Experimental and computational creep characterization of Al–Mg solid-solution alloy through instrumented indentation

Carefully designed indentation creep experiments and detailed finite-element computations were carried out in order to establish a robust and systematic method to extract creep properties accurately during indentation creep tests. Samples made from an Al–5.3mol%Mg solid-solution alloy were tested at temperatures ranging from 573 to 773K. Finite-element simulations confirmed that, for a power-law creep material, the indentation creep strain field is indeed self-similar in a constant-load indentation creep test, except during short transient periods at the initial loading stage and when there is a deformation mechanism change. Self-similar indentation creep leads to a constitutive equation from which the power-law creep exponent n, the activation energy Qc for creep, the back or internal stress and so on can be evaluated robustly. The creep stress exponent n was found to change distinctively from 4.8 to 3.2 below a critical stress level, while this critical stress decreases rapidly with increasing temperature. The activation energy for creep in the stress range of n1⁄4 3.2 was evaluated to be 123 kJmol , close to the activation energy for mutual diffusion of this alloy, 130 kJmol . Experimental results suggest that, within the n1⁄4 3.2 regime, the creep is rate controlled by viscous glide of dislocations which drag solute atmosphere and the back or internal stress is proportional to the average applied stress. These results are in good agreement with those obtained from conventional uniaxial Philosophical Magazine ISSN 1478–6435 print/ISSN 1478–6443 online # 2003 Taylor & Francis Ltd http://www.tandf.co.uk/journals DOI: 10.1080/14786430310001616045 {Author for correspondence. Email: [email protected]. {Author for correspondence. Email: [email protected]. creep tests in the dislocation creep regime. It is thus confirmed that indentation creep tests of Al–5.3mol%Mg solid-solution alloy at temperatures ranging from 573 to 773K can be effectively used to extract material parameters equivalent to those obtained from conventional uniaxial creep tests in the dislocation creep regime. }