中文摘要：

对一种含少量Mg、Zn的Al-Cu-Li合金经过T6（固溶＋人工时效）和T8（固溶＋预变形＋人工时效）热处理后的显微组织进行研究。结果表明：该合金在（T6,170℃）峰时效时析出大量的立方相,而在（T6,120℃）和（T6,190℃）峰时效时却没有发现立方相的大量存在。T1相和立方相之间可能存在一种竞争析出关系,而温度和预变形因素制约着这种竞争析出关系。利用MonteCarlo方法模拟时效初期该合金的原子分布,分析其立方相的形成机理。模拟结果表明：在（T6,170℃）峰时效初期,Mg-Zn团簇周围的Cu、Mg原子富集区成为立方相形成的理想形核点。同时,Mg团簇周围区域内较高的空位浓度也有利于溶质原子的快速扩散。因此,Mg-Zn原子团簇应是立方相形核的关键因素。

英文摘要：

The Al-Cu-Li alloys with addition of trace elements of Mg and Zn,treated by T6（solution treatment＋artificial aging）and T8（solution treatment＋pre-deformation＋artificial aging）,were studied.The experiment results show that a lot of new cubic phases precipitate when the alloy is aged under the peak-aged condition of（T6,170 ℃）,but this case dose not be found in the alloys aged under the peak-aged conditions of（T6,120 ℃） and（T6,190 ℃）.There exists a competitive precipitation relationship between T1 phase and cubic phase,which is restricted by the factors of temperature and pre-deformation.Monte Carlo method was used to simulate the atom distribution in the alloy during initial aging stage and analyze the forming mechanism of the cubic phase.The simulation results show that during the initial aging stage of（T6,170 ℃）,the Cu-Mg atom enrichment zones around Mg-Zn clusters become the perfect nucleate points for the cubic phase formation.Meanwhile,the higher vacancy concentration around Mg clusters is beneficial to quick solute diffusion.Thus,the Mg-Zn atom clusters may be the key factor of the formation of cubic phase.