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Analysis of the influence of dies geometry on the process extrusion force and properties of the extrudate obtained in the process of cold extrusion of 7075 aluminum alloy by the KOBO method Cover

Analysis of the influence of dies geometry on the process extrusion force and properties of the extrudate obtained in the process of cold extrusion of 7075 aluminum alloy by the KOBO method

Materials Science-Poland
Volume 42 (2024): Issue 1 (March 2024)
By: Marek Zwolak and  Romana Śliwa  
Open Access
|May 2024

Figures & Tables

Fig. 1.

Schematic of KOBO extrusion process: 1- container sleeve, 2- butt, 3- die, 4- billet

Fig. 2.

2500 kN KOBO extrusion press

Fig. 3.

Macrostructure of the longitudinal section of the test material in the initial state (annealed 7075 aluminum alloy)

Fig. 4.

Microstructures of 7075 aluminum alloy initial condition, cross-section (a) and longitudinal section (b), 500x mag

Fig. 5.

Sketch of characteristic features of dies for KOBO process

Fig. 6.

Dies used for experimental research

Fig. 7.

Graph of the extrusion force as a function of stem displacement

Fig. 8.

Graph of stress-strain relationships in static tensile test of extruded products – samples taken from three areas along the length of the extrudate – series 1

Fig. 9.

Graph of stress-strain relationships in static tensile test of extruded products – samples taken from three areas along the length of the extrudate – series 2

Fig. 10.

Graph of stress-strain relationships in static tensile test of extruded products – samples taken from three areas along the length of the extrudate – series 3

Fig. 11.

Macrostructure of 7075 alloy: front, 200x mag.; middle, 100x mag.; and end extrusion stages, 100x mag. Visible shear lines in the near-surface area

Fig. 12.

Macrostructure of alloy 7075 after conventional extrusion: front, middle and end extrusion stages, 100x mag. No clear shear lines, visible peripheral disruption of the alloy microstructure due to flow

Fig. 13.

Microstructure of 7075 alloy: cross-sectional view of the near-surface area (a) and the area inside the bar (b), and longitudinal section of the near-surface area (c) and the area inside the bar (d), 500x mag

Fig. 14.

Microstructure of 7075 alloy typical of all tested KOBO samples in the near-surface zone (a and c, 200x mag.) and beyond (b and d, 1000x mag.). Longitudinal section, SEM

Fig. 15.

Microstructure of 7075 alloy, test NG (F): cross-section of the near-surface area (a) and the area inside the bar (b) and longitudinal cross-section of the near-surface area (c) and the area inside the bar (d), 500x mag

Fig. 16.

Microstructure of the extrudate, sample NG (F): longitudinal cross-section, visible inhomogeneity due to the banded structure of the rod, SEM, (a) 1000x mag., (b) & (c) 3000x mag

Mechanical properties of extrudate determined by static tensile test – series 1

Rp0.2RmA50
MPaMPa%
G8D1F194.3767319.76316.82835
G8D1M182.0377325.006915.53416
G8D1E191.4832351.631117.21147
G8D2F191.682329.369416.09939
G8D2M184.0032325.381117.21048
G8D2E174.6589327.050614.48359
G8D3F191.8396326.37118.55923
G8D3M179.7999322.988517.81401
G8D3E187.1591344.830914.46475

Mechanical properties of extrudate determined by static tensile test – series 2

Rp0.2RmA50
MPaMPa%
G6D1F139.9892375.777218.3135
G6D1M203.2703351.691115.75259
G6D1E203.6512357.123815.73096
G10D1F219.1892359.816517.40554
G10D1M213.132362.429217.7133
G10D1E211.7307372.726515.55199
G12D1F228.0526372.501416.29631
G12D1M204.0853361.952217.48726
G12D1E217.7237377.166313.81927

Mechanical properties of extrudate determined by static tensile test – series 3

Rp0.2RmA50
NG_KOBO F227.5532363.612711.61306
NG_KOBO M210.6277368.383737.3797
NG_KOBO E194.2238354.839916.83634
NG F178.6093314.830212.87594
NG M178.4273318.896927.68791
NG E179.8115303.12399.513819

Dimensions of the characteristic features of the dies used for experimental research

CodeNumber of groovesGrooves depth [mm]
G8D181
G8D282
G8D383
G6D161
G10D1101
G12D1121
NG––

Maximum recorded extrusion forces in the KOBO process using different die types

TestMaximum extrusion force [kN]Comment
G8D12086No container sleeve cleaning before test
G8D21962
G8D31962
G6D11924
G10D11906
G12D11890
NG KOBO1923Flat face die
NG1458Conventional extrusion at 450° C
Butt79Butt pushing force while cleaning container sleeve
DOI: https://doi.org/10.2478/msp-2024-0008 | Journal eISSN: 2083-134X | Journal ISSN: 2083-1331
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Language: English
Page range: 92 - 106
Submitted on: Dec 29, 2023
|
Accepted on: Apr 24, 2024
|
Published on: May 22, 2024
Published by: Wroclaw University of Science and Technology
In partnership with: Paradigm Publishing Services
Publication frequency: 4 issues per year
Keywords:
aluminum extrusion,
KOBO method,
7075 aluminum,
bulk forming
Related subjects:
Materials sciences,
Materials sciences, other,
Nanomaterials,
Functional and smart materials,
Materials characterization and properties

© 2024 Marek Zwolak, Romana Śliwa, published by Wroclaw University of Science and Technology
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

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