Dislocation density model and microstructure of 7A85 aluminum alloy during thermal deformation

Abstract

The microstructure evolution of 7A85 aluminum alloy at the conditions of strain rate (0.001 − 1 s⁻¹) and deformation temperature (250–450 °C) was studied by optical microscopy (OM) and electron back scattering diffraction (EBSD). Based on the K-M dislocation density model, a two-stage K-M dislocation density model of 7A85 aluminum alloy was established. The results reveal that dynamic recovery (DRV) and dynamic recrystallization (DRX) are the main mechanisms of microstructure evolution during thermal deformation of 7A85 aluminum alloy. 350–400 °C is the transformation zone from dynamic recovery to dynamic recrystallization. At low temperature (≼350 °C), DRV is the main mechanism, while DRX mostly occurs at high temperature (≽400 °C). At this point, the sensitivity of microstructure evolution to temperature is relatively high. As the temperature increased, the average misorientation angle (

{\overline{\theta }}_{\text{c}}

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) increased significantly, ranging from 0.93° to 7.13°. Meanwhile, the f_LAGBs decreased with the highest decrease of 24%.

Keywords

hot deformation / microstructure evolution / dynamic recrystallization / dislocation density model

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