Hydrogen embrittlement in high manganese lightweight steel
In this project we study the degradation of hydrogen embrittlement resistivity of austenitic high-Mn and high-Al lightweight steels upon age hardening and discover ways to mitigate this deterioration.
While age-hardened austenitic high-Mn and high-Al lightweight steels exhibit great strength-ductility combinations, their properties are strongly degraded when loaded under harsh environments, e.g. with the presence of hydrogen (H). The H embrittlement in this type of materials, especially pertaining to the effect of κ-carbides precipitation, has been scarcely studied. Here we focus on this subject in a Fe-28.4Mn-8.3Al-1.27C (wt.%) steel with different microstructure conditions, namely, solute solution treated and age-hardened. Contrary to the reports that grain boundary (GB) κ-carbides precipitate only during overaging, site-specific atom probe tomography (APT) and scanning transmission electron microscopy (STEM) reveal the existence of nanosized GB κ-carbides at early stages of aging. We study the effect of these precipitates on hydrogen embrittlement susceptibility of the alloy and use the acquired knowledge to investifate possible alloying and microstructure adjusting strategies for the enhancement of the H embrittlement resistance in this alloy family.