Effect of Grain Microstructure on Precipitation Behavior and Properties of 2195 Al-Li Alloy under Stress-aging

Abstract:

In this paper, through tests such as constant stress creep tensile, room temperature tensile and slow strain rate tensile stress corrosion performance tests, combined with OM, SEM, TEM and EBSD microstructure observation and analysis to explore the effects of deformation and fine-grained two different grain structures on stress Effects of aging treatment on precipitation behavior and properties of 2195 Al-Li alloy. The results show that compared with the fine-grained sheet, the time for the deformed sheet to reach the peak hardness is shortened from 18h to 4h, the peak hardness is increased from 165.3HV to 228HV, and the tensile strength is increased from 584.6MPa to 641.9MPa. 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 ISSRT value of the deformed sheet was reduced from 7.6% to 4.8%, and the stress corrosion susceptibility was reduced. The proportion of large-angle grain boundaries of the deformed sheet is reduced 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. reason.

Key words:2195 aluminum-lithium alloy; stress aging; grain structure; stress corrosion resistance