通过拉伸试验机、腐蚀试验箱、DSC以及TEM等手段对淬火后预拉伸处理并自然时效至稳定状态的铝锂合金薄板的拉伸性能、腐蚀性能、时效响应特征以及微观组织进行了研究. 结果表明, 在0~6%范围内, 合金的屈服强度随预拉伸量的增加而逐渐提高; 预拉伸量低于3%时, 合金的抗拉强度随拉伸量增加逐渐降低, 在3%~6%范围内, 抗拉强度趋于平稳; 随预拉伸量增加, 合金由明显的晶间腐蚀转为点蚀, T34状态点蚀深度最小, 约为0.03 mm; 预拉伸改变了合金的时效响应特征, 使合金在100 ℃附近的吸热峰向高温移动, 180 ℃及260 ℃附近的放热峰向低温区移动. 淬火后的预拉伸在增加晶内位错密度的同时, 抑制了δ’相在晶内和晶界的析出, 预拉伸量越大, 晶内及晶界δ’相的数量越少. 位错及析出相的共同作用影响了合金的拉伸及腐蚀性能.

Al-Cu-Li-X alloy has attractive applications in the aerospace and aeronautic industry due to its excellent combination of mechanical properties and corrosion resisting properties. However, the microstructural complexity, especially the type and distribution of precipitates have effects on the properties. Besides changing the chemical compositions of alloy, the preaged stretch after quenched and aging process is the main method to control the type and distribution of precipitates. In this work, the effect of preaged stretch after quenched on tensile properties, corrosion property, aging response and microstructure of a naturally aged Al-Li alloy were studied by DSC, TEM, tensile test and corrosion test. The results show that the yield strength increases gradually at the stretch range from 0 to 6%, ultimate tensile strength decreases with the increase of stretch from 0 to 3%, and then become stable when stretch over 3%. Accompany with the increasing stretch, the corrosion type of alloy changes from intergranular corrosion to point corrosion. The T34 state of alloy has the least corrosion depth, about 0.03 mm. The aging response character of alloy is changed by preaged stretch. Compared with T4 state, the endothermic peak near 100 ℃ move to higher temperature, and two exothermic peaks near 180 ℃ and 260 ℃ move to lower temperature in T3x state, respectively. Preaged stretch after quenched restrains the precipitation of δ’ phase in grain and grain boundary with increasing the density of dislocation in grains. The variations of δ’ phase and dislocation affect the tensile and corrosion properties of alloy.