The dependence of the flow stress of armco iron on strain history

Abstract

This paper presents experimental results concerning the influence of strain history on the yield stress of Armco iron. Uniaxial tensile tests were performed over the temperature range of 213 to 1023 K and the strain-rate range of ϵ ̇ = 2.77 × 10 −5 s −1 to ϵ ̇ = 2.77 × 10 −2 s −1 To obtain qualitative information concerning the structure of the deformed material, additionally observations were made using a transmission electron microscope. Experimental results show that the value of the flow stress depends not only on strain ϵ, strain rate ·/ϵ and temperature T, but also on the history of deformation and the temperature and time-dependent thermally activated phenomena of ageing and recovery. These phenomena cause changes in structure, and therefore also in the plastic properties of material. On the basis of experimental results, an attempt has been made to separate the effects of deformation from those of the accompanying phenomena of ageing and recovery, depending on the temperature and duration of the processes.