Identification of Hydrogen Trapping in Aluminum Alloys Via Muon Spin Relaxation Method and First-Principles Calculations

Although hydrogen embrittlement susceptibility of high-strength Al alloys is recognized as a critical issue in the practical use of Al alloys, identifying the hydrogen trapping or distribution has been challenging. In the present study, an effective approach based on experiment and simulation is proposed to explore the potential trap sites in Al alloys. At first, zero-field muon spin relaxation experiments were implemented in the temperature range from 5 K to 300 K. The plot of the temperature dependence of dipole field widths (∆) provides several characteristic peaks corresponding to the hydrogen trapping. Four dilute Al alloys (Al–Mg, Al–Cu, Al–Ti, and Al–V) were chosen to explore the possible trap sites. Atomic configurations of the muon trapping sites corresponding to the observed ∆ peaks are well assigned using the first-principles calculations for the binding energies of hydrogen around a solute and solute-vacancy pair. The extracted linear relationship between the muon ∆ peak temperature and the binding energy enables us to explore the potential alloying elements and their complex that have strong binding energies with hydrogen in Al alloys.