Sensitization behavior of thermomechanically processed AISI304L stainless steel was investigated. The mechanical processing was carried out at deformations of 30 to 90% (reduction in thickness), and annealed subsequently at 800 to 950C for 0.25 to 1h. Stainless steel was then sensitized at 675C both for short (2h) and long (53h) durations. Thus treated specimens were characterized for grain boundary character distribution, grain size, and degree of sensitization. The increase in annealing temperature and time following mechanical processing showed an increase in grain size (up to 37μm) and in the degree of sensitization. The fraction of coincident site lattice boundaries (Σ3 to Σ29) was also noticed to increase with the annealing temperature, which implied that an increasing fraction of low energy boundaries did not cause a decrease in the degree of sensitization. The grain size through its effect on grain boundary surface area and the effective grain boundary energy correlated well with the extent of sensitization. Grain growth reduced the grain boundary surface area and the effective grain boundary energy as well, which, in turn, enhanced the degree of sensitization. A critical grain size (∼<16μm), below which, and correspondingly a critical effective grain boundary energy (∼>0.05), above which, sensitization reduced to insignificant levels was observed.

Modification of Sensitization Resistance of AISI 304L Stainless Steel through Changes in Grain Size and Grain Boundary Character Distributions. R.Singh, S.G.Chowdhury, I.Chattoraj: Metallurgical and Materials Transactions A, 2008, 39[10], 2504-12