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The large temperature gradient resulted from rapid heat dissipation and a long process period in the hot deformation of aluminum alloy causes complex microstructure evolutions. Accurate constitutive models describing the evolution of the microstructures over a wide temperature range are acquired. Thus, a physically-based continuous dynamic recrystallization constitutive model combined with grain fragmentation and subgrain rotation was established in this investigation. Uniaxial hot compression tests for aluminum alloy 2219 were conducted at temperatures of 250 °C–450 °C and the evolution of microstructures were analyzed via metallographic technique. Then internal state variables were proposed to describe the migration of grain boundary, dislocation density, average grain boundary misorientation, and subgrain/grain size. The net torque on the grain is introduced to precisely describe the progressive subgrain rotation mechanism. Moreover, geometrically necessary dislocations are considered to reasonably simulate the rise in flow stress associated with grain fragmentation. The results show that continuous dynamic recrystallization (CDRX) and dynamic recovery are the main softening mechanisms. The CDRX mechanism is gradually changed from grain fragmentation to subgrain rotation due to the increase in temperature. The new constitutive model may precisely predict the flow stresses, subgrain/grain size, and average misorientation in the wide temperature range. Comparing with the existing continuous dynamic recrystallization model which only considers subgrain rotation, the overestimate of the grain size in the low-temperature range is avoided in the new constitutive model. Furthermore, the contributions of the grain fragmentation to the increase in strain hardening can reasonably be covered.

Abstract. Bezier curve has been widely used as the roller path in conventional spinning. In this paper, Finite Element model with parameterized 2-pass conventional spinning tool paths based on quadratic Bezier curve is developed to explore the influence on the wall thickness reduction of spherical components. The results show that the first path has significant effect on wall thickness distribution and the selection of parameter values in tool path is crucial for thickness distribution.

Exploring the hot deformation behaviors of materials is essential for the precise numerical simulation of hot forming processes. In this study, the hot tensile deformation behaviors of aluminum alloy 2219-O are studied by uniaxial tensile tests at the temperature range of 473-673K and stain rate range of 0.001-0.1s -1 . Mechanism-based unified constitutive equations are developed to model the grain size, recovery and dislocation density. The results show that under the tested deformation conditions, the flow stress decreases with the increase of deformation temperature or the decrease of strain rate. Additionally, the increasing of elongations to fracture in this study indicates that the elevated temperature can improve the plasticity of AA2219-O. Moreover, the flow stresses predicted by the developed unified constitutive model well agree with the experimental data, which indicate that the developed constitutive model is valid.