Low stress creep behaviour of 7075 high strength aluminium alloy

Creep behaviour of 7075 aluminium alloy has been investigated in the temperature range 350–410 °C and at applied tensile stresses between 1.8 and 6.3 MPa. The as-received material was thermomechanically processed to obtain 48 μm grain size, with grain growth to 78 μm during creep and a thixoforged sample was also investigated. A transition from a region of low stress exponent (≈1) to a higher stress exponent (≈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.