HOT DEFORMATION OF AUSTENITE IN A PLAIN CARBON STEEL.

Abstract

High temperature tensile deformation of a 0. 16% C steel was studied over a wide range of strain rates from 18 to 2. 73 multiplied by 10** minus **5 sec** minus **1 in the austenite range. From metallographic observations and flow stress measurements it was revealed that the first flow stress maximum, delta //M, the shape of the delta - epsilon curves, and the deformed structure in high strains were unique functions of the Zener-Hollomon parameter, Z, which was calculated on an activation energy for deformation (68. 5 kcal/mol). The distinct structural changes occurred in the initial hardening stage below the strain at delta //M, and the gamma grain structures for high strains were of a mixture of fine grains and comparatively coarse grains, and the grain boundaries of the latter were wavy on the whole regardless of Z. Deformation was controlled by the dynamic recrystallization process assisted by the migration of vacancies.