An FEGSTEM Study of Grain Boundary Segregation of Phosphorus during Quenching in a 2.25Cr-1Mo Steel

摘要

Quenching-induced phosphorus segregation to prior austenite grain boundaries in a 0.077 wt pct P-doped 2.25Cr1Mo steel is examined using field emission gun scanning transmission electron microscopy (FEGSTEM). A phosphorus level of around 1.56 at. pct is observed for the water-quenched sample. In recognition of insufficiently high spatial resolution of the technique for grain boundary composition analysis, the measured results are corrected by an analytical convolution method. The corrected phosphorus segregation level may be up to about 4.7 at. pct. The quenchinginduced phosphorus segregation is nonequilibrium segregation and the migration of vacancy-phosphorus complexes plays an important role in the kinetic process. For such a reason, the mechanism for migration of the complexes is discussed in some detail.