Low stress creep behaviour of 7075 high strength aluminium alloy

Creep behaviour of 7075 aluminium alloy has been investigated in the temperature range 350-410degreesC and at applied tensile stresses between 1.8 and 6.3 MPa. The as-received material was thermomechanically processed to obtain 48 mum grain size, with grain growth to 78 mum, during creep and a thixoforged sample was also investigated. A transition from a region of low stress exponent (approximate to1) to a higher stress exponent (approximate to,5) was observed on increasing the stress above 5 MPa. The measured creep rates at low stresses were normalised for grain growth and found to be within a factor of 2 of the rates expected from the Nabarro-Herring equation. The value of activation energy for creep was found to be close to 147 kJ/mol. The measured rates were found to conform to rates measured at constant strain rates and comparably low stresses for superplastic 7075 aluminium alloy with comparable microstructure. (C) 2004 Elsevier B.V. All rights reserved.