Hydrogen desorption behavior in Al-8%Zn-1%Mg alloy

The increase in Zn or Mg content results in an increase in Al-Zn-Mg alloys strength, however they become more susceptible to hydrogen embrittlement. To understand the hydrogen embrittlement behavior, it is necessary to study the hydrogen trapping behavior. In the present study, Al-8%Zn-1%Mg was made in order to have six trap sites (vacancies, dislocations, grain boundaries, particles, precipitates and micropores) and hydrogen trapping behavior in those trap sites was assessed by means of thermal desorption analysis (TDA). In addition, micropores were evaluated in detail using X-ray microtomography. Hydrogen desorption energies from grain boundaries and micropores were calculated using TDA curves. These values were 2 to 3 times larger than the ones reported in the literature due to a change in the trap sites during thermal desorption test. Increase in the number density of micropores was observed above 673 K during thermal desorption experiment. As the temperature increases, it has been reasonably inferred that some hydrogen desorbed from trap sites are released from the specimen and the rest of hydrogen is redistributed to form new micropores. It is revealed that low heating rate induces a change in trap sites and affect the measurement of hydrogen desorption energies.