Suppression of hydrogen embrittlement for Al-Zn-Mg alloys processed by high pressure torsion

Al-Zn-Mg alloys exhibit a high degree of sensitivity to hydrogen embrittlement, a phenomenon that is exacerbated by their high strength. Recent studies have revealed that the interfaces of η-MgZn2 are susceptible to debonding due to elevated hydrogen concentrations. It has also been reported that such interfacial debonding can be suppressed by dispersing Mn-rich dispersoids and/or T-Al2Mg3Zn3 precipitates. In this study, we have confirmed that the afore-mentioned prevention method for hydrogen embrittlement also has efficacy in the case of Al-Zn-Mg alloys being made extremely strong, and we have adopted the high pressure torsion technique for achieving such ultra-high strength. Preparation of Al-Zn-Mg alloys containing Mn was undertaken, with the alloys exhibiting either solely the η-phase or a combination of the η-phase and the T-phase. Processing of the alloys was conducted using the HPT method. The tensile strength of the Al-Zn-Mg alloy processed by the HPT process was shown to have been improved, whereas the fracture strain was found to have been significantly increased by suppressing hydrogen embrittlement via the dispersing of both Mn-rich dispersoids and T-phase. The rationale underpinning the efficacy of Mn-rich dispersoids and T-phase in suppressing hydrogen embrittlement will be examined through hydrogen partitioning analyses.