The Effect Of Alloy State And T₁（Al₂CuLi） Phase On Localized Corrosion Behavior Of AA 2099 Al-Li Alloy

T₁（Al₂CuLi）phase is the main strengthening phase of AA 2099 Al-Li alloy.However,due to the chemical properties of Li（lithium）elements lively,T₁phase in the wet,salt spray and other harsh environments tends to corrosion,and significantly affects the corrosion resistance of Al-Li alloy.In this paper,AA 2099 Al-Li alloy was used as the research object.The corrosion behavior of AA 2099 Al-Li alloy was studied by the methods of immersion,potentiodynamic polarization and galvanic corrosion experiments.The electrochemical behavior of the alloy was studied by SEM,EBSD and TEM.Impact.The main conclusions are as follows:（1）The original structure of extruded AA 2099 Al-Li alloy has a strong preference orientation,and grain along the extrusion direction was fibrous distribution.After heat treatment and recrystallization annealing treatment,there forms a certain number of equiaxed recrystallization grains on the sample surface,and the sample heart is still the original fibrous tissue.（2）Potentiodynamic polarization experiments are carried out to determine the corrosion potential of as-cast AA 2099 Al-Li alloy in four heat treatment states,solid solution,homogenization,T6 and T8 state.The corrosion potentials are-0.582V、-0.676V、-0.699V、-0.724V,respectively.The internal precipitates of the homog-enized sample are mainly coarsened T₁ phase,and after the potentiodynamic polariz-ation experiment,the corrosion path is extended along the T₁ phase.（3）In the 3.5 wt.%NaCl solution,the Li and Al elements in the T₁ phase are selectively dissolved,and the Cu nanoparticles are enriched simultaneously.The enriched Cu element changes the polarity of the T₁ phase which becomes the cathode of the corrosion battery and leads Al matrix anode to dissolve.Corrosion morphology has become coffee bean-like ultimately.（4）The localized corrosion of the as-cast AA 2099 Al-Li alloy sample in the 3.5wt.%NaCl solution is related to the grain orientation.The corrosion tendency of the crystal surface exposed to the solution is from large to small,（100）plane,near（110）plane and near（111）plane.（5）Galvanic corrosion experiments show that the corrosion tendency of homogenization sample,T8 sample and T6 sample in 3.5 wt.%NaCl solution increases in turn,indicating that the heterogeneity of T₁ phase distribution has a great influence on the corrosion behavior of Al-Li alloy,and the size of T₁ phase has little effect on the corrosion behavior of Al-Li alloy.