Effects of quench rate and natural ageing on the age hardening behaviour of aluminium alloy AA6060

Katharina Strobel, Matthew D.H. Lay, Mark A. Easton, Lisa Sweet, Suming Zhu, Nick C. Parson, Anita J. Hill

Research output: Contribution to journalArticleResearchpeer-review

21 Citations (Scopus)

Abstract

Quench sensitivity in Al-Mg-Si alloys has been largely attributed to the solute loss at the heterogeneous nucleation sites, primarily dispersoids, during slow cooling after extrusion. As such, the number density of dispersoids, the solute type and concentration are considered to be the key variables for the quench sensitivity. In this study, quench sensitivity and the influence of natural ageing in a lean Al-Mg-Si alloy, AA6060, which contains few dispersoids, have been investigated by hardness measurement, thermal analysis, transmission electron microscopy (TEM) and positron annihilation lifetime spectroscopy (PALS). It is shown that the quench sensitivity in this alloy is associated with the degree of supersaturation of vacancies after cooling. Due to vacancy annihilation and clustering during natural ageing, the quench sensitivity is more pronounced after a short natural ageing time (30 min) compared to a longer natural ageing time (24 h). Therefore, prolonged natural ageing not only leads to an increase in hardness, but can also have a positive effect on the quench sensitivity of lean Al-Mg-Si alloys.

Original languageEnglish
Pages (from-to)43-52
Number of pages10
JournalMaterials Characterization
Volume111
DOIs
Publication statusPublished - 1 Jan 2016

Keywords

  • Aluminium alloys
  • Natural ageing
  • Quench sensitivity
  • Vacancies

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