Thermal stability of nanocrystalline Fe-10 wt.% Al produced by cryogenic mechanical alloying

Abstract

Abstract Nanocrystalline Fe-10 wt.% Al material is synthesized using cryogenic high energy ball milling (cryomilling). The resultant powders are compacted in a rigid die at 350 MPa and 823 K in an argon atmosphere. The grain size of the powder compacts, determined using transmission electron microscopy, is found to be 11 ±5 nm. Subsequent heat treatment for 1 hour at temperatures of 1073 K and 1223 K reveals that fine grain sizes of 13 ± 6 nm and 16 ± 7 nm, respectively, are maintained. Only when the heat treatment temperature is increased to 1373 K, or over 75% of the melting point of Fe, do relatively large grainsform, approaching 100 nm. This level of thermal stability is shown to exceed that of pure Fe processed under identical conditions, by a significant margin. The present results indicate that the increase in thermal stability may originate from the pinning effect offine dispersoids formed during cryomilling and subsequent heat treatment.