Grain refinement effect on cryogenic tensile ductility in a Fe-Mn-C twinning-induced plasticity steel

► A twinning-induced plasticity steel showed degradation of uniform elongation by decreasing deformation temperature. ► Intergranular and ε/α′ boundary cracking, and fracture associated with ε-martensite were observed at 123 K. ► The cryogenic tensile properties were improved with decreasing grain size. ► One of the important reasons of the improvement was clarified to be suppression of formation of ε-martensite.