Structure and Properties of the Eutectoid Steel U8 after High-Temperature Deformation: III. Deformation at Temperatures below the Equilibrium Temperature of Eutectoid Transformation

摘要

Structure of the carbon eutectoid steel U8 has been studied after hot deformation by torsion in a temperature range of 650-700 de C using electron microscopy (g center dot b technique). It has been shown for the first time that dislocations that are present in austenite can be inherited by both structural constituents of pearlite upon phase transformation occurring simultaneously with deformation. It has been shown that the superimposition of the processes of deformation and phase transformation leads to a fragmentation of cementite plates and the formation of a polygonal structure in ferrite simultaneously with the formation of pearlite colonies. In samples with a mixed structure (pearlite + bainite-martensite regions), there are formed several morphological types of the products of shear transformation: upper bainite, twinned and lath martensite, and coarse martensite plates with a clearly pronounced midrib. Inside the coarse martensite crystals and at the matrix-twin boundaries, finely disperse carbide particles precipitate.