预变形对Al-4.28Cu-1.33Li-0.40Mg-0.30Ag-0.14Zr合金时效组织与性能的影响

采用室温拉伸、透射电镜观察等手段, 研究了3%拉伸预变形对Al-4.28Cu-1.33Li-0.40Mg-0.30Ag-0.14Zr合金单级和双级时效组织与性能的影响。拉伸结果表明, 对于190 ℃/(3~7) h的单级时效处理, 3%拉伸预变形可以提高拉伸强度56~75 MPa, 时效时间延长, 预变形提高强度的效果大幅度降低。3%拉伸预变形可以使得190 ℃/7 h+100 ℃/24 h双级时效样品的强度提高81 MPa, 达到748 MPa。透射电镜观察结果表明, 190 ℃/7 h单级时效态样品对应的组织主要为T₁和θ'相, 还有少量S'相; 190 ℃/7 h+100 ℃/24 h双级时效态样品在190 ℃/7 h时效组织基础上析出了大量δ'相; 而在190 ℃/7 h+100 ℃/24 h双级时效前施加3%拉伸预变形则极大地促进了T₁相和θ'相的析出, 从而大幅度提高合金抗拉强度, 而δ'相的析出受到抑制。

Effect of Pre-strain and Aging Treatment on the Microstructure and Properties of Al-4.28Cu-1.33Li-0.40Mg-0.30Ag-0.14Zr Alloy

The effect of one-step and two-step aging treatment with 3% pre-strain at room-temperature on the microstructures and properties of Al-4.28Cu-1.33Li-0.40Mg-0.30Ag-0.14Zr alloy was investigated by using tensile testing and transmission electron microscopy (TEM). The tensile testing results show that the 3% pre-strain prior to one-step aging treatment at 190 ℃/(3～7) h can increase the tensile strength by 56～75 MPa. However, this effect will be greatly decreased with the prolongation of the aging time. It is found that the 3% pre-strain prior to two-step aging treatment at 190 ℃/7 h+100 ℃/24 h can increase the strength of the alloy by 81 MPa to 748 MPa. The TEM observation shows that alloy sample after one-step aging treatment (190 ℃/7 h) are dominated by T₁ and θ' phases with a small amount of S' phase in the structure. And two-step aging treatment at 190 ℃/7 h+100 ℃/24 h brings a large precipitation of δ' phases in the structure based on the previous aging treatment. Furthermore, 3% pre-strain prior to two-step aging treatment at 190 ℃/7 h+100 ℃/24 h can greatly promote the precipitation of T₁ and θ' phases, leading to the tensile strength greatly increased, but the precipitation of δ' phase is inhibited.