MICROSTRUCTURAL EVOLUTION AND OXIDATION BEHAVIOR OF Fe-4Cr-6Ti FERRITIC ALLOY WITH Fe2Ti LAVES PHASE PRECIPITATES

Abstract

The microstructural properties and hardness of a model ternary Fe-4Cr-6Ti ferritic alloy aged at 800??C for 8, 16 and 24 h are investigated in detail. Fine Fe2Ti Laves phase particles precipitate in the a-Fe (ferrite) matrix phase after solutionizing and subsequent aging treatments. The size and amount of Fe2Ti precipitates gradually increase with increasing aging time. The magnetic measurements of the aged samples confirm the variations in the microstructural properties including the volume fraction of the constituent phases, and Ti content of the a-Fe matrix phase. The mean Vickers microhardness value also increases from 203.5 to 238.4 with increasing aging time from 8 to 24 h. In addition, the cyclic oxidation behavior of 24 h aged sample, which contains maximum amount of Fe2Ti precipitates, is also investigated in detail. X-ray diffraction analysis reveals that scale product is a-Fe2O3 (hematite). Significant scale spallation and void formation is observed on the surfaces of 24 h aged Fe-4Cr-6Ti sample oxidized at 500??C.