On the onset of necking instability in tempered martensitic 9% Cr steels

Abstract

Considère criterion accounting for necking instability has been examined in terms of dislocation density based approach for tempered martensitic 9% Cr steels. The critical dislocation density as well as the critical strain at which instability sets-in has been predicted from the dislocation dynamics approach. The parameters associated with the approach such as mean free path of dislocations and dynamic recovery have been the key for developing microstructural based necking instability criterion. The interrelationship between true uniform plastic strain and dynamic recovery parameter has been established from the present formulation for tempered martensitic 9% Cr steels. The increase in dynamic recovery with decreasing mean free path and increasing temperature strongly influences the work hardening ability of tempered martensitic 9% Cr steels.