Growth kinetics of β'precipitation in a ferritic matrix during isothermal aging of cu-containing Fe-10at.%Ni-15at.%Al alloys

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.