Mn-Stabilized Austenitic Steel Strengthened By Nano-Scale Beta-Nial (B2), Fcc-Cu, And Carbides Via Icme Design

An integrated computational materials engineering (ICME) approach was used to design a fully Austenitic, Mn-stabilized steel strengthened by three nano-scale precipitate phases: beta-NiAl, FCC-Cu, and M23C6 carbides. Thermo-Cale was used to predict the effects of Ni, Al, and Cu additions on phase stability in a Fe-17.7Mn-4.7Cr-0.48C (wt.%) base Austenitic composition. These predictions were verified experimentally by (1) synthesizing alloys of this Austenitic base alloy modified with Cu, Ni+Al, or Cu+Ni+Al, (2) measuring the mechanical properties by microindentation, and (3) characterizing the nano-scale microstructures by atom probe tomography (APT). After ageing at 580 degrees C, selected based on Thermo-Cale modeling, only minor hardening was observed in samples modified with either Cu or Ni+Al. However, the alloy with combined additions of Cu together with Ni+Al exhibited significant hardening (490 HV, corresponding to an estimated sigma(gamma) approximate to 1200 MPa), which was attributed to the formation of FCC-Cu and beta-NiAl nano-precipitates. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.