Optimierung von Aluminium-Knetlegierungen der 7xxx-Serie

Translated title of the contribution: Optimization of aluminium wrought alloys of the 7xxx series

Gernot Kolb

Research output: ThesisDoctoral Thesis

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Abstract

Constantly increasing requirements for an improvement of product properties and a sustainable production constantly demand innovations and developments from the aluminum industry to reduce the costs and energy expenditure for the production. In particular, the heat treatment of aluminium wrought alloys of the AlZnMg (Cu) series (7xxx) is a time-, energy- and cost-intensive process due to the necessary complex heat treatment process. In order to remain competitive, both the alloys in their constitution and the heat treatments, which make the use of the alloys possible, need to be optimized. Conventionally, to achieve the required demands on the mechanical properties of 7xxx alloys, the material is annealed after forming, rapidly quenched, stretched, and finally artificially aged. From the literature two fundamentally important material properties are known to be of importance: strength and toughness. Since the service life of components in aviation is defined by crack propagation and fatigue, high toughness is required, the weight of the vehicles (aircraft, helicopters, etc.) need to be as low as possible and therefore the strength should be as high as possible. These are two characteristics that must be linked together. To a certain extent, this is possible through the standard heat treatment in 7xxx alloys. In this work, the heat treatment concept of interrupted quenching (I.Q.) and its effect on the mechanical properties of aircraft plates in the 7xxx alloy system was studied. On the other hand, five new alloys based on literature and patents combined with thermodynamic CALPHAD tools based on the alloy EN-AW-7050 were created. Thermal analyzes were used to determine the phase transition behavior. Moreover, these results were compared with calculated phase diagrams generated by FactSage®, MatCalc and Pandat™. The obtained data were used to adjust the necessary and limiting temperatures during homogenization for the purpose of uniform element distribution. For the assessment of structural properties, differential calorimetry as well as light- and electron microscopy methods were used. The effect of different contents of alloying elements and the homogenization treatment was reveald.
Translated title of the contributionOptimization of aluminium wrought alloys of the 7xxx series
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
  • Pogatscher, Stefan, Co-Supervisor (internal)
  • Antrekowitsch, Helmut, Assessor A (internal)
  • Uggowitzer, Peter, Assessor B (external)
Publication statusPublished - 2017

Bibliographical note

no embargo

Keywords

  • 7xxx
  • Al-Zn-Mg-Cu
  • Interrupted Quenching
  • I.Q.
  • alloy design
  • CALPHAD
  • Differential Scanning Calorimetry
  • DSC

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