Dynamic Softening Mechanisms in Hot Processing Map of 1460 Al-Li Alloy

Abstract

Hot processing maps have been widely used to reveal the relationship between microstructures and final performances of Al-Li alloys after hot deformation as their extensiveness of application is greatly limited by the unstable properties. However, there are few researches on the hot processing maps of 1460 Al-Li alloy. In this paper, each safe zone was identified based on the corrected data with a temperature range of 300 - 500℃ and a strain rate range of 0.001 - 10 s -1 . Then, the microstructural characteristics and corresponding dynamic softening mechanisms were investigated by employing different characterization methods. The optimum domains were established at 300 - 500℃ / 0.001 - 0.01 s -1 dominated by continuous dynamic recrystallization (CDRX) and dynamic recovery (DRV), while cracks were obtained when temperature set around 450℃ with the highest power dissipation efficiency value of 55% approximately. Flow localizations and micro-shear bands are found in the instable domain of low temperature (< 400℃) and low strain rates (< 0.1 s -1 ) with lower power dissipation efficiencies (< 10%), then disappear as temperature increases and strain rate decreases. T 1 precipitate bands are developed in micro-shear bands inside the grains and provide pinning pressure on the dislocation movement. Besides, geometric dynamic recrystallization (GDRX) occurs at the domain of 500℃ / 10 s -1 , which attributes to the interaction of deforming forces and serrated grain boundaries. These findings can better optimize the hot work parameters of this alloy and expand its application field.

Keywords: 1460 Al-Li alloy, Hot processing map, Dynamic softening mechanism, microstructure