在不同温度和保温时间下对2A12铝合金冷轧板进行了人工时效处理，通过显微硬度和室温拉伸实验测试了合金的力学性能，对不同时效阶段合金的微观组织和析出相进行了表征。研究发现，2A12铝合金冷轧板具有单个时效峰，时效温度越高，达到峰值时效所需的时间越短，时效温度与时间对其力学性能均具有较大影响。随时效时间的增加，合金断裂方式由韧性断裂逐渐转变为沿晶韧窝断裂和穿晶断裂。时效初期合金主要为Cu-Mg团簇强化，峰值时效时为Cu-Mg团簇和GPB区强化，过时效时析出相逐渐转化为稳定的S (Al₂CuMg)相。在考虑均质形核与非均质形核的共同作用下，2A12铝合金冷轧板的时效脱溶析出序列为过饱和固溶体(SSS)→Cu-Mg团簇+S_inhomo→Cu-Mg团簇+GPB区+S_inhomo→Cu-Mg团簇+GPB区+S_homo+S_inhomo→S。

2A12 Al alloy has been widely applied in the fields of aviation, aerospace, and vehicles due to its light weight, high specific strength and good corrosion resistance. The solution and ageing treatments are usually performed after the processing on 2A12 Al alloy, and the ageing parameters greatly affect the final mechanical properties. In the present study, the artificial ageing was performed on the cold rolled 2A12 Al sheet under various holding temperatures and holding time. The mechanical properties were evaluated by micro-hardness and tensile tests. Moreover, the evolution of microstructure and precipitations during ageing with different holding time were characterized. The results showed that the 2A12 Al sheet had the sole peak ageing, and the higher the temperature, the shorter time was required for the peak ageing. Both the holding temperature and holding time significantly affected the mechanical properties. The optimal ageing parameters were determined as holding at 185 ℃ for 16 h, and the corresponding yield strength, ultimate tensile strength and elongation along rolling direction were 381 MPa, 476 MPa and 13.6%, respectively. S (Al₂CuMg) phase gradually precipitated during ageing process, and the size and distribution of S phase greatly affected the fracture mechanism. At the initial stage of ageing, S phase precipitated near grain boundaries, and the ductility fracture could be observed. With the extension of holding time, the coarsening of S phase took place, and the fracture was gradually transformed to intergranular and transcrystalline modes. Cu-Mg cluster was the main strengthening mechanism at the initial stage of ageing. Both Cu-Mg cluster and GPB zone contributed to the strengthening under the peak ageing, and the precipitations were transformed to stable S phase under the over ageing. Considering the combined effects of homogeneous and inhomogeneous nucleation, the precipitation during ageing of cold rolled 2A12 Al sheet followed the sequence of supersaturated solid solution (SSS)→Cu-Mg cluster+S_inhomo→Cu-Mg cluster+GPB zone+S_inhomo→Cu-Mg cluster +GPB zone+ S_homo+S_inhomo→S.