Thermal stability of nano-structured ferritic alloy

The excellent tensile and creep strength and the potential for managing radiation damage make nano-structured ferritic alloys (NFAs) promising candidates for high-temperature applications in spallation proton, advanced fission and fusion neutron environments. The thermal stability of NFAs is critical for such applications, hence, this has been investigated in a series of aging experiments on MA957 at 900 degrees C, 950 degrees C and 1000 degrees C for times up to 3000 h. Optical and transmission electron microscopy (TEM) studies showed the fine scale grain and dislocation structures are stable up to 1000 degrees C. TEM and small angle neutron scattering (SANS) showed that the nm-scale solute cluster-oxide features (NFs), that are a primary source of the high strength of NFAs, were stable at 900 degrees C and coarsened only slightly at 950 degrees C and 1000 degrees C. Porosity that developed during high-temperature aging was minimal at 900 degrees C and modest at 950 degrees C, but was much larger after 1000 degrees C. Microhardness was basically unchanged after the 900 degrees C aging, and decreased only slightly (<= 3%) after aging at 950 degrees C and 1000 degrees C. (c) 2008 Elsevier B.V. All rights reserved.