Abstract
Given the complex process condition, extruded aluminum (Al) alloy tubes show locally pronounced differences in microstructure and mechanical properties, which can be influenced by subsequent heat treatment. In the present study, cyclic indentation tests (CITs) were conducted on extruded Al alloy EN AW-6082 to locally determine hardness and cyclic hardening potential, which was complemented with light optical microscopy. To analyze the influence of extrusion process and subsequent heat treatment, the EN AW-6082 tubes investigated were manufactured with extrusion ratios Ψ of 13:1 and 22:1, both in as-extruded and T6 heat-treated conditions. The results obtained for the as-extruded state showed significant differences of the local mechanical properties and demonstrated that an increased Ψ leads to higher hardness, caused by more pronounced plastic deformation during the manufacturing process. Moreover, an increase of hardness and cyclic hardening potential was observed after a T6 heat treatment, which also reduced the difference in hardness between the different extrusion ratios. Additionally, the pronounced local differences in hardness and cyclic hardening potential correlated with the local microstructure. The results demonstrated that CITs enable the analysis of local mechanical properties of extruded EN AW-6082 profiles, resulting from different extrusions ratios as well as subsequent heat treatment.
Highlights
Published: 30 April 2021The ongoing trend in the transportation industry to save weight by the downsizing of components increases the material requirements
Note that the vertical axis of Figure is shown in position of the ha,p-N curves can be associated with the cyclic plasticity of the material, reverse direction
Based on the data obtained, these property variations can be partially explained. For both the as-extruded and the T6 heat-treated states a fine-grained zone occurred in the area of the outer and inner surface, whereas the center of the wall was characterized by relatively large and elongated grains. This can be explained by dynamic recrystallization, which occurred during the extrusion process and took place at the inner and outer surface of the tube, where the process temperature was assumed to be maximal
Summary
Published: 30 April 2021The ongoing trend in the transportation industry to save weight by the downsizing of components increases the material requirements. A sound knowledge of the mechanical and especially cyclic properties of lightweight materials is a prerequisite and, of great industrial interest. This is underlined by broad applications of lightweight components made of aluminum (Al) alloys in the automotive and aerospace industry. In this context, thin-walled structures are used to improve crash resistance and safety while not increasing overall weight [2]. The potential of such structures for absorption of mechanical energy depends primarily on their shape, with cylindrical tubes absorbing the most energy per unit mass [3]
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