Effect of Ag addition on the age hardening and precipitation behavior in an Al-Cu-Li-Mg-Zn-Mn-Zr alloy

• Published in: Materials characterization Vol. 162; p. 110184
• Main Authors: Jiang, Bo, Wang, Haisheng, Yi, Danqing, Tian, Yu, Shen, Fanghua, Wang, Bin, Liu, Huiqun, Hu, Zhan
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.04.2020
• Subjects: Al-Cu-Li-Mg-Zn-Mn-Zr alloy; Cubic σ phase; Microstructure; T1 phase; T1 phase; Cubic σ phase; Al-Cu-Li-Mg-Zn-Mn-Zr alloy; Microstructure; Ag
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2020.110184

Effect of Ag addition on the age hardening and precipitation behavior of an Al-Cu-Li-Mg-Zn-Mn-Zr alloy has been investigated by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) with an energy dispersive X ray spectroscope (EDS), convergent beam electron diffraction (CBED) and hardness. The results showed that the precipitation behavior of the Ag free Al-Cu-Li-Mg-Zn-Mn-Zr alloy was SSS → δ′/GP zone/δ′ + T1 → cubic σ phase + θ′ + T1 + S′/S phase, while in the Ag added Al-Cu-Li-Mg-Zn-Mn-Zr alloy, it was SSS → θ′ + δ′ + T1 → θ′ + δ′ + T1 + S′/S phase. The Ag added alloy exhibited higher strength than the Ag free alloy due to a promoted T1 precipitation, while the hardness loss of the Ag free alloy was smaller than that of the Ag added alloy due to the precipitation of cubic σ phase. Ag was mainly concentrated in T1 precipitates and stimulated the precipitation of T1 rather than providing nucleation sites for cubic σ phase. Hence, the precipitation of cubic σ phase was suppressed by competing with T1 for solutes in the Ag added Al-Cu-Li-Mg-Zn-Mn-Zr alloy. •The main precipitates in the peak aged Ag free alloy were cubic σ phase and T1.•The main precipitates in the peak aged Ag added alloy were T1.•The Ag added alloy exhibits higher hardness due to the promoted T1 precipitation.•The Ag free alloy exhibits better thermal stability due to the precipitation of σ.•Ag tends to segregate in T1 rather than in cubic σ phase.