Quenching and tempering-induced molybdenum segregation to grain boundariesin a 2.25Cr-1Mo steel

Molybdenum is one of the major alloying elements in low-alloy structural st eels and is beneficial for mitigating temper embrittlement. Enhancement of the grain boundary cohesion by molybdenum segregation is one of the mechani sms for molybdenum to alleviate the temper embrittlement. To understand cle arly the segregation behaviour of molybdenum in low-alloy structural steels , examination of molybdenum grain boundary segregation during quenching and tempering in a 2.25Cr-1Mo steel is conducted experimentally by virtue of f ield emission gun scanning transmission electron microscopy. There is some molybdenum segregation during quenching. Supersaturated vacancies created b y quenching play a certain role in the segregation. Combined equilibrium an d non-equilibrium segregation of molybdenum is the nature of segregation in the tempered steels. (C) 2000 Elsevier Science S.A. All rights reserved.