Compression creep studies of mechanically alloyed nanostructured Fe-12Cr-2W-0.25Y₂O₃ ODS alloy

Abstract

Nanocrystalline Fe-12Cr-2W (wt.%) and oxide dispersion strengthened (ODS) Fe-12Cr-2W-0.25 Y₂O₃ (wt. %) alloy powders were produced through mechanical alloying in a high energy planetary ball mill. Microhardness studies on individual milled powder particles revealed a clear increase of hardness for the Yttria containing alloy, thus, proving the ODS effect to be operative in the powders. Consolidation was carried out in a uniaxial hot press at 900°C with a pressure of 200 MPa. TEM and XRD analyses consistently revealed the nanocrystalline grain size before (12 to 30 nm) and after consolidation (120 nm), respectively. Compression creep studies in a temperature range between 800 and 1000°C revealed that diffusional creep is obviously suppressed in these materials. However, the creep resistance of the ODS ferritic steel is only marginally higher than its base alloy and both alloys are by far less creep resistant than that of a ferritic steel of comparable baseline composition strengthened by complex and exceptionally thermally stable Ti-Y-O nanoclusters [1]. Both differences can be rationalized by the instability of the microstructure leading to significant particle and grain growth after creep testing.