High-temperature creep properties of Fe–Al alloys modified by Zr

Abstract

Abstract Two Fe – Al alloys with Zr additions were prepared by vacuum induction melting and rolling at 1200 °C: a disordered (ferrite – A2) and a D03-ordered one. The data are compared to a similar Fe3Al-based alloy with lower Zr content investigated earlier. Tensile and creep tests were performed at 600, 700, and 800 °C, where the disordered alloy maintains its A2 structure, and D03-ordered alloys are transformed to B2-ordered structure. Transmission electron microscopy of the alloys crept at 600 °C showed precipitation of fine particles on dislocations, subgrain boundaries and also in the matrix. Coarsening of these particles during creep at 800 °C takes place. The particles in Fe3Al-based alloys are identified mostly as zirconium carbides, whereas (Fe, Al)2Zr precipitates were observed in the ferritic alloy. The increase of Zr content from 0.25 to 0.6 at.% does not have a significant effect on the high temperature (HT) mechanical properties of the Fe3Al-type aluminide, because both alloys contain the same amount of carbon. In consequence no additional volume fraction of ZrC particles could be formed. The creep resistance of the ferritic alloy is considerably lower, but this material can easily be rolled to prepare sheets for HT corrosion protection.