Ultra-High-Strength Interstitial-Free Steel Processed by Equal-Channel Angular Pressing at Large Equivalent Strain

Bulk Ultrafine-Grained Interstitial-Free Steel Processed by Equal-Channel Angular Pressing Followed by Flash Annealing

“…Due to limited amount of processed material, the bulk mechanical property like tensile testing could not be performed on all materials. From the measured hardness value and tensile test data reported elsewhere (Ref 33,34), ratio of hardness to yield strength is calculated in two regions-one in deformed state and other well-annealed state. From these ratios, yield strength is calculated using measured hardness values for different flash-annealed IF steel [43].…”

“…The theoritical hardness values are calculated from Hall-Petch constants (Ho and K, calculated from a fit by method of least square from experimental hardness values) within the grain size range. From the measured hardness value and tensile test data reported elsewhere (Ref33,34), ratio of hardness to yield strength is calculated in two regions-one in deformed state and other well-annealed state. From these ratios, yield strength is calculated for both the regions in the present experimental conditions for different flash-annealed IF steels from the theoretical harness values.…”

Improvement of fracture toughness of Ti+Nb stabilized microalloyed and interstitial free steels processed through single phase regime control multiaxial forging

“…Among different processing techniques, severe plastic deformation (SPD) technique is the most promising technique to develop bulk size ultrafine grained (UFG) materials, where, the majority of the grain boundaries exhibits high angles of misorientation [3,4]. Several SPD techniques have been extensively exploited to develop UFG materials through different powerful straining methods such as high pressure torsion, equal channel angular extrusion and accumulative roll bonding [5,6]. Till now, as per the available literature, the maximum grain size refinement of IF and low carbon (C) steel is reported to be ~0.3 and 0.2µm, respectively, processed by ECAP technique at large equivalent strain of 24 and 17.…”

“…Till now, as per the available literature, the maximum grain size refinement of IF and low carbon (C) steel is reported to be ~0.3 and 0.2µm, respectively, processed by ECAP technique at large equivalent strain of 24 and 17. The maximum improvement of YS is reported to be 895 and 913MPa along with a ductility of 11 and 10.6%, respectively, for IF and low C steels [5,7]. However, expensive tooling are required for most of these techniques, and there is a design difficulties also.…”

“…The mechanism of grain refinement during multiaxial forging is enlightened through the intersection of microshear bands, which are formed owing to strain localization; and bring about the evolution of subgrains. On further straining, as the subgrain boundaries absorb dislocations, the subgrains transform into grains by rotation, instead of growth [5,10]. Growth process generally occurs when deformation carried out at elevated temperatures, which allows dislocations to both glide and climb [1,2].…”