Growth Kinetics of β´Precipitation in a Ferritic Matrix During Isothermal Aging of Cu-containing Fe-10at.%Ni-15at.%Al alloys

Abstract A precipitation study was carried out during the isothermal aging at 850 °C for Fe-10at.%Ni-15at.%Al, Fe-10at.%Ni-15at.%Al-2.5at.%Cu and Fe-10at.%Ni-15at.%Al-5at.%Cu alloys. The experimental, Calphad, and Kinetic/Precipitation calculated results indicated that the Cu-addition to the ternary alloy promoted a higher volume fraction of β´precipitates, which caused a better aging response for the Cu-containing alloys. The coarsening resistance was the highest for the 2.5 at. % Cu-containing alloy, compared to the ternary alloy because of its lower interfacial free energy, 0.009 Jm-2, between the precipitate and the matrix. The Cu alloying element was located mainly in the β´ precipitate according to its expected thermodynamic behavior, and it caused an atomic relation of Ni to Al close to that of NiAl intermetallic compound for the β´phase. A content of 5 at. % Cu in the ternary alloy promoted higher interfacial energy, 0.04 Jm-2, and thus the fastest coarsening process.