The influence of the thermomechanical processing and forming parameters on superplastic behaviour of the 7475 aluminium alloy

Aluminium AA7475 alloy (Al-Zn-Mg-Cu) was thermomechanically treated by four procedures which included various combinations of rolling, solution annealing, quenching and overageing. The influence of these treatment procedures on the size and the stability of crystal grains and on superplastic properties of the alloy, such as the highest elongation without localised neck, strain rate sensitivity values, and flow stresses were determined. The highest elongations were over 1000%. With simplified thermomechanical treatment without separate solution annealing and overageing, a sheet with elongations up to 590% was made in industrial conditions. Influences of the parameters of superplastic forming (working temperature, strain rate) on superplastic properties of the alloy were determined too. (C) 2001 Published by Elsevier Science B.V.