Micro-CT defect analysis and hardness distribution of flat-face extruded EN AW6060 aluminum chips

Philipp Goerlich; Ronja Scholz; Frank Walther

doi:10.3139/120.111050

Article

Micro-CT defect analysis and hardness distribution of flat-face extruded EN AW6060 aluminum chips

Philipp Goerlich , Ronja Scholz and Frank Walther

Published/Copyright: July 10, 2017

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From the journal Materials Testing Volume 59 Issue 7-8

Abstract

Besides the energy-intensive secondary metallurgical recycling route, aluminum chips can alternatively be extruded to final profiles by extrusion. The mechanical properties of the extruded profiles have a dependency on the quality of the weldments of the chips, which differs locally due to the batch process. To characterize the influence of this dependency on the mechanical properties, round pre-compacted chip blocks consisting of EN AW-6060 were pre-heated for six hours at 550 °C, extruded with flat-face dies at a recipient temperature of 450 °C and divided into three zones: profile, transition and contact zone. A micro-computed tomographic defect analysis was performed on the samples. It has been shown that the profile samples of both geometries have a very low defect quantity and volume, while towards the contact zone the number and volume increases significantly and small delaminations occur on the surface. For the determination of the hardness distribution, a macro hardness mapping was performed. The coarse grain edge in the outer region of the specimens, which has resulted from increased temperature as a result of the recipient friction and shear stress, shows a slightly increased hardness. Round profiles show a concentric hardness decrease and square profiles a linear drop towards the center of the cross section of the specimens.

Kurzfassung

Neben der energieintensiven sekundärmetallurgischen Recyclingroute, können Aluminiumspäne alternativ mit einer Strangpressanlage zu finalen Profilen gepresst werden. Die mechanischen Eigenschaften der gepressten Profile weisen eine Abhängigkeit von der Qualität der Verschweißung der Späne auf, die sich im Batch-Prozess lokal unterscheidet. Zur Charakterisierung des Einflusses dieser Abhängigkeit auf die mechanischen Eigenschaften wurden runde vorkompaktierte Spanblöcke aus EN AW-6060 sechs Stunden bei 550 °C vorgeheizt, bei einer Rezipiententemperatur von 450 °C mit zwei unterschiedlichen Flachmatrizen gepresst und in je drei Zonen unterteilt: Profil, Übergang und Kontakt. An den Proben wurde eine mikro-computertomographische Defektanalyse durchgeführt. Die Profilproben beider Geometrien weisen eine sehr geringe Defektanzahl und -volumina auf, während zur Kontaktzone hin die Anzahl stark ansteigt und ebenfalls kleine Delaminationen auf der Oberfläche auftreten. Zur Ermittlung der Härteverteilung wurde ein Makro-Härtemapping durchgeführt. Der im äußeren Bereich der Proben entstandene Grobkornrand, der infolge einer erhöhten Temperatur durch Rezipientenreibung und Scherspannung entstanden ist, weist eine leicht erhöhte Härte auf. Runde Profile weisen dagegen eine konzentrische und quadratische Profile eine lineare Härteabnahme in Richtung Mittelpunkt des Probenquerschnitts auf.

*Correspondence Address, MSc Ronja Scholz, TU Dortmund University, Department of Materials Test Engineering (WPT), Baroper Str. 303, D-44227 Dortmund, Germany, E-mail: ronja.scholz@tu-dortmund.de

Philipp Goerlich, MSc RWTH Aachen University, born in 1989, studied Industrial Engineering with specialization in Materials and Process Engineering at RWTH Aachen University, Germany. After his master thesis, he has been working in the Department of Materials Test Engineering (WPT) at TU Dortmund University, Germany, since 2016. His research focus is on the determination and expansion of the application limits in the metal forming recycling of aluminum chips.

MSc Ronja Scholz, born in 1987, studied Sales Engineering and Product Management with specialization in Materials Engineering at Ruhr University Bochum, Germany. After her master thesis, she has been working as a scientific assistant in the Department of Materials Test Engineering (WPT) at TU Dortmund University, Germany, since 2014. Her research focus is on fatigue and fracture of resource-efficient composite materials.

Prof. Dr.-Ing. Frank Walther, born in 1970, studied Mechanical Engineering majoring in Materials Science and Engineering at TU Kaiserslautern University, Germany, from 1992 to 1997. There, he finished his PhD on the fatigue assessment of railway wheel steels in 2002, and his habilitation on physical measurement techniques for microstructural-based fatigue assessment and lifetime calculation of metals in 2007. At Schaeffler AG in Herzogenaurach, Germany, he took responsibility for Public Private Partnership within Corporate Development from 2008 to 2010. Since 2010, he has been Professor for Materials Test Engineering (WPT) at TU Dortmund University, Germany. His research portfolio includes determination of structure-property-relationships of metal- and polymer-based materials and components under fatigue loading from LCF to VHCF range, taking the influence of manufacturing and joining processes as well as service loading and corrosion deterioration into account.

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Published Online: 2017-07-10

Published in Print: 2017-07-14

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https://doi.org/10.3139/120.111050