Microstructure Evolution During High-Temperature Deformation of 8090 Al-Li Alloy

Abstract

The microstructure evolution of an as-processed 8090 Al-Li alloy during high temperature deformation has been investigated with emphasis on the dynamic grain size refinement and the formation of high-angle grain boundaries. Tensile tests were conducted at temperatures 470–560°C and initial strain rates of 10⁻²–10⁻⁶ s⁻¹. The starting and deformed samples were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Electron Backscattered Diffraction (EBSD). The material showed a maximum elongation to failure of 660% at 530°C and strain rate of 10⁻³ s⁻¹. A microstructural transformation from coarse grains to uniform fine microstructure through dynamic recrystallization (DRX) was observed. The DRX process was characterized by (1) a bimodal microstructure, (2) a gradual increase in average boundary misorientation angles, and (3) a gradual decrease of microtexture. The development of high angle boundaries was attributed to the absorption of dislocations into subboundaries and the grain boundary sliding (GBS)-induced subgrain rotation. The microstructural evolution was suggested to be responsible for the superplastic behavior observed in this as-processed material.

Keywords:

• Al-Li alloy
• Superplasticity
• Boundary character
• Dynamic recrystallization
• Elongation to failure
• Electron backscattered diffraction
• Microstructure
• Misorientations
• Grain boundary sliding
• Dislocation
• Thermomechanical processing
• Microtexture
• Facture
• Mechanical property
• Orientation imaging microscopy