Effect of reverse-aging treatment on the microstructure and mechanical properties of Nimonic alloys

Abstract

Tensile (at 295 and 1023 K) and stress rupture (at 1023 K and 315 MPa, at 1143 K and 145 MPa, and at 1088 K and 180 MPa) properties of Nimonic 90 and Nimonic 80A alloys have been measured following regular and reverse-aging heat treatments. The reverse-aging heat treatment (1353 K for 8 h, air cool + 973 K for 12 h, air cool + 1073 K for 2 h, air cool) gave significantly improved tensile strengths, tensile ductility and stress rupture lives for both the alloys compared with the corresponding values obtained with the conventional heat treatment (1353 K for 8 h, air cool + 973 K for 16 h, air cool). The improved tensile properties are rationalized in terms of microstructure, slip character and fracture mode.