微量元素铈对Al-Li-Cu-Mg-Ag-Zr合金强化和断裂机制的影响

摘要

Effects of trace Ce on strengthening and fracture mechanisms of Al-Li-Cu-Mg-Ag-Zr alloy were investigated by fracture failure tests, SEM and TEM. Results show that the addition of trace Ce element doesn't change the sorts of main strength precipitates, T1(Al2CuIi) and θ'(Al2Cu) , but can facilitate small T1 distributing dispersively and homogeneously and improving alloy's strength and toughness with reduction of ductility simultaneously. With an increase in concentration of Ce, the density of T1 precipitation increases with more even distribution, which benefits for strength improvement further. The strength of alloy containing 0. 3% Ce is higher than that of alloy containing 0. 15% Ce and the alloy containing Ce has an advantage of fracture toughness compared with alloy containing little Ce. Trace Ce can make contribution to microstructures delamination, to some extent, which is beneficial to alteration of fracture failure and reduction of intergranular failure. SEM analysis of fracture toughness demonstrates that morphologies of failure transform from intergranular-brittle to transgranular-intergranular delaminated forms.%采用断裂性能测试、扫描电镜(SEM)断口分析、透射电镜(TEM)观察等手段研究了微量元素Ce对Al-Li-Cu-Mg-Ag-Zr合金强化和断裂机制的影响.实验结果表明:添加微量元素Ce并不改变合金主要强化析出相(T1、θ')的种类,但是能够促进T1相细小均匀弥散分布,提高合金强度以及断裂韧性.随着Ce含量的增加,T1相析出密度越大,分布越均匀,强化效果越好.添加0.3％Ce的合金强度明显高于添加0.15％ Ce的合金,添加Ce的合金断裂韧性明显高于不加Ce的合金,并且Ce能够使合金组织分层薄化,在一定程度上改变合金的断裂行为方式,减少了沿晶断裂的趋势.断裂韧性断口扫描分析表明,合金的断裂方式随Ce含量的增加逐渐由沿晶脆性断裂转变为穿晶-沿晶分层断裂方式.