Phase Structure and High-Temperature Mechanical Properties of Two-Phase Fe-25Al-xZr Alloys Compared to Three-Phase Fe-30Al-xZr Alloys

The structure and high-temperature mechanical properties of Fe-30 at. pct Al and Fe-25 at. pct Al alloys with various Zr contents are compared. The scanning electron microscope images in chemical contrast mode (R-BSE) as well as EDS, EBSD, and X-ray diffraction were used to determine the structure and phase composition. The as-cast alloys (both Fe-30Al and Fe-25Al) were observed to be two-phase DO3/B2 + Laves phase lambda(1) (Fe,Al)(2)Zr alloys with typical fine lamellar eutectic areas. During the heat treatment of the Fe-25Al alloys, their structure transformed from a DO3/B2 matrix with fine lamellar eutectic into lambda(1) globular particles situated in a DO3/B2 matrix. The same structure of Fe-30Al alloys decomposed into three phases: lambda(1) and tau(1) Zr(Fe,Al)(12) particles in a DO3/B2 matrix. The hardening in both groups of alloys (Fe-25Al and Fe-30Al) due to the presence of Zr-containing lambda(1) and tau(1) phases is compared.