Compressive deformation behavior and microstructure evolution of AA2099 Al–Li alloy containing Al3Li precipitates based on experimental characterization and crystal plasticity finite element simulation

Abstract

Deformation behavior of AA2099 Al–Li alloy containing Al3Li (δ′) precipitates at room temperature has been systematically investigated via uniaxial compression experiments, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) measurements as well as crystal plasticity finite element (CPFE) simulation. By applying an appropriate heat treatment, these nano-sized δ′ precipitates with the diameter of 10–20 nm are obtained in AA2099 Al–Li alloy and the corresponding area fraction is about 1.12%. Microstructure characterizations confirm that these pre-existing δ′ precipitates survive during plastic deformation, meanwhile they would contribute to the formation of tangled and dense dislocations in Al matrix. An ingenious strategy is then proposed and coupled into the CPFE modeling to take account of the effect of δ′ phase on deformation behavior, namely δ′ precipitates contribute to the activity of co-planner slip and they are adverse to the activity of co-directional slip. These predicted mechanical behavior and texture evolution agree well with those experimentally measured ones, which verifies the validity of the conducted CPFE simulation. Moreover, CPFE modeling successfully predicts the occurrence of large and inhomogeneous Von Mises stress and dislocation density distribution in the case with δ′ phase. Besides, the statistical analysis on the coefficient variant about equivalent plastic strain strongly illustrates that these pre-existing δ′ precipitates contribute to the inhomogeneous distribution of plastic strain during plastic deformation.