The Effect of Deformation by Torsion and Subsequent Heat Treatment on the Microstructure of AA6082

Abstract

An AA6082-aluminum alloy is used in the production of suspension components for cars at Raufoss Technology AS. The components are manufactured through a process of several forming and heating steps. Through torsion testing with subsequent heat treatment, it has been found that the alloy is susceptible to recrystallization during heat treatment following deformation. A linear relationship between the heat treatment temperature and Zener-Hollomon parameter Z and risk of recrystallization is proposed. This relationship suggests that there is a risk of a recrystallized microstructure after post-deformation heat treatment at temperatures above T_(heat treatment) [℃]=1355-30×ln⁡Z.

The flow properties of the material during hot working conditions were examined by torsion testing. Constitutive relations are suggested based on the recorded experimental stress-strain curves and strain rate and deformation temperature measurements. The activation energy for hot work is estimated to be Qhw = 170 kJ/mol for the alloy. The experimental data are found to deviate from the suggested constitutive relations at low deformation temperatures (T = 350℃ and T = 400℃) and shear strain rates below 1 s-1. The constitutive relations are generally found to correlate with the experimental data at higher strain rates and deformation temperatures.