Substructural phase transitions during intense plastic deformation of low-carbon ferrite-perlite steel

Relation of Physical-Mechanical Properties to the Structural Condition of Severely Deformed Patented Carbon Steels at Drawing

“…As is confirmed by numerous experimental data [8][9][10][11][12][13], during wire drawing, the average size of cementite and ferrite layers in pearlitic steels varies proportionally with a change in the wire diameter.…”

“…The necessity of such a comprehensive study of this phenomenon is determined by the fact that the degree of cementite decomposition in a steel with the structure of fine-lamellar pearlite essentially affects the plasticity margin and, hence, the final level of strengthening and the whole complex of properties after deformation [7]. The effect of cementite decomposition upon plastic deformation has been detected by the methods of thermomagnetic analysis [14-16, 22-24, 41], electron microscopy [6,7,11,35,36], and the Mössbauer effect [14,21,22,35]. It has been found that the rate of cementite decomposition in severely deformed steel is 30 to 50% and related to the type of a certain dislocation structure in the ferrite layers of pearlite.…”

“…Note that all studies aimed at investigating the given phenomenon indicate the heterogeneity of the cementite-decomposition process due to a nonuniform distribution of dislocations and their conglomerations. For example, it is shown in [11] that, after drawing a low-carbon steel to 50%, the volume fraction of cementite decreased on average from 3.6 to 1.5% and the nonuniformity of its volume content drastically increased. In different regions, cementite volume fractions changed by 0.1-2.1%.…”

“…Since the decomposition of cementite is accompanied by depletion of its bulk of carbon [7,11,13,19], for explanation of an increase in M s , we enlisted the results of study [62], where the energy-band structure of cementite was calculated with allowance for the nonstoichiometry in the carbon sublattice. It has been shown that the growth of concentration of carbon vacancies increases the magnetic moment per Fe atom in the cementite lattice.…”

“…In the course of plastic deformation of patented wire, complex physical processes take place in both ferrite and cementite components of pearlite. There are papers that report the formation of the cellular substructure [2][3][4][5][6][7][8][9][10][11][12][13] in ferrite plates; changes in the chemical composition of cementite upon deformation [14][15][16][17][18][19][20][21][22] and, consequently, in its physical-mechanical properties; the formation of metastable ferric carbide with a higher carbon content [15,16,23,24]; and a partial dissociation of cementite at large deformations. All these processes differently affect the ability of a patented wire to be deformed and lose plasticity, i.e., the phenomenon of "overhardening.…”