Transformation to pearlite from work-hardened austenite.

Abstract

The effects of austenite deformation conducted below the recrystallization temperature on the subsequent isothermal transformation to pearlite in an eutectoid steel (SKD 6, H11) were quantitatively studied. The plastic deformation in the austenite condition was observed to lead to marked acceleration of austenite→pearlite transformation. This acceleration was found to be mostly caused by the increase in the nucleation rate but not by the increase in the growth rate.The increase in the nucleation rate per unit volume of specimen was attributed (1) to the increase in the austenite grain surface by the elongation of grains, (2) to the increase in the nucleation rate per se per unit area of grain surface, and (3) to the formation of additional nucleation sites such as annealing twin boundaries, deformation bands, etc. Among these the increase in the nucleation rate per se per unit area of grain surface was found to have the largest effect on the acceleration of transformation by deformation in the steel studied.The effects of rolling reduction and austenite grain size on the acceleration mechanism of transformation were discussed based on the derived kinetic equation.