Kinetic model for describing continuous and discontinuous dynamic recrystallization behaviors of 2195 aluminum alloy during hot deformation

Abstract

2195 aluminum alloy is widely used to manufacture the external tanks of space shuttles and aircraft skins, and its mechanical properties are substantially affected by dynamic recrystallization occurring in its microstructure. In this study, hot compression experiments were performed on 2195 aluminum alloy to investigate its dynamic recrystallization (DRX) behavior. The results indicated that discontinuous (DDRX) and continuous dynamic recrystallization (CDRX) both occurred in the alloy from 300 °C to 520 °C at strain rates of 0.01–10 s −1 . The microstructure analysis revealed that DDRX grains formed at grain boundaries, while CDRX grains appeared in the triangular grain boundary region with transition grain boundaries or within grains. The dominant DRX mechanism changed from DDRX to CDRX when the strain was greater than 1.2. Moreover, at higher temperatures or lower strain rates, the number of CDRX grains increased, while the number of DDRX grains decreased. Finally, to quantitatively describe the DDRX and CDRX kinetics of 2195 aluminum alloy, the critical conditions were used to establish a composite kinetics model that was consistent with the experimental results, and which suitably predicted the volume fraction of DRX grains formed via the two different DRX mechanisms. • A strain of 1.2 was the transition point between the two recrystallization mechanisms for 2195 aluminum alloy under thermal compression. • Upon increasing the temperature or decreasing the strain rate, CDRX grains increased, while DDRX grains decreased. • Critical conditions of dynamic recrystallization were found and the critical stress, critical strain and other stress of model were established. • A composite kinetics model was proposed by considering the characteristics of DDRX and CDRX.