Einfluss von Legierungselementen auf das Eigenschaftsprofil von Aluminium-Knetlegierungen der 7xxx-Serie

Translated title of the contribution: Influence of alloying elements on the properties of aluminum wrought alloys (7xxx-series)

Stefanie Scheiber

Research output: ThesisMaster's Thesis

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Abstract

Due to political regulations CO2-emissions need to be decreased, especially in automotive and aviation industry. Therefore, new alloys are tested for lightweight design. These construction materials have to fulfil a number of mechanical and chemical properties. Certain established material properties must be reached under static and dynamic conditions. The present master thesis comprises melting, alloying and casting of the aluminium alloy EN AW-7075 according to standard DIN EN 573-3. A variation of elements (Mg and Zn) within the standard is obtained. The chemical composition of materials is measured by the use of optical emission spectroscopy (OES). Sawing and cutting enable the preparation of specimen in the right quantity and shape. Thermal analysis, especially differential scanning calorimetry (DSC), showed the specific melting points of alloys. The determined values deliver information about required and limiting temperatures during homogenisation treatment. Moreover, the results are compared to thermodynamic calculations using the software FactSage™ 6.4. The microstructure of materials in as-cast and homogenised condition is examined by optical microscopy. The images are used for determination of average grain size. The intercept method according to ASTM E112 was applied in grinded, polished and etched specimen. The mechanical properties like hardness, yield strength and ultimate tensile strength as well as elongation to fracture were tested. For this purpose, the alloys were hot forged, solution treated and quenched prior to sample cutting. In addition, the tensile specimen were artificial aged to T6 condition. While strength was in the range of expected values, the elongation was lower than the values described in literature. The hardness was tested at different times for natural and artificial aging. While natural aging at room temperature did not increase hardness very much, the maximum values were obtained after 20 h at 125 °C. The results are presented in time versus hardness diagrams.
Translated title of the contributionInfluence of alloying elements on the properties of aluminum wrought alloys (7xxx-series)
Original languageGerman
QualificationDipl.-Ing.
Supervisors/Advisors
  • Antrekowitsch, Helmut, Supervisor (internal)
  • Pogatscher, Stefan, Co-Supervisor (internal)
  • Kolb, Gernot, Co-Supervisor (internal)
Award date30 Oct 2015
Publication statusPublished - 2015

Bibliographical note

embargoed until 21-10-2020

Keywords

  • 7075
  • AlZnMgCu
  • 7xxx
  • mechanical properties
  • hardness
  • DSC
  • FactSage
  • microstructure

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