High-strength steels hardened mainly by nanoscale NiAl precipitates

NiAl-strengthened high-strength steels usually have high Ni and Al contents in order to form hardening particles. Here, several new low-Ni steels are reported, which achieve a combination of relatively low cost, high strength and good ductility mainly through the precipitation of high number densities of nanoscale NiAl precipitates as characterized by atom probe tomography. The precipitation parameters are tuned by optimizing both alloy compositions and heat-treatment parameters. The strengthening effects of nanoscale NiAl and Mo/W-rich carbides are quantitatively analyzed and assessed.