Structural phenomena induced in the course of and post low-temperature KOBO extrusion of AA6013 aluminum alloy

Korbel, A.; Pieła, K.; Ostachowski, Paweł; Łagoda, М.; Błaż, L.; Bochniak, W.; Pawlyta, Mirosława

doi:10.1016/j.msea.2017.10.095

Cited by 11 publications

(9 citation statements)

References 27 publications

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“…The severe deformation regime generates a high density of dislocations, solid solution strengthening due to the presence of alloying elements (such as Zn, Mg, Cu) in the Al matrix, dynamic softening, and dynamic recrystallization processes. The complex twisting-extrusion method (KOBO) seems optimal for Al alloys [12,13] because of combining monotonic extrusion, responsible for the Al profile shape formation, with excessive cyclically changing deformation (reverse twisting) [12]. Generally, the main advantage of the KOBO method is due to the specific die oscillation that results in an effective reduction in the processing energy and increases the processing efficiency [14].…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Mechanical Properties of Spark Plasma Sintered and Severely Deformed AA7075 Alloy

Garbiec¹,

Leshchynsky

García-Junceda

et al. 2021

Metals

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In this paper, the microstructure and mechanical properties of AA7075 with a coarse-fine-grained laminated microstructure produced by spark plasma sintering (SPS) and the cyclic extrusion severe deformation (KOBO) technique were investigated. It was found that an inhomogeneous grain microstructure was formed from coarse and fine grains by the SPS process and then was transformed into a coarse-fine-grained laminated microstructure by means of KOBO extrusion at room temperature. The grain refinement during KOBO extrusion resulted in a fine grained laminated microstructure created due to the formation of low-angle grain boundaries (LAGBs), followed by dynamic recrystallization, leading to high-angle grain boundaries (HAGBs). The EBSD analysis results reveal the formation of a deformed and partially recrystallized ultrafine grain microstructure owing to the generation and development of shear bands during KOBO extrusion. The ultimate tensile strength (UTS) of the AA7075 alloy rose after SPS-KOBO severe deformation up to 422 MPa, with high strains of about 33%. The obtained results clearly show that the SPS-KOBO extrusion technique allows a bimodal laminated fine gradient grain microstructure to be obtained due to deformation and dynamic recrystallization, which result in both high strength and good ductility. The new heterogeneous AA7075 alloys obtained by the SPS-KOBO combined techniques demonstrate that microstructural heterogeneities can assist in overcoming the strength–ductility trade-off.

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Section: Introductionmentioning

confidence: 99%

Microstructure and Mechanical Properties of Spark Plasma Sintered and Severely Deformed AA7075 Alloy

Garbiec¹,

Leshchynsky

García-Junceda

et al. 2021

Metals

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“…32). Some other SPD methods invented by Polish scientists were the KOBO method (a direct extrusion synchronized with the cyclically rotating die) 33,34) and semi-continuous incremental equal-channel angular pressing (I-ECAP), 35) which is a modified version of the equal-channel angular extrusion method introduced by Segal in 1981. 36)…”

Section: Erbel's Careermentioning

confidence: 99%

Historical Studies by Polish Scientist on Ultrafine-Grained Materials by Severe Plastic Deformation

Bryła

Edalati²

2019

Mater. Trans.

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Producing ultrafine-grained (UFG) materials by means of severe plastic deformation (SPD) methods has made a significant progress within the past few decades. The topic has been of interest since the beginning of the last century at least, yet the historical studies on this subject are less-known in the SPD society. In this manuscript, the studies of the Polish scientist Stanisław Erbel including his book entitled "Mechanism of Change of Properties of Metals Subjected to Large Deformations" written in 1976 are reviewed. Although American physicist Percy W. Bridgman published a book earlier on the principles of SPD in 1952, Erbel's book is probably the first book dedicated to the formation of UFG materials by SPD processing. In this book, Erbel presented details of a high-pressure torsion (HPT) device for obtaining large strains, mechanism of microstructural fragmentation during large straining, evolution of mechanical properties (hardness, tensile properties and torque), and characterization of the microstructure by means of transmission electron microscopy (TEM). The TEM studies included not only ex-situ observations but also in-situ observations to examine the dislocation motion and thermal stability.

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“…Their level depends on process parameters, particularly on the extrusion force, which reacts strongly to the frequency of die oscillation [39]. In turn, the process of KOBO extrusion of heat-treatable aluminum alloys eliminates their initial precipitation hardening of AA6013 [42], or as in the case of AA7075 alloy [71], "removes the effects of previous treatments." Meanwhile, the high hardness of Cu1Cr0.1Zr alloy, in commercial state, is preserved at a similar level in rods extruded by the KOBO method at low temperatures, and this parameter reacts weakly to annealing (aging).…”

Section: Commentarymentioning

confidence: 99%

“…Hardening of zinc and aluminum in the KOBO process was linked [40] to point defects with a highly non-equilibrial concentration. On the other hand, it was also acknowledged [42] that point defects could be the cause of softening of aluminum alloys, because when situated near precipitates, they relax the stresses originating from them. However, this concerns solely the case where all (nearly all) generated point defects are involved in the relaxation processes.…”

Section: Commentarymentioning

confidence: 99%

“…Particularly, the results presented in studies [35,36] indicate that KOBO extrusion of supersaturated CuCrZr alloy is not only an attractive metal forming process but also an effective means of influencing the products' mechanical properties. In the case of dispersion-hardened alloys, depending on the parameters of the KOBO process, one of two antagonistic phenomena occur [42]:…”

Section: Introductionmentioning

confidence: 99%

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Strength properties and structure of CuCrZr alloy subjected to low-temperature KOBO extrusion and heat treatment

Ostachowski

Bochniak

Łagoda

et al. 2019

Int J Adv Manuf Technol

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KOBO extrusion of metals and alloys strongly activates the point defect generation processes, as a result of which they reach a concentration exceeding the equilibrium level by many orders of magnitude. This leads to significant acceleration of diffusion phenomena which in heat-treatable alloys may cause disturbance of the thermodynamic equilibrium between the solid solution decomposition and dissolution of precipitates. In this work, measurements of mechanical and electrical properties and structural observations Cu1Cr0.1Zr alloy subjected to low-temperature KOBO extrusion at different stages of multi-variant heat treatment were conducted. In addition, the geometry of the extruded alloy's flow zone was analyzed and the obtained results made it possible to assess the effectiveness of experimental procedures, including product formation with high extrusion ratio λ, aimed at achieving of high and thermally stable functional properties of the material.

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Structural phenomena induced in the course of and post low-temperature KOBO extrusion of AA6013 aluminum alloy

Cited by 11 publications

References 27 publications

Microstructure and Mechanical Properties of Spark Plasma Sintered and Severely Deformed AA7075 Alloy

Microstructure and Mechanical Properties of Spark Plasma Sintered and Severely Deformed AA7075 Alloy

Historical Studies by Polish Scientist on Ultrafine-Grained Materials by Severe Plastic Deformation

Strength properties and structure of CuCrZr alloy subjected to low-temperature KOBO extrusion and heat treatment

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