Study On Solid Solution Aging Behavior Of New Al-Li-Cu-Mg Alloy

Al-Li alloy material is a new type of aluminum alloy material at the present stage.Al-Li alloy has its excellent properties,such as high strength,light weight,good corrosion resistance and relatively low cost.Aluminum-lithium alloy has become an indispensable material in aerospace industry because of its excellent mechanical properties and low density.It can be predicted that Al-Cu-Li-Mg alloys will have great development and application space in the field of aerospace.However,Al-Li alloy has some defects that are difficult to solve,such as poor coordination of strength and toughness,serious anisotropy and so on.These defects restrict the application of Al-Li alloy in aerospace industry to a great extent.In order to better apply the aluminum-lithium alloy in the aerospace industry,starting with the aging system of Al-Li alloy,this study focuses on the effects of aging temperature and aging time on the microstructure and mechanical properties of Al-Li alloy.The experimental data are analyzed and the following conclusions are drawn:The effects of aging temperature and aging time on the microstructure and mechanical properties of Al-Li alloy were studied by means of metallographic microscope,scanning electron microscope and hardness.The results show that,the mechanical properties of the Al-Li alloy increase with the increase of the temperature at any time.The aging strength of Al-Li alloy is higher than that of solid solution state.The strengthening phases in Al-Li alloy are?'?Al₃Li?phase,T₁?Al₂CuLi?phase and?'?Al₂Cu?phase.A large amount of?'phase and a small amount of T₁ phase were precipitated at 150?.With the increase of the aging temperature,the main precipitates are T₁ phase and?'phase,and a small amount of?'phase.When the aging temperature increases to 180?,the phase of precipitation is mainly T₁,with only a small amount of the?'phase and the?'phase.With the increase of aging temperature,the phase of the precipitation is gradually changed from the metastable?'phase and?'phase to the T₁phase.With the prolongation of aging time,the hardness of Al-Li alloy increases at first and then decreases and then tends to be stable with the prolongation of aging time,and the toughness of Al-Li alloy increases gradually with the increase of aging time.The maximum tensile strength is 566.565 MPa and the maximum yield strength is 592.217MPa.The strain hardening index n also increases with the increase of the temperature.Judging by fracture surface,the fracture mechanism of Al-Li alloy is short transverse lamellar fracture along crystal.Under the same aging time,with the increase of aging time,the delamination phenomenon is more obvious,and the layer is more dense,and the number of dimples decreases gradually with the aging time.With the increase of aging temperature,the dimples on the tensile fracture surface of the specimen decrease gradually,and the transgranular fracture gradually changes to the phase intergranular fracture.