Effects of T1/T2 precipitates on deformation behavior and microstructure evolution of AA2099 Al–Li alloy: experimental investigation and crystal plasticity finite element modeling

In the present study, effects of T1/T2 precipitates on microstructure characteristics and texture evolution of various AA2099 Al–Li alloy (AA2099-A and AA2099-B) samples are systematically investigated by conducting uniaxial compression experiments at room temperature, followed by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) measurements as well as crystal plasticity finite element (CPFE) simulation. The heat treatment for AA2099-A sample consists of solution treatment at 540 °C/1 h and artificial aging at 250 °C/1 h followed by water quenching, while the heat treatment for AA2099-B sample includes solution treatment at 540 °C/1 h and artificial aging at 250 °C/24 h followed by water quenching. Experimental results demonstrate that although dynamic recovery (DRV) serves as the major restoration mechanism for both samples, AA2099-A sample with T1 phase possesses obviously higher mechanical response by comparison with AA2099-B sample with T1/T2 phase. This observation shows a strong precipitate hardening effect derived from these dense and large-sized T1 precipitates in AA2099-A sample. Numerical results based on CPFE simulation demonstrate the occurrence of inhomogeneous plastic strain within the constructed grain-based representative volume element (RVE) model during uniaxial compression. Further statistical analysis on the coefficient variant about equivalent plastic strain verifies this issue and demonstrates that plastic strain distributes more homogeneously in AA2099-A sample than in AA2099-B sample. These dense and large-sized T1 precipitates are responsible for this phenomenon and they result in the fast rotation of grain orientation from <111>//ED to <110>//ED during uniaxial compression.