Microstructure and mechanical property evolution of an AFA alloy with simple composition design during ageing at 700 °C

The influence of Y and Nb addition on the corrosion resistance of Fe-Cr-Al-Ni model alloys exposed to oxygen-containing molten Pb

“…The co-precipitation of B2-NiAl and Fe2Nb Laves phases has been observed previously in AFA alloys microstructure [20,26,39]. One possible explanation is that the precipitation of Fe2Nb Laves phase leads to the occurrence of Fe-depleted regions, in which the formation of B2-NiAl phase and of Cr-rich ferrite is triggered in adjacent location, at lower temperature than in the Nb-free alloys.…”

“…Alumina forming austenitic (AFA) steels, initially developed as structural materials for energy related applications, have shown excellent corrosion resistance and mechanical properties [17][18][19][20][21]. By alloying with low amount of Al (<5 wt.%), AFA steels are able to form an external alumina scale in oxidizing environments at 600-900 °C [17][18].…”

“…Y and Nb have significant positive influence on the corrosion resistance and the phase composition of the alloys.small amounts of other elements can also be added to optimize the properties (e.g. mechanical, corrosion resistance, structure stability) for applications, for instance, stabilize the austenite structure (C, Cu, Mn), precipitate the minor secondary phases (Nb, Ti), increase scale adherence (Y), strengthen the austenite (W, Mo) and its grain boundaries (B) [17][18][19][20][21][22][23][24][25][26][27][28][29].Recent research results indicate that alumina forming austenitic (AFA) model alloys with the chemical composition formula Fe-(20-29)Ni-(15.2-16.5)Cr-(2.3-4.3)Al (wt.%) are able to form alumina-rich protective scale during exposure to oxygen-containing molten Pb at 550-600 °C for 1000 h and to preserve the austenitic matrix [9][10]. The passive and continuous oxide scales, grown on alloy surfaces, are based on two corundum-type crystalline structures, Cr2O3 and Al2O3-Cr2O3 solid solutions.…”

“…small amounts of other elements can also be added to optimize the properties (e.g. mechanical, corrosion resistance, structure stability) for applications, for instance, stabilize the austenite structure (C, Cu, Mn), precipitate the minor secondary phases (Nb, Ti), increase scale adherence (Y), strengthen the austenite (W, Mo) and its grain boundaries (B) [17][18][19][20][21][22][23][24][25][26][27][28][29].…”

Research Progress of Alumina-Forming Austenitic Stainless Steels: A Review

“…Some studies [ 22 , 43 , 66 , 67 ] have found that B2-NiAl has a ductile–brittle transition temperature (DBTT) that is related to the matrix composition, and generally ranges from 500 °C to 800 °C. If the temperature is higher than the DBTT, it would lose its strength effect.…”