Mechanical properties and oxidation behaviour of two-phase iron aluminium alloys with Zr(Fe,Al) 2 Laves phase or Zr(Fe,Al) 12 τ 1 phase

Abstract

Two-phase Fe-rich Fe–Al–Zr alloys have been prepared consisting of binary Fe–Al with a very low solubility for Zr and the ternary Laves phase Zr(Fe,Al) 2 or τ 1 phase Zr(Fe,Al) 12. Yield stress, flexural fracture strain, and oxidation behaviour of these alloys have been studied in the temperature range between room temperature and 1200 °C. Both the Laves phase and the τ 1 phase act as strengthening phases increasing significantly the yield stress as well as the brittle-to-ductile transition temperature. Alloys containing disordered A2+ ordered D0 3 Fe–Al show strongly increased yield stresses compared to alloys with only A2 or D0 3 Fe–Al. The binary and ternary alloys with about 40at.% Al and 0 or 0.8at.% Zr show the effect of vacancy hardening at low temperatures which can be eliminated by heat treatments at 400 °C. At higher Zr contents this effect is lost and instead an increase of low-temperature strength is observed after the heat treatment. The increase of the high-temperature yield strength of Fe-40at.% Al by adding Zr is much stronger than by other ternary additions such as Ti, Nb, or Mo. Tests on the oxidation resistance at temperatures up to 1200 °C indicate a detrimental effect of Zr already for additions of 0.1at.%.