采用光学显微镜(OM)、透射电镜(TEM)、扫描电镜(SEM)、维氏硬度计和力学性能测试等方法研究了Li元素对Al-3.5Cu-1.5Mg合金微观结构及性能的影响。结果表明:在Cu/Mg原子比约为1的Al-3.5Cu-1.5Mg实验合金中,加入1%(质量分数)的Li元素,主要时效析出相由S′(Al2CuMg)转变为S′(Al2CuMg)+δ′(Al3Li),晶界无沉淀析出带(PFZ)窄化;弹性模量提高了8GPa,抗拉强度提高了21MPa,伸长率由20.3%降至15.8%,由韧性断口转变为韧/脆混合型断口。
The effect of Li on microstructures and properties of Al-3.5Cu-1.5Mg alloy was studied by optical microscopy (OM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Vickers hardness(HV)and electronic tensile test respectively. The results show that the addi- tion of 1% Li (mass fraction) translates the main precipitation phase Sr(Al2CuMg) to S′ (Al2CuMg) + δ′(Al3Li) in the alloy, which Cu/Mg atom ratio is about 1. Precipitate free zones (PFZs) are nar- rowed. Elastic modulus increases by 8GPa. The tensile strength is improved by 21MPa. However, the elongation of the alloy decreases from 20.3% to 15.8%. The form of fracture morphology is changed from ductile fracture to ductile/brittle mixed fracture.