Development of L1_2-ordered Ni_3(Al,Ti)-strengthened alumina-forming austenitic stainless steel alloys

摘要

The stability of coherent L1_2-ordered Ni3(Al,Ti) intermetallic precipitates was studied in Fe-14Cr-32Ni-3Nb-(3-4)Al-(l-3)Ti (wt.%) based alumina-forming austenitic stainless alloys. Computational thermodynamics predicted the formation of multi-intermetallic phases, including L1_2 and β-NiAl (B2), in an austenite matrix below ～900 °C. Microstructure characterization revealed a significant stabilization of the L1_2 phase by Zr addition, with the amount of L1_2 increasing with increasing Ti addition. However, the Ti addition also degraded the oxidation resistance. Further additions of C and B successfully improved both creep and oxidation properties.