Microstructure and mechanical properties of UFG medium carbon steel processed by HPT at increased temperature

Nanocrystalline steel obtained by mechanical alloying of iron and graphite subsequently compacted by high-pressure torsion

“…Reports about HPT of Fe-C found in the literature are not abundant, but can be found nonetheless: Ivanisenko et al also studied compacts obtained by HPT of MA Fe-C powder, however with 1 wt.% C, and after HPT performed under a pressure of 1.4 GPa and a temperature of 813 K; they found a grain size of 70 nm [32]. In other studies, carbon steel with different carbon contents was subjected to HPT, and the grain size was 200 nm after HPT of Fe-0.45 wt.% C at 7 GPa and 673 K [23], 120 nm after HPT of Fe-0.45 wt.% C at 6 GPa and 623 K [25], 10 nm after HPT of Fe-0.6-0.8 wt.% C at 7 GPa and 300 K [21], and 20 nm after HPT of Fe-1.2 wt.% C at 10 GPa and 300 K [20]. The larger grain sizes as compared to the $20 nm found in this study reported in [23,25,32] are most probably due to the elevated processing temperatures of 673, 623, and 813 K. In this study, samples containing 0.4 wt.% C were subjected to HPT at 523 K, resulting in a grain size of not more than 20 nm, while in [25] and [23], Fe-0.45 wt.% C subjected to HPT at 623 and 673 K at comparable pressures of 6 and 7 GPa, resulting in a grain size of 120 and 200 nm, respectively.…”

“…[20][21][22][23][24][25][26]. Korznikov and co-workers [20] as well as Ivanisenko et al [21,22] analyzed the changes of high carbon steel (carbon content 1.2 wt.% and 0.6-0.8 wt.%, respectively) under HPT and found complete dissolution of cementite and the evolution of structural components with a mean size of 10-20 nm, whereas Zrnik et al [23], Bayramoglu et al [24] as well as Ning et al [25] found structural components with a mean size of 100-200 nm in AISI 1045 (0. 45 after HTP [26].…”

Superior strength of carbon steel with an ultrafine-grained microstructure and its enhanced thermal stability

“…This provides an opportunity to realize a set of strengthening mechanisms in UFG carbon steels; in particular, in addition to the grain boundary strengthening mechanism, also the dislocation strengthening, precipitate strengthening and solid solution strengthening mechanisms [12,15], as well as the new strengthening mechanism associated with solute segregation at grain boundaries [15,16], make their contributions. Such a superposition of the strengthening mechanisms allows to enhance considerably the strength of carbon steels [12,[17][18][19][20].…”

Microstructure and mechanical properties of IF steel deformed during plane stress local torsion

“…4(b), a narrow band of quite severely-refined grains about 300µm wide near the edge of the hole, in a pure shearing deformation mode, can be distinguished from the rest of the material. In this heavily deformed region, where the shear strain is substantially raised, the distribution of shear strain is heterogeneous which is typical for most SPD processes involving large shearing deformations [10]. The heterogeneity is reduced as moving away from the edge of the hole in the radial direction.…”