A D V A N C E D M A T E R I A L S & P R O C E S S E S | A P R I L 2 0 2 2 9 ALUMINUM ALLOY BEHAVIOR Researchers at the Max Planck Institute for Iron Research (MPIE), Germany, are studying hydrogen in aluminum alloys at the atomic level in order to more efficiently prevent hydrogen embrittlement and found first approaches to hindering this effect. The MPIE researchers used 7xxx aluminum, a highstrength aluminum class that is the primary material of choice for structural components of airplanes. They charged their samples with hydrogen and performed tensile tests showing that the ductility decreases with increasing amounts of hydrogen. The fracture surface showed that cracks especially propagated along grain boundaries. Through cryo-transfer atom probe tomography, the scientists revealed that hydrogen gathered along those grain boundaries. They were able to show where hydrogen is located following its ingress during the material’s processing or in service. Essentially unpreventable, it is important to control its trapping. The researchers recommend different strategies to prevent hydrogen embrittlement, in particular using intermetallic particles that could trap hydrogen inside the bulk material. Additionally, control of the magnesium level at grain boundaries appears critical. “Magnesium paired with hydrogen at grain boundaries increases the embrittlement,” says lead researcher Huan Zhao. “At the same time, we must manipulate the correct size and volume fraction of particles in the bulk to trap hydrogen while maintaining the material’s strength.” The researchers are pursuing further studies on perfect particle distribution and eliminating magnesium decoration of grain boundaries to design advanced high strength, hydrogen-resistant aluminum alloys. www.mpie.de/2281/en. An aluminum-based alloy with zinc, magnesium, and copper studied after aging for 24 hours at 120°C, (a) and (b) electron imaging of an intergranular crack of the hydrogen-charged alloy subjected to tensile fracture. GB: grain boundary; GBPs: grain boundary precipitates. Courtesy of Nature. (a) (b)
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