Influence of temperature and post weld heat treatment on tensile stress-strain and work hardening behaviour of modified 9Cr-1Mo steel

True stress (σ)-true plastic strain (ε) and work hardening behaviour of modified 9Cr-1Mo steel in normalised and tempered (N + T), and three different post weld heat treatment (PWHT) conditions have been examined in the framework of Hollomon, Ludwigson and Voce relationships in the temperature range 300-873 K. The analysis indicated that the σ-ε behaviour is described accurately by the combination of Ludwigson and Hollomon equations. Alternatively, Voce equation provides an adequate description of σ-ε behaviour in the range 300-873 K. The variations of work hardening parameters associated with Ludwigson/Hollomon and Voce relationships with temperature exhibited three distinct temperature regimes displaying signatures of dynamic strain ageing at intermediate temperatures and dominance of dynamic recovery at high temperatures. The influence of additional PWHTs is discussed in terms of the systematic variations in flow and work hardening parameters due to microstructural softening with increasing PWHT temperature observed for the steel.