Suppression of Hydrogen Embrittlement due to Local Partitioning of Hydrogen to Dispersed Intermetallic Compound Particles in Al–Zn–Mg–Cu Alloys

Abstract

Recent studies have revealed that hydrogen embrittlement in AlZnMg alloys appears to be dominated by hydrogen partitioning to MgZn 2 precipitates. A method has recently been proposed for reducing the hydrogen concentration at MgZn 2 precipitates by adding specific intermetallic compound particles that have high hydrogen trap energy. In the present study, the effectiveness of Al 7 Cu 2 Fe particles on suppression of hydrogen embrittlement in AlZnMgCu alloys was evaluated using X-ray microtomography. Quasi-cleavage cracks were found to be initiated in regions where local volume fractions of the Al 7 Cu 2 Fe particles were relatively low. Hydrogen partitioning to the MgZn 2 precipitate interface was suppressed, even in high hydrogen concentration material, by adding Al 7 Cu 2 Fe particles. However, the fractional area of the quasi-cleavage fracture in the material with high hydrogen concentration was higher due to insufficient hydrogen diffusion inside the Al 7 Cu 2 Fe particles and at the interface between the aluminum matrix and the particles. It appears that finely distributed small Al 7 Cu 2 Fe particles might effectively suppress hydrogen embrittlement.

Best Papers Awarded by JILM and JSTP in <i>Materials Transactions</i>

“…2) was different from the thermodynamic calculations using the existing database, whereas such a result was found in conventional Al-Mg-Zn-Cu alloys. 33,34) The added Ni element enhanced the formation of the fine Al 3 Ni phase located at grain boundaries (Fig. 3) and slightly influenced the precipitation of the T phase in the grain interior.…”