Abstract: Room temperature tensile properties, thermal stability, fracture morphology and microstructure of a new-type high strength and toughness Al-Li alloy thick plate under artificial aging condition were studied by means of tensile test, thermal stabilization test, scanning electron microscope(SEM) and transmission electron microscope(TEM).The results show that the tensile strength, yield strength and elongation of the alloy plate at T/2 thickness are higher than those at T/4 thickness at room temperature. This is because the deformation at T/2 thickness is larger and the dislocation density is higher, and more strengthening phase is precipitated during subsequent aging treatment. When the stabilization time is constant, the strength of the alloy increases at first with the increase of stabilization temperature. While the stabilizing temperature exceeds 150 ℃, the strength decreases significantly, the thermal stability of the alloy is mainly depends on the change of the precipitated phase. When the stabilization temperature is below 150 ℃, the T₁ phase keeps a good heat resistance, the size and quantity of precipitated phase change slightly. When the stabilization temperature rises further, the number of T₁ phase decreases gradually.

Key words: high strength and toughness Al-Li alloy, room temperature tensile property, thermal stability, fracture morphology, precipitated phase