Dynamic recrystallisation and dynamic precipitation in AA6061 aluminium alloy during hot deformation

Abstract

Deformation behaviour of AA6061 alloy was investigated using uniaxial compression tests at temperatures from 400 to 500°C and strain rates from 0·01 to 1 s⁻¹. Stress increases to a peak value, then decreases monotonically until reaching a steady state. The dependence of stress on temperature and strain rate was fitted to a sinh-Arrhenius equation and characterised by the Zener–Hollomon parameter with apparent activation energy of 208·3 kJ mol⁻¹. Grain orientation spread analysis by electron backscattered diffraction indicated dynamic recovery and geometrical dynamic recrystallisation during hot compression. Deformation at a faster strain rate at a given temperature led to finer subgrains, resulting in higher strength. Dynamic precipitation took place concurrently and was strongly dependent on temperature. Precipitation of Q phase was found in the sample deformed at 400°C but none at 500°C. A larger volume fraction of precipitates was observed when samples were compressed at 400°C than at 500°C.

Keywords:

• Aluminium
• Flow stress
• Dynamic recovery
• Geometric dynamic recrystallisation
• Dynamic precipitation

Acknowledgements

The authors appreciate the University Research Program supported by Ford Motor Company. The authors also extend their thanks to W. T. Donlon and K. Sun for their valuable discussion related to TEM samples preparation and analysis. The authors also would like to acknowledge the support of Major Projects of the Ministry of Education (Grant Nos. 311017, 20120073130010), National Key Technology R&D Program (Grant No. 2012BAF01B06) and the program of Introducing Talents of Discipline to Universities (Grant No. B06012).