The role of lithium in hydrogen trapping and embrittlement of Al-Cu-Li alloys: Experimental study and DFT calculations

• Published in: Journal of alloys and compounds 2024-06, Vol.988, p.174289, Article 174289
• Main Authors: Li, Heng-shi, Luo, Si, Xiang, Hui, Liu, Zhen-zhen, Yao, Yong, Li, Jin-feng, Tao, Hui-jin, Zhang, Rui-feng, Liu, Dan-yang
• Format: Article
• Language: English
• Subjects: Al-Cu-Li alloys; Corrosion; DFT calculation; Hydrogen embrittlement and trapping
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2024.174289

The role of lithium in hydrogen embrittlement (HE) and trapping of Al-Cu-Li alloys were investigated in experimental and density functional theory (DFT) calculations. The tensile curves and fracture morphology show that the Li-contained samples are more sensitive to HE than the Li-free samples and the HE sensitivity increases with the aging time expansion. The Transmission Electron Microscope (TEM) analyses reveal that the number density of T1 (Al2CuLi) precipitates increases about 66.8% with aging process, suggesting that HE sensitivity is exacerbated by T1 precipitates. In addition, the lithium in T1 precipitates, solid solution matrix and solute segregation grain boundaries (GBs) always has a high affinity to hydrogen according to DFT calculations, where T1 precipitates have the highest hydrogen trapping energy with 0.736 eV/H atom. Moreover, the influence of hydrogen on Al-Cu-Li alloys was investigated using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and electrochemical corrosion analysis. These analyses indicate that hydrogen exists in the form of hydrogen atoms, which results in a reduction in corrosion potential (Ecorr) from −676.3 mV to −699.3 mV by approximately 20 mV and an increase in corrosion current density (icorr) from 2.1×10−6 A/cm2 to 10.8×10−6 A/cm2 by an order of magnitude. The accumulated hydrogen atoms eventually lead to corrosion pits and blisters on the surface of alloys. [Display omitted] •The Li-contained alloys are more sensitive than the Li-free alloys to hydrogen embrittlement (HE).•The hydrogen trapping energy of T1 precipitates is higher than those of other in DFT calculations.•The trapped hydrogen atoms decrease the surface corrosion resistance and lead to the corrosion pits and cracks.•The interactions between hydrogen and lithium intensify the transformation of the ductile to brittle fracture.