Thermal Densification of Austenitic Stainless Steel

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Abstract
Densification occurs during the aging of austenitic stainless steels. This study was conducted to determine the extent of densification during thermal aging of AISI Type 316 stainless steel. This objective was accomplished through both length change measurements and bulk density measurements on Type 316 stainless-steel tubing before and after aging treatments at 1200°F for aging times up to 1000 h. Various cold work levels, from 0 to 20%, were investigated. In all cases the tubes were found to shrink, the shrinkage increasing with cold-work level and aging time with a maximum change of −0.06% ΔL/L. A comparison of the bulk density and length change measurements indicates that within the experimental accuracy the densification phenomena are isotropic. Irradiation-induced creep and swelling in austenitic stainless steels have been a source of major concern in the development of LMFBRs. The densification or shrinkage phenomena influence measurements particularly for low values of strain and/or swelling. It is therefore important to take the densification phenomena into account when extrapolating low fluence data on swelling and creep.