A study of the relation between grain boundary type and sensitisation in a partially-sensitised AISI 304 stainless steel using electron back-scattering patterns

Electron backscattering (ebs) patterns were used to measure the orientations of grains in lightly sensitized 304. The misorientations across grain boundaries were calculated, and correlated with the extent of attack on the boundaries by an electrochemical test designed to reveal sensitization due to Cr depletion. Low-angle boundaries were found to be unsensitized. Twin boundaries were either unsensitized or partly sensitized, probably reflecting the difference between coherent and incoherent twin boundaries. The majority of general, high angle boundaries were found to be completely sensitized, but a significant fraction were unsensitized or only partly sensitized, showing that a variation in susceptibility to sensitization exists even among general, high angle boundaries. High angle boundaries (other than twins) with coincident site lattice misorientations were distinguishable from general high angle boundaries in this respect. The ebs technique is a rapid and useful method of measuring grain boundary misorientations.