Hydrogen Isotope Trapping in Al-Cu Binary Alloys

TL;DR

This study investigates hydrogen isotope trapping mechanisms in Al-Cu alloys, identifying a new trap site associated with Al-Cu intermetallic precipitates and quantifying its binding energy and occupancy.

Contribution

It reveals a novel hydrogen isotope trap at Al-Cu intermetallic precipitates with specific binding energy and high occupancy, expanding understanding of hydrogen behavior in aluminum alloys.

Findings

Identified Al-Cu precipitates as hydrogen traps with binding energy of 18 kJ/mol.

High occupancy of the precipitate trap in Al-2.6 at.% Cu alloy.

Precipitate trap accounts for one-third of bound deuterium in charged samples.

Abstract

The trapping mechanisms for hydrogen isotopes in Al-X Cu (0.0 at.% < X < 3.5 at.%) alloys were investigated using thermal desorption spectroscopy (TDS), electrical conductivity, and differential scanning calorimetry. Constant heating rate TDS was used to determine microstructural trap energies and occupancies. In addition to the trapping states in pure Al reported in the literature (interstitial lattice sites, dislocations, and vacancies), a trap site due to Al-Cu intermetallic precipitates is observed. The binding energy of this precipitate trap is ($18\pm3$) kJ$\cdot$mol$^{-1}$ ($0.19 \pm 0.03$ eV). Typical occupancy of this trap is high; for Al-2.6 at.% Cu (a Cu composition comparable to that in AA2219) charged at 200{\deg}C with 130 MPa D$_2$ for 68 days, there is ca. there is $3.15\times10^{-7}$ mol D bound to the precipitate trap per mol of Al, accounting for a third of the D in the charged sample.