Analysis of flow stress and microstructure during hot compression of 6099 aluminum alloy (AA6099)

The hot deformation behavior of a newly developed AA6099 alloy was investigated after homogenization. To this end, Gleeble (R) isothermal hot compression tests were performed at temperatures of 350, 400, 450, and 500 degrees C, and strain rates of 0.01, 0.1, and 1 s(-1) up to a true strain of 0.8. The dependency of the flow stress on the deformation temperature, strain, and strain rate was analyzed. In addition, the constitutive equations relating the flow stress to the deformation temperature and strain rate were derived using a power-law empirical model. Also, the microstructures and dynamic softening mechanisms of the alloy under various deformation conditions were examined using light optical microscopy (LOM) and electron back scattered diffraction (EBSD) techniques. The correlation between the flow behavior, different microstructures, and dynamic softening mechanisms at various hot compression conditions was determined. The kinetic analysis and microstructural evolution indicated that the main flow softening mechanism for homogenized AA6099 was dynamic recovery (DRV). Partial dynamic recrystallization (DRX) enhanced the flow softening especially at low deformation temperatures and high strain rates, i.e., at high Zener-Hollomon parameter (Z) values.