Anisotropy And Corrosion Behavior Of 2060A Al-Li Alloy Thick Plate

2060A Al-Li alloy thick plate is the fourth generation of Al-Li alloy independently developed by China.The rolled al-Li alloy has obvious anisotropy.At the same time,due to the high sensitivity of Li element to corrosion,the corrosion resistance of Al-Li alloy decreases,which affects the wide application of 2060A Al-Li alloy in aerospace.Therefore,the anisotropy and corrosion properties of 2060A alloy need to be further studied.In this paper,the anisotropy and corrosion resistance of 2060A Al-Li alloy thick plate were studied by OM,SEM,EBSD,TEM,tensile mechanical property test at room temperature,polarization curve,intercrystalline corrosion and spallation corrosion test.The main results are as follows:（1）The fracture mode of 2060A Al-Li alloy thick plate at 0°and 30°directions is mainly plastic fracture,while the fracture mode at 45°and 90°directions is mainly intergranular and transgranular mixed fracture.In the thickness direction,the surface has obvious plastic fracture characteristics,and the 1/4 and 1/2 thickness layers are mainly intergranular fracture and transgranular fracture.The anisotropy of mechanical properties of the alloy is as follows:in plane direction,the strength is the highest in 0°direction and the lowest in 45°direction,but the elongation and area shrinkage are the highest,and the elongation and area shrinkage are the lowest in 90°direction.The yield strength and tensile strength of the 1/2 thickness layer are the highest,while the yield strength of the 1/4 thickness layer is the lowest,but the elongation and area shrinkage are the highest.Although the tensile properties of alloy with different direction and thickness are different,they all exceed the aviation standard.（2）The precipitates of 2060A Al-Li alloy thick plate are mainly T₁ phase,and a small amount ofθ’phase andδ’/β’composite phase.In the same plane,the number of precipitated phases in 0°direction is far more than that in other directions,and the precipitation ratio is small,and the strengthening effect is the most obvious,followed by the precipitation in 90°direction,and the number of precipitated phases in 30°and 45°direction is relatively small,and the strengthening effect is weakened.In the direction of thickness,the number of precipitated phase in the 1/2 thickness layer is the largest and evenly distributed,and the strengthening effect is the most obvious.The number of precipitated phase in the 1/4thickness layer is less than that in the 1/2 thickness layer,and the size of precipitated phase is larger,and the strengthening effect is the second.The number of precipitated phase on the surface is the least and the distribution is not uniform,and the strengthening effect is the worst.（3）In the same plane of 2060A Al-Li alloy thick plate,the texture strength of 45°direction is the highest,and there is a strong recrystallization texture P{011}<122>,the texture strength of 0°direction is higher,there is a strong deformation texture Copper{112}<111>,and the texture strength of 30°and 90°direction is relatively weak.In the direction of thickness,the texture strength of the surface is the highest,with a strong recrystallized brass texture{236}<385>,followed by the 1/4 thickness layer,which is mainly composed of deformation texture Copper{112}<111>and deformation texture S{123}<634>.The texture strength of the 1/2 thickness layer is relatively weak.The recrystallization texture P{011}<122>is dominant.（4）In the same plane,the average intercrystalline corrosion depth and spalling corrosion rate of 2060A Al-Li alloy thick plate in the direction of 0°and 45°are greater than those in the direction of 30°and 90°,and the corrosion resistance is poor,and with the increase of corrosion time,the spalling corrosion rate becomes faster and faster.After 96 h of peeling corrosion,the corrosion grade of the three layers is EA,but the corrosion rate and the average intergranular corrosion depth of the surface are far greater than that of the 1/4 and 1/2 layers,that is,the corrosion resistance of the surface is worse than that of the 1/4 and 1/2 layers,which is consistent with the polarization curve results of the thickness direction.At the same time,the peeling corrosion properties of different direction and thickness of the alloy conform to the national standard of aluminum alloy peeling corrosion.