Evaluation of stacking-fault energy in Fe-Mn based twinning-induced plasticity steels after friction stir welding

Highlights: • Stacking-fault energy (SFE) of TWIP steels after friction stir welding is measured. • Measured SFE matches with calculated SFE. • Dislocation accumulation and grain refinement by friction stir welding increases SFE. • Max. increment of SFE is ~15 mJ m⁻². -- Abstract: The stacking-fault energies (SFE) of three Fe-18Mn-0.6C-(0, 1.5)Al and Fe-30Mn-3Al-3Si (wt%) twinning-induced plasticity (TWIP) steels after friction stir welding (FSW) were quantitatively evaluated by X-ray diffraction (XRD) and thermodynamic calculations. The measured SFE values using the XRD comparatively matched with the calculated SFE values using the thermodynamic calculations. The SFE values increased from 13.0 to 27.4 mJ m⁻² for the 0Al, from 29.0 to 34.4 mJ m⁻² for the 1.5Al and from 54.4 to 68.0 mJ m⁻² for the 30Mn steels due to the introduction of dislocation and grain refinement after the FSW. For the design of TWIP steels after joining, the FSW effect on the SFE needs to be considered.