热处理制度对新型Al-Cu-Li合金组织与性能的影响

Effect of heat treatment on microstructure and properties of new Al-Cu-Li alloy

采用硬度测试、力学性能测试、SEM、EDS和TEM分析等方法,研究不同固溶处理和时效处理制度对新型Al-Cu-Li合金组织与性能的影响。结果表明:合金经490℃、1.5 h固溶处理后,第二相粒子回溶充分,未回溶第二相为Al Cu Fe Mn相,合金断口形貌呈沿晶断裂与少量韧窝形貌混合特征。合金适宜的T6制度为175℃、48 h,抗拉强度、屈服强度和伸长率分别为447 MPa、369 MPa和8.9%。适宜的T8制度为预变形6%+(160℃、36 h),抗拉强度、屈服强度和伸长率分别为500 MPa、454 MPa和10.5%,此时合金具有较好的强塑性匹配。合金在T6和T8态的强化相均为复合相δ′/β′相、θ′相和T_1相3种。时效前的预变形可显著提高合金强度,随预变形量的增加,合金强化相由δ′/β′相、θ′相和T_1相为主逐渐转向以T_1相为主,T_1相比θ′相、δ′相具有更佳的强化效果。

The relationship between microstructures and properties of a new Al-Cu-Li alloy under different solid solution and aging treatments were studied by hardness test, tensile test, SEM, EDS and TEM analysis. The results show that the second phase particles of the alloy are fully dissolved by solid solution treatment at 490 ℃ for 1.5 h, and the remaining second phase is AlCuFeMn phase. The fracture mode of the alloy is characterized by intergranular fracture and small dimple mixed fracture. The suitable T6 temper of the alloy is （175 ℃, 48 h）, and the corresponding tensile strength, yield strength and elongation rate are 447 MPa, 369 MPa and 8.9%, respectively. The suitable T8 temper of the alloy is 6%＋（160 ℃, 36 h）, and the corresponding tensile strength, yield strength and elongation rate are 500 MPa, 454 MPa and 10.5%, respectively. The alloy shows excellent combination of strength and ductility when the pre-deformation ratio is controlled at about 6%. The strength phase of the alloy are composite phase δ′/β′, θ′ and T1 in T6 and T8 temper. The pre-deformation greatly improves the strength of the alloy. With the increase of the pre-deformation, the mainly strengthening phase of the alloy gradually change from δ′/β′, θ′ and T1 to the T1 phase. T1 has better strengthening effect compared with δ′/β′ phase and θ′ phase.