Evaluation of the Mechanisms of Compression Hardening of Rail Steel

Methods of modern physical materials science are used to study the evolution of structural-phase states and dislocation substructure of rail steel under uniaxial compression deformation up to 50%. The revealed fragmentation of pearlite grains becomes more expressed with increasing deformation, and the fragmentation of cementite plates with the fragment size of 15–20 nm weakly depends on the degree of deformation. The change in the scalar and excess dislocation density with increasing deformation is analyzed. Sources of internal stress fields are identified and classified. The data obtained formed the basis for a quantitative analysis of the mechanisms of hardening of rail steel at degrees of compression deformation of 15, 30, and 50%. The contributions to strengthening caused by friction of the matrix lattice, dislocation substructure, fragment boundaries, carbide particles, internal stress fields, solid-solution strengthening, and the pearlite component of the steel structure are estimated. The primary mechanism of metal hardening at the deformation of 50% is hardening by incoherent particles and elastic internal stress fields. Using the additivity principle, which assumes the independent action of each of the hardening mechanisms, the dependence of the total yield strength of rail steel on the degree of compressive deformation is estimated.