THE KINETICS OF FORMATION AND GROWTH OF TIC PRECIPITATES IN TI-MODIFIED STAINLESS-STEEL STUDIED BY POSITRON-ANNIHILATION SPECTROSCOPY

The formation and growth of TiC precipitates in Ti-modified austenitic stainless steel (D-9 alloy) is monitored by positron lifetime spectro scopy. From isochronal annealing studies various recovery stages are i dentified. TIC precipitates are found to be more stable in 20% cold wo rked alloy than in a 17.5% cold worked sample. From the isothermal ann ealing studies, it is found that TIC precipitation is controlled by di slocations. The limited temperature dependence of dislocation controll ed TIC precipitation is governed by an apparent activation energy of 1 .6 eV. In 20% cold worked alloy, TiC precipitates are found to be stab le against growth even after 1000 h of annealing at 923 K. For higher annealing temperatures, TiC precipitate coarsening occurs due to recry stallisation, (C) 1998 Elsevier Science B.V. All rights reserved.