Thermal stability of nanostructured Hadfield steel produced by high-pressure torsion

Formation of epsilon martensite by high-pressure torsion in a TRIP steel

“…Further experiments are now needed to more fully clarify the origin of this second hardening stage in the present alloy. However, the validity of the present results is supported by reports of a softening at large strains in an AISI 304L alloy [18] and in SUS 304 and SUS 316L alloys [13] processed by HPT. These latter alloys also exhibit a phase transformation during HPT processing.…”

“…The dissolution of cementite at large strains was reported in a UIC 860V steel (Fe, 0.6-0.8% C, 0.8-1.3% Mn, 0.1-0.5% Si, 0.04% P(max), 0.04% S(max)) [9] and this material also exhibited higher thermal stability of the ferrite grains [8]. Twinning was observed in Fe13Mn-1.3C, Fe-13Mn-2.7Al-1.3C and Fe-28Mn-2.7Al-1.3C processed by HPT and, in addition, there were small fractions of epsilon ε and alpha prime α' martensite [18]. Similar results were reported in a Fe-24% Mn-3% Al-2% Si-1% Ni-0.06% C steel [17].…”

“…In this operation, a sample in the shape of a thin disc is compressed between rigid anvils and subjected to torsional straining. Processing by HPT has been used with iron [5,6] and different steels [6][7][8][9][10][11][12][13][14][15][16], including twinning induced plasticity steels [17][18][19] which also exhibit very high uniform elongations at room temperature. A review of these data shows that different effects were reported during the processing of iron and steels by HPT.…”

The effect of high-pressure torsion on microstructure and strength properties of high-nitrogen austenitic steel

“…There are very few papers on SPD of austenitic steels with a high concentration of interstitial atoms as they undergo severe strain hardening as a consequence of deformation, require high pressure to achieve deformation, and can cause destruction of equipment. However, using single crystals of highmanganese austenitic steels with high carbon concentrations in papers [3,4] the authors show the possibility of forming the structure comprising high density of special boundaries (twinning) under SPD. In paper [5], using austenitic steels Fe-13.4Mn-1.3C, Fe-10.1Mn-0.71C, Fe-4.3Mn-1.12C (wt.%) with high concentrations of carbon atoms the authors formed polycrystalline structures with a crystallite sizes of 0,01-0,5 µm in them using high-pressure torsion (HPT) (6-15 GPa) at room temperature.…”

“…Such behaviour is due to the dependence of the strain from the centre to the edge of the sample e ~ ln r [2]. However, for example, in the samples of stable high-strength steels with a high concentration of carbon atoms and low stacking fault energy [4] or metastable Cr-Ni steel [13] after HPT, the authors observed homogeneous microhardness distribution that was caused by the formation of high density of twin boundaries in the structure in one case and by straininduced phase γ-α' transformation in another one.…”