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Author (up) van Dalen, Marsha E. pdf  openurl
  Title Microstructure and Creep Properties of Al-Sc Alloys Micro-alloyed with Lanthanides (Yb or Gd) and Transition Metals (Ti or Zr) Type Book Whole
  Year 2007 Publication Abbreviated Journal  
  Volume Issue Pages 289  
  Keywords Al-Sc  
  Abstract This thesis examines the effects of micro-alloying additions to Al-Sc alloys on the

microstructure, coarsening resistance and creep properties. The overarching goal of this research

is to develop castable, creep-resistant aluminum alloys which can be used at temperatures in

excess of 300°C. Successful high-temperature application of aluminum based alloys offers a

lower cost and lower weight alternative to other materials commonly used at high temperatures,

including titanium- and nickel-based alloys.

To this end, this aims to improve the properties of the Al alloys by adding various

alloying elements in small quantities, on the order of several hundred atomic parts per million, to

aluminum. The thesis begins by focusing on additions of Ti to Al-Sc. Ti is a slow diffuser in Al

[1], and it will be shown that it improves the coarsening kinetics of the precipitate phase at

300°C. Since these alloys are coarsening resistant, it is found that they can be aged and crept at

temperatures of up to 425°C. The properties displayed are similar to those of Al-Sc-Zr alloys

studied previously [2, 3].

The examination of Ti additions is followed by a study of the additions of lanthanide

elements. These elements are of interest since they are known to increase the lattice parameter of

the precipitate phase [4-8], which could potentially lead to improved creep resistance [9].

Initially, binary Al-Yb alloys are studied to obtain some fundamental knowledge of the behavior

of Yb in Al. Subsequent additions of Yb to Al-Sc result in improved creep resistance. A similar

improved creep resistance is observed for additions of Gd to Al-Sc.

Finally, this dissertation concludes with the study of Al-Sc-Yb-Zr alloys. Since the goal

of this research is to obtain a creep-resistant as well as coarsening resistant alloy, both a slow

diffusing element (Zr) and an element which improves the creep resistance (Yb) are added. The

quaternary alloys are found to maintain the creep resistance and coarsening resistance of the Al-

Sc-Yb and Al-Sc-Zr alloys, respectively, which points to opportunities for future research in this

  Corporate Author Northwestern University Thesis Ph.D. thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number NU @ karnesky @ Serial 9848  
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