New developed quaternary refractory superalloys

The novel idea for designing quaternary superalloys by two kinds of binary alloys with coherent structure was applied to Ir-Nb- Ni-Al superalloys. Eig ht alloys were prepared by combining two sorts of binary alloys, Ir-Nb and Ni-Al, in different proportions. The effects of the mole fraction of Ir-bas ed alloy or the Ll(2) alloy on the microstructure and the 0.2% flow stress of quaternary alloys were investigated. Two sorts of coherent structure, fc c/Ll(2)-Ir3Nb and fcc/Ll(2)-Ni3Al, were observed in the quaternary superall oys. The new developed quaternary Ir-based superalloys are of the advantage s of Ir-based alloys and Ni-based superalloys. The 0.2% flow stress of Ir-N b-Ni-Al at 1200 degrees C could reach up to 350 MPa and the compressive str ains were improved greatly compared with Ir-based alloys. (C) 2000 Elsevier Science Ltd. All rights reserved.