Deformation mechanisms in ultrahigh-strength and high-ductility nanostructured FeMnAlC alloy

• Lightweight, ultrahigh-strength, ductile Fe–30Mn–9.5Al–2.0C alloy was investigated.
• Isolated γ-phase nano-channels bounded by κ′-carbides observed in the aged alloy.
• Deformation mechanism dominated by bursting dislocation nucleation was identified.
• HRTEM lattice image gave the first direct evidence of the Taylor dislocation lattice.

The deformation mechanisms of a bulk nanostructured Fe–30Mn–9.5Al–2.0C (in wt.%) alloy were investigated. After aging at 450 °C for 9–12 h, the alloy exhibits an exceptional strength-ductility combination (e.g. yield strength ∼1406 MPa with elongation ∼32%). The aged alloy exhibits a novel microstructure with isolated austenite nano-channels bounded by an extremely high volume fraction of directional nano-sized (Fe,Mn)3AlC carbides (κ′-carbides). The plastic deformation was found to be dominated by bursting dislocation nucleation within the isolated austenite nano-channels.