Tailoring Dynamic Recrystallization in Ni- and Fe-Base High Temperature Alloys

Abstract

Theory for describing the conditions leading to dynamic recrystallization in FCC metals is introduced. The approach also describes stress-strain curves when this process occurs, and is unique in incorporating the effects of strain rate and temperature employing only physical parameters as input. The novelty of the approach stems from incorporating an incubation period in the equations describing the progress of dislocation density with strain; beyond such incubation dislocation free grains form. The energy barrier to ignite grain growth is expressed as a function of the strain energy stored in the material and a statistical entropy contribution due to the degrees of freedom available to a dislocation for annihilation. The incubation strain is obtained by performing an energy balance between the stored energy on the subgrain boundaries, the slip energy for boundary migration and the interfacial energy required for grain nucleation. The application of this work to Fe and Ni multicomponent alloys has lead to transition maps in temperature-strain rate space indicating the conditions for dynamic recrystallization occurrence.