Characterization of plastic instability steps occurring in depth-sensing indentation tests

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Plastic instabilities in solid solution Al-Mg and supersaturated A1-Zn-Mg-(Cu) alloys were investigated by depth-sensing microhardness tests. Experimental results show that in the case of A1-Mg alloys the characteristics of the plastic instability depend only on the solute concentration. In the case of age-hardenable A1-Zn-Mg-(Cu) alloys, however, although plastic instabilities were observed during indentation following the quenching, the development of the instability steps is strongly influenced by Guinier-Preston zone formation in the early stage of natural aging. After a certain time, ti, of aging the steps disappear completely. The value of ti obtained for the Cu-containing alloy was found to be considerably longer than that obtained for the ternary A1-Zn-Mg alloy. This fact - together with the smaller initial rate of hardening in the Cu-containing alloy - indicates that the addition of Cu retards the early part of the decomposition process at room temperature in this alloy system.

Original languageEnglish
Pages (from-to)219-224
Number of pages6
JournalMaterials Science and Engineering A
Issue number1-2
Publication statusPublished - Feb 15 2002



  • Al-Zn-Mg and Al-Zn-Mg-Cu alloys
  • Depth-sensing indentation
  • Guinier-Preston zones
  • Plastic instabilities

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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