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Norwegian University of Science and Technology
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Papers by khelfa tarek
The International Journal of Advanced Manufacturing Technology, 2017
An ultrafine grained Al-Mg-Si alloy was prepared by severe plastic deformation using the Equal Ch... more An ultrafine grained Al-Mg-Si alloy was prepared by severe plastic deformation using the Equal Channel Angular Pressing (ECAP) method. Samples were ECAPed through a die with an inner angle of Φ=90º and outer arc of curvature of ψ= 37° from 1 to 12 ECAP passes at room temperature following route Bc. To analyze the evolution of the microstructure at increasing ECAP passes x-ray diffraction and Electron Backscatter Diffraction analyses were carried out. The results revealed two distinct processing regimes, namely: i) from 1 to 5 passes, the microstructure evolved from elongated grains and sub-grains to a rather equiaxed array of ultrafine grains and ii) from 5 to 12 passes where no change in the morphology and average grain size was noticed. In the overall behavior, the boundary misorientation angle and the fraction of high-angle boundaries increase rapidly up to 5 passes and at a lower rate from 5 to 12 passes. The crystallite size decreased down to about 45 nm with the increase in deformation. The influence of deformation on precipitate evolution in the Al-Mg-Si alloy was also studied by differential scanning calorimetry. A significant decrease in the peak temperature associated to the 50% of recrystallization was observed at increasing ECAP passes.
Journal of Materials Engineering and Performance, 2021
AA6060 aluminum alloy was subjected to severe plastic deformation through equal-channel angular p... more AA6060 aluminum alloy was subjected to severe plastic deformation through equal-channel angular pressing (ECAP) up to 8 passes via route BC. ECAPed samples isochronally annealed for 1 hour at a temperature range of 150-450 °C. The microstructure and texture of the studied material were evaluated by electron backscatter diffraction, and the microhardness was characterized by Vickers microhardness testing. It was found that shearing texture is typically enhanced after ECAP processing. Grain size and grain growth kinetics were also studied. ECAP led to a substantial rise in hardness, with stability following 4 passes. Microstructures and material properties were relatively stable up to annealing temperatures of 150 °C. Some sub-micrometer grains were kept in the 8 passes sample to annealing temperatures of 300 °C. Annealing at elevated temperature resulted in a reduction in hardness leading to a rise in grain size and a decrease in dislocation density. After annealing temperature up to 450 °C, the texture index reveals a tendency to the texture weakening and randomization. The activation energy required for the grain growth of the AA6060 alloy was exceptionally low above 300 °C.
Acta Materialia, 2011
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Journal of Materials Engineering and Performance
Journal of Materials Engineering and Performance
Advanced Engineering Materials
Engineering Fracture Mechanics
The International Journal of Advanced Manufacturing Technology, 2017
An ultrafine grained Al-Mg-Si alloy was prepared by severe plastic deformation using the Equal Ch... more An ultrafine grained Al-Mg-Si alloy was prepared by severe plastic deformation using the Equal Channel Angular Pressing (ECAP) method. Samples were ECAPed through a die with an inner angle of Φ=90º and outer arc of curvature of ψ= 37° from 1 to 12 ECAP passes at room temperature following route Bc. To analyze the evolution of the microstructure at increasing ECAP passes x-ray diffraction and Electron Backscatter Diffraction analyses were carried out. The results revealed two distinct processing regimes, namely: i) from 1 to 5 passes, the microstructure evolved from elongated grains and sub-grains to a rather equiaxed array of ultrafine grains and ii) from 5 to 12 passes where no change in the morphology and average grain size was noticed. In the overall behavior, the boundary misorientation angle and the fraction of high-angle boundaries increase rapidly up to 5 passes and at a lower rate from 5 to 12 passes. The crystallite size decreased down to about 45 nm with the increase in deformation. The influence of deformation on precipitate evolution in the Al-Mg-Si alloy was also studied by differential scanning calorimetry. A significant decrease in the peak temperature associated to the 50% of recrystallization was observed at increasing ECAP passes.
Journal of Materials Engineering and Performance, 2021
AA6060 aluminum alloy was subjected to severe plastic deformation through equal-channel angular p... more AA6060 aluminum alloy was subjected to severe plastic deformation through equal-channel angular pressing (ECAP) up to 8 passes via route BC. ECAPed samples isochronally annealed for 1 hour at a temperature range of 150-450 °C. The microstructure and texture of the studied material were evaluated by electron backscatter diffraction, and the microhardness was characterized by Vickers microhardness testing. It was found that shearing texture is typically enhanced after ECAP processing. Grain size and grain growth kinetics were also studied. ECAP led to a substantial rise in hardness, with stability following 4 passes. Microstructures and material properties were relatively stable up to annealing temperatures of 150 °C. Some sub-micrometer grains were kept in the 8 passes sample to annealing temperatures of 300 °C. Annealing at elevated temperature resulted in a reduction in hardness leading to a rise in grain size and a decrease in dislocation density. After annealing temperature up to 450 °C, the texture index reveals a tendency to the texture weakening and randomization. The activation energy required for the grain growth of the AA6060 alloy was exceptionally low above 300 °C.
Acta Materialia, 2011
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Journal of Materials Engineering and Performance
Journal of Materials Engineering and Performance
Advanced Engineering Materials
Engineering Fracture Mechanics