The effect of annealing on NiAlFe B2 compounds

Microalloying effects on the microstructure and kinetics of nanoscale precipitation in Ni–Al–Fe alloy

“…This confirms that fine precipitates appearing as dark regions in superlattice dark field image (Fig. 10(c)) formed using 100 reflection are coherent disordered bcc a-Fe precipitates inside an ordered matrix [21,22,38].…”

“…This could be attributed to the precipitation of second phase particles possessing ferromagnetism. The precipitating ferromagnetic phase is an Fe-rich bcc formed within the miscibility gap between ordered (B2) and disordered bcc a-Fe phases [23,35,36] which strengthens the alloy via precipitation hardening through dislocation pinning effect [21,22,37]. Annealing at 873 K causes softening of the b-phase by coarsening of a-phase precipitates, and, annealing at 1073 K decreases the microhardness to values similar to those in the as-cast state which can be explained by the dissolution of precipitates above the miscibility gap.…”

Kinetics of nanoscale precipitation in Ni–Fe–Al alloys: A magnetic monitoring approach

“…It can be stated that these precipitates attained their optimum size because an increase in the annealing temperature to 873 K caused drops in hardness by ∼10-15%. This could be related with the coarser microstructure formed at high temperatures [7] in accordance with the significant increases in rates of magnetization during isothermal scans at such high temperatures in VSM. In this respect, it is clear from Fig.…”

“…On the other hand, the improvement of room temperature ductility and high temperature strength requires further attention for utilization in demanding applications. In this respect, the incorporation of Fe into the NiAl system has been shown to remarkably modify the structural properties [4][5][6] and promote precipitation of a fine body centered cubic (BCC) ␣-phase, which strengthens the alloy [7][8][9]. Although the ␣-precipitates are softer than the BCC ␤-matrix, they induce changes in the slip system and strengthen the alloys via precipitation hardening through a dislocation pinning effect [7,10].…”