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A new 0.25C2Cr10Ni8Co2Mo2Al steel was designed and fabricated by vacuum induction melting, forging and heat treatments. Excellent mechanical properties with a combination of a 2.4 GPa ultimate tensile strength, a 2.1 GPa yield strength, a 11.4% total elongation and a 37 J/cm2 V-notch impact toughness were obtained. Such a combination of strength–ductility–toughness of the present steel is much superior than any reported conventional ultrahigh strength steel. The excellent mechanical properties of the steel can be well interpreted by synergistic strengthening of high-density dislocations, strong segregations of C, Mo and Cr on dislocations and massive nanosized NiAl precipitations. An extra-high strength steel of 0.25C2Cr10Ni8Co2Mo2Al was designed and the combined properties could be well interpreted by the microstructure featured with high dense precipitation of NiAl particle, high dense dislocations and the co-segregation of Cr, Mo and Co. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The deformation response of a (Nb, V) micro-alloyed FeMnAlC low density steel has been investigated as a function grain size using samples subjected to different solution-treatment conditions. Mechanical properties have been characterized by tensile testing, and the microstructure before after tensile deformation has been quantified using electron back scattered diffraction and transmission electron microscopy. The deformation microstructure evolution during tensile deformation was dominated by a planar slip mode, leading to slip-band formation and a rapid refinement in microstructural scale. A detailed analysis of the relationship between microstructure and mechanical properties reveals a strong dependence of the yield stress on the initial grain size, as well as a variation of the friction stress and Hall-Petch slope on the level of applied tensile strain. The results suggest that the flow stress in the investigated low-density steel is strongly coupled with the dynamic nature of the increased Hall-Petch slope and the increased friction stress for dislocation movement. Based on this a model is proposed to simulate the stress-strain curves during tensile deformation of the low-density steel over a wide range of strain. [ABSTRACT FROM AUTHOR]