Effect of Grain Microstructure on Precipitation Behavior and Properties of 2195 Al-Li Alloy Under Stress-Aging

The effects of two different grain structures i.e. deformation and fine-grain microstructure, on precipitation behavior and properties of 2195 Al-Li alloy were analyzed by constant stress creep tensile test, room temperature tensile test and slow strain rate tensile stress corrosion test combined with OM, SEM, TEM and EBSD. The results show that compared with the fine-grained sheet, the time for the deformed sheet to reach the peak hardness is shortened from 18 h to 4 h, the peak hardness increases from 1619.94 MPa to 2234.4 MPa, and the tensile strength increases from 584.6 MPa to 641.9 MPa. By calculating the contribution values of grain refinement strengthening, dislocation strengthening and precipitation strengthening to the improvement of alloy strength, it is found that the improvement of mechanical properties of deformed sheet is mainly due to the contribution of dislocation strengthening. At the same time, compared with the fine-grained sheet, the I-SSRT value of the deformed sheet reduces from 7.6% to 4.8%, and the stress corrosion susceptibility reduces. The proportion of large-angle grain boundaries of the deformed sheet reduces from 64.6% to 41.1% of the fine-grained sheet, the grain boundary precipitation phase distribution is more discrete, and the precipitation-free zone is hardly observed, which is the main reason for obtaining relatively excellent stress corrosion resistance.