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采用拉伸实验、扫描电子显微分析(SEM)、透射电子显微分析(TEM)、高分辨电子显微技术研究Li添加对Al-3.5Cu-1.5Mg合金力学性能与时效析出行为的影响。结果表明:添加1.0%Li能使Al-3.5Cu-1.5Mg合金的峰值时效拉伸强度明显提高,伸长率略有下降。峰值时效拉伸样品的断口形貌由韧断口转变为韧/脆混合型。Li使合金185℃峰值时效时间由12 h延长至24 h,析出相由S′(Al_2CuMg)转变为S′(Al_2CuMg)+δ(Al_3Li)。在Al-3.5Cu-1.5Mg-1.0Li合金中,S(Al_2CuMg)相时效析出延缓。
The tensile test, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution electron microscopy were used to study the effect of Li addition on the mechanical properties and aging precipitation behavior of Al-3.5Cu-1.5Mg alloy. The results show that the addition of 1.0% Li can significantly improve the peak aging tensile strength and decrease the elongation of Al-3.5Cu-1.5Mg alloy. The fracture appearance of the peak-aged tensile specimens was changed from ductile fracture to ductile / brittle mixture. Li prolongs the peak aging time of the alloy at 185 ℃ from 12 h to 24 h, and the precipitated phase changes from S ’(Al 2 CuMg) to S’ (Al 2 CuMg) + δ (Al 3 Li). In Al-3.5Cu-1.5Mg-1.0Li alloy, S (Al 2 CuMg) phase precipitation delayed aging.