Influence of nanometric oxide dispersion on creep resistance of ODS FeAl prepared from prealloyed powders

• Published in: Scripta materialia Vol. 34; no. 5; pp. 815 - 823
• Main Authors: Wolski, K., Thévenot, F., Le Coze, J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.1996
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/1359-6462(95)00589-7

Intermetallic Fe-40 at.% Al is characterized by excellent oxidation and corrosion resistance at high temperatures, low cost of raw materials, relatively low density (6.0 g/cm exp 3 ) and significant ductility at room temperature. The ductility depends on composition, boron addition, environmental effect and in optimized conditions of processing was measured to be at least 6%. One of the limitations of this material is its insufficient creep strength at approx700 deg C, the temperature for potential applications instead of stainless steels or standard superalloys. The creep strength can be improved by introducing oxides into FeAl matrix, however, very fine dispersion ( < 50 nm) is needed to make the increase in the creep strength significant. One of the methods to obtain this kind of material is in situ formation of dispersion during attrition of prealloyed FeAl powders. Subsequent sintering or hot extrusion results in the transformation of the oxidation products into nanometer oxides with homogeneous distribution. In extruded conditions, therefore after recrystallization of the matrix, this ceramic dispersion strongly limits the grain growth of the matrix. Decreasing the grain size of the matrix is beneficial for ductility, as demonstrated for NiAl intermetallic. This beneficial effect has also been observed in ODS FeAl. This paper is focused on the rheological properties of FeAl prepared by attrition coupled with in situ formation of the dispersion and subsequent sintering. Critical steps of processing, leading to the formation of the nanosized ceramic dispersion are also addressed, however, a detailed description of the type of oxides formed is presented elsewhere. This paper describes a part of a larger study aimed at the improvement of the creep strength of FeAl by dispersion of oxides.