Analysis of precipitation in Fe-rich Fe-Ni-Al alloys by diffusion couples

The precipitation process of the beta' phase was studied in Fe-rich Fe-Ni-Al alloys using a Fe-25 at%Ni-25 at%Al alloy and pure Fe diffusion couple. The formed concentration gradient allowed to study the aging process at 900 degrees C in Fe-Ni-Al alloys with Al and Ni contents up to about 23 at%. The morphology of precipitates was rounded cuboids and it changed to elongated plates as the aging progressed the precipitate coarsening kinetics followed the modified LSW theories. The precipitate coarsening resistance decrease with the increase in the volume fraction of precipitates. In order to evaluate the effect of the precipitation process on the mechanical properties of the alloy tested, micro Vickers hardness was measured, showing an increase of hardness on the Al and Ni content increased. (C) 2012 Elsevier B.V. All rights reserved.