过时效工艺对AA2195铝锂合金微观组织的影响

采用扫描电子显微技术（SEM）、透射电子显微技术（TEM）、背反射电子衍射技术（EBSD）等分析手段对AA2195铝锂合金过时效对析出相粒子组态、细晶组织的影响进行了研究。结果表明：时效过程中析出的球状粒子为富Cu相，板条状相为富CuFe相；在相同的时效时间下，越高的处理温度可以得到更大的析出相粒子体积分数；在600K以下时效时，粒子沿原始晶界呈连续分布，并几乎占满所有晶界，这种网状分布的粒子在最终快速退火中不仅无法提供足够的形核位置，还将成为大角度晶界移动的障碍，导致大尺寸扁平状晶粒组织的形成，而600K以上的样品则可以得到球状粒子，晶界上无连续分布的粒子，得到了比较理想的晶粒组织。600K／24h炉冷是AA2195铝锂合金超塑性预处理的最佳时效工艺。

Influence of over-aging technology on microstructure of AA2195 Al-Li alloy

The influence of over-aging treatment of AA2195 on the distribution of second phase particles was investigated by SEM, TEM, and electron back scatter diffraction(EBSD).It is found that the spherical particles and lath particles precipitated during aging are Cu-rich phase and Fe-rich phase,respectively.For the same aging time, higher aging temperature increases fraction of precipitated particles and modified their morphology.Aging temperature lower than 600K, the precipitated particles are continuously distributed all over the grain boundaries, which will not only offer effective recrystallization nucleation sites, but also hinder migration of large angle boundaries, and leads a lamellar grain structure. However, aging at temperature higher than 600K results in a uniform distribution of spherical particles and no continuous distribution of small particles on grain boundaries is observed,and thus a fine equiaxed grain structure is obtained. The treatment of aging at 600K for 24 hours followed by furnace cooling is the optimum technology for a fine equiaxed grain structure in the AA2195 alloy sheet.