Effect of alloying elements on age hardening and coarsening of β′ precipitates in isothermally aged Fe–Ni–Al based alloys

Abstract

Precipitation and coarsening processes of Fe-10 at.% Ni-15 at.% Al, Fe-10 at.% Ni-15 at.% Al-1 at.% Cr, and Fe-10 at.% Ni-15 at.% Al-1 at.% Cu alloys were carried out during isothermal aging at temperatures of 750, 850, and 950 °C using experimental and numerical analysis methods. Thermo-Calc numerical results indicated that the Cu addition promoted higher volume fraction of β′ precipitates, which caused better response to the age hardening than the other two alloys. The coarsening resistance was also detected to be higher for the Cu-containing alloy in comparison with the other alloys because of its lower solubility and volume diffusion in the ferrite matrix. The Cu and Cr alloying elements were observed to be located in the precipitate and matrix, respectively, according to their expected thermodynamic behavior.