The effect of nitrogen on microstructural evolution and tensile properties of transformation-induced plasticity (TRIP) Fe50Mn30Co10Cr10 HEAs was investigated.Nitrogen was fully introduced in solid solution by pressure-induced melting technique.Nitrogen addition turned the TRIP alloy to a twinning-induced plasticity (TWlP) alloy,and simultaneously improved the strength and elongation.For the nitrogen-doped HEA,the high yield strength is mainly resulted from the friction stress via interstitial strengthening effect,and the high ductility is originated from retained high strain-hardening capability via the successive onset of dislocation accumulation and deformation twinning.The strain-hardening behavior and microstructural evolution at specified strains were revealed.