Most commercial aluminum alloys are characterized by dynamic recrystallization at very large deformations in a continuous manner. The present study deals with the characterization and modeling of the evolution of the microstructure of an aluminum wrought alloy at large plastic deformations. Hot torsion tests of the AA6082 aluminum alloy are carried out using the thermomechanical simulator Gleeble®3800 in a wide range of temperatures and strain rates. The use of water quenching immediately after deformation avoids any static restoration during cooling. Microstructural investigations are carried out by means of electron back scattered diffraction using a scanning electron microscope to determine the grain and subgrain structures, as well as the misorientation distributions. In-situ synchrotron radiation tests during hot torsion are used to confirm the continuous dynamic recrystallization (CDRX) by the evidence of the conversion of low angle boundaries (LAGBs) into high-angle boundaries (HAGBs) and the formation of new texture. Experimental investigations show that CDRX starts with the formation of LAGBs at low strains (center of the sample). By subsequent straining (close to the surface of the sample), the accumulation of dislocations at the LAGBs causes an increase in their misorientation until a critical value is reached and LAGBs transforms into HAGBs. The developed model consists of a microstructural model, equation rates and constitutive equations. The microstructure is described by three internal variables. Their rates are evaluated using the Kocks-Mecking model. The modelled and experimental flow stresses show softening due to the consumption of dislocations and the continuous formation of new HAGBs.

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Gamma titanium aluminides are innovative materials for high temperature and light weight applications [1]. On the other hand, their hot workability can be limited by failure during hot deformation processes. The prediction of ductile damage in metallic materials can be performed by macromechanical ductile damage criteria [2-4]. If the calculated damage D parameter exceeds a critical value Dc, the material fails. Some macromechanical ductile damage criteria are shown in Table 1, with σ as effective stress, ε as effective strain, σmax as maximum principal stress, σm as hydrostatic stress (mean stress) and εf as equivalent fracture strain. The damage responds to strain localization and thus, to multiaxial stress concentration that increases fracture probability.

Titanium-based alloys are commonly applied to aerospace, medicine and energy due mainly to their high specific mechanical properties and high corrosion resistance. Reinforcement with particles further improves their specific strength and stiffness. In previous studies, the hot formability of both unreinforced Ti6Al6V2Sn alloy, and reinforced with 12%vol of TiC particles was analyzed by hot compression tests carried out by means of Gleeble device and metallography. It was observed that the hot workability of these materials is limited at given forming conditions by non-desirable shear bands, voids, as well as micro- and macro cracks, especially in the composite. In this work, damage during hot deformation is predicted by damage models coupled to FEM. Therefore, the flow localization parameter α described by thermal and microstructural softening and the strain rate sensitivity are computed and implemented in DEFORMTM 2D to describe the localization of the plastic flow. The results show intense flow localization as a combination of low dynamic restoration (given by small m values) and temperature gradient. The damage analysis combined with the Cockcroft and Latham continuum cumulative stress model.