has a small grain size of about 200 nm and a high dislocation density of about 8 × 1014 m−2. The majority of precipitates after HPT are Guinier–Preston (GP) zones with a size of ~ 2 nm, and only a few large particles were formed at the grain boundaries. Annealing at 120 and 170 °C for 2 h resulted in the formation of stable MgZn2 precipitates from a part of the GP zones. It was found that for the higher temperature the fraction of the MgZn2 phase was larger and the dislocation density in the Al matrix was lower. The changes in the precipitates and the dislocation density due to aging were correlated to the hardness evolution. It was found that the majority of hardness reduction during aging was caused by the annihilation of dislocations and some grain growth at 170 °C. The aging effect on the microstructure and the hardness of the HPT-processed specimen was compared to that observed for the UFG sample processed by equal-channel angular pressing. It was revealed that in the HPT sample less secondary phase particles formed in the grain boundaries, and the higher amount of precipitates in the grain interiors resulted in a higher hardness even after aging.

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Age-hardening of an Al–Li–Cu–Mg alloy (2091) processed by high-pressure torsion

Materials Science and Engineering A ◽

10.1016/j.msea.2012.03.029 ◽

2012 ◽

Vol 546 ◽

pp. 82-89 ◽

Cited By ~ 39

Author(s):

Seungwon Lee ◽

Zenji Horita ◽

Shoichi Hirosawa ◽

Kenji Matsuda

Keyword(s):

High Pressure ◽

High Pressure Torsion ◽

Mg Alloy ◽

Age Hardening

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Microstructural Evolution and Structure-Hardness Relationship in an Al-4wt.%Mg Alloy Processed by High-Pressure Torsion

Journal of Materials Engineering and Performance ◽

10.1007/s11665-016-2044-1 ◽

2016 ◽

Vol 25 (5) ◽

pp. 1909-1915 ◽

Cited By ~ 8

Author(s):

Xiaohui Yang ◽

Jianhong Yi ◽

Song Ni ◽

Yong Du ◽

Min Song

Keyword(s):

High Pressure ◽

Microstructural Evolution ◽

High Pressure Torsion ◽

Mg Alloy

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Application of High-Pressure Sliding for Grain Refinement of Al and Mg Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.667-669.91 ◽

2010 ◽

Vol 667-669 ◽

pp. 91-96 ◽

Cited By ~ 7

Author(s):

Kiyonari Tazoe ◽

Shuji Honda ◽

Z. Horita

Keyword(s):

High Pressure ◽

Strain Rate ◽

Grain Refinement ◽

High Pressure Torsion ◽

Initial Strain Rate ◽

Mg Alloys ◽

Initial Strain ◽

Mg Alloy ◽

Al Alloy ◽

Average Grain Size

An earlier study showed that high-pressure sliding (HPS) is effective for grain refinement of pure Al in a rectangular sheet form using the principle of high-pressure torsion. In this study, the HPS is applied for grain refinement of an Al-3%Mg-0.2%Sc alloy and an AZ61 Mg alloy. HPS was conducted under a pressure of 1 GPa with sliding distances of 10 to 30 mm at room temperature for the Al alloy and at 473 K for the Mg alloy The average grain size is ~300 nm for both the Al and Mg alloys, respectively. Tensile tests showed that a superplastic elongation of ~1500% is achieved in the Al-3%Mg-0.2%Sc alloy at 573 K with an initial strain rate of 3.3x10-3 s-1 and of ~600% in the AZ61 alloy at 573 K with an initial strain rate of 1x10-3 s-1.

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Evolution of microstructure and hardness in aluminum processed by High Pressure Torsion Extrusion

Materials Science and Engineering A ◽

10.1016/j.msea.2019.138074 ◽

2019 ◽

Vol 762 ◽

pp. 138074 ◽

Cited By ~ 1

Author(s):

Babak Omranpour ◽

Yulia Ivanisenko ◽

Roman Kulagin ◽

Lembit Kommel ◽

E. Garcia Sanchez ◽

...

Keyword(s):

High Pressure ◽

High Pressure Torsion ◽

Evolution Of Microstructure

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Aging Behavior of Al-Li-Cu-Mg Alloy Processed by High-Pressure Torsion

Materials Science Forum ◽

10.4028/www.scientific.net/msf.654-656.1243 ◽

2010 ◽

Vol 654-656 ◽

pp. 1243-1246 ◽

Cited By ~ 1

Author(s):

Seung Won Lee ◽

Daichi Akama ◽

Z. Horita ◽

Tetsuya Masuda ◽

Shoichi Hirosawa ◽

...

Keyword(s):

High Pressure ◽

High Pressure Torsion ◽

Solution Treatment ◽

Aging Treatment ◽

Rolling Process ◽

Mg Alloy ◽

Age Hardening ◽

Subsequent Aging ◽

Solid Solution Treatment ◽

Conventional Rolling

This study presents an application of high-pressure torsion (HPT) to an Al-Li-Cu-Mg alloy (2091). The alloy was subjected to solid solution treatment at 505oC for 30 minutes and was processed by HPT under 6 GPa for 5 revolutions at room temperature. The hardness increased with straining and saturated to a constant level at 225 Hv. Aging was undertaken on the HPT-processed alloy at 100, 150 and 190oC for the total periods up to 9.3 days. The aging treatment led to a further increase in the hardness to ~275 Hv. It is shown that the simultaneous strengthening of the alloy due to grain refinement and age hardening was successfully achieved by application of HPT and subsequent aging treatment. The enhancement of the strength is prominent when compared with the application of a conventional rolling process.

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