The effect of Zr addition on the structure and high temperature strength of Fe-30 at.% Al type alloys

The structure of four Fe–30Al alloys with different contents of Zr has been studied. Light optical microscopy (LOM), scanning electron microscopy (SEM) with EDX module, measurement of microhardness as well as X-ray diffraction (XRD) was used to determine the structure and phase composition. Addition of Zr to Fe–30Al leads, in the cast state, to the formation of a Fe–Al matrix with a hard lamellar eutectic skeleton. The eutectic is composed of thin lamellae of λ1-Laves phase Zr(Fe,Al)2 and Fe–Al (B2/D03). Annealing at 1000 °C for 200 h results in the formation of the equilibrium phase τ1 Zr(Fe,Al)12. The presence of these phases in the matrix leads to increase of high temperature yield stress and strength.

The structure of the as-cast alloy 30Al_5Zr the same alloy annealed 1000 °C/200 h. Fe–Al + eutectic (λ1 + Fe–Al) Fe–Al + λ1 + τ1.Figure optionsDownload as PowerPoint slideHighlights
► The phase composition of cast and annealed Fe–30Al-0.4÷5.2Zr (at.%) alloys.
► Hardening after H.T. annealing is connected with hard τ1-phase.
► The strength of the tested alloy is given by the composite character of the alloy.