Microstructural refinement in an ultra-high strength martensitic steel via equal channel angular pressing

In this work, a CALPHAD thermodynamic model is used to assess the thermodynamic stability of austenite in an Ultra-High Strength Martensitic Steel (i.e., Eglin Steel) in order to refine parent austenite-grain sizes, via high temperature equal-channel angular pressing (ECAP). The parent austenite-grain sizes are reduced from 188 µm to 14.8 µm, which in turn, led to the refinement of martensite lath sizes. This approach produced a yield strength of 1.68 GPa, ultimate strength of 1.98 GPa, and an elongation of 16.1%. Overall, this method reduced development cycle times and achieved alloy performance on par with Ni-Co secondary hardening steels.