Evolution of metastable phases during crystallization of pulsed laser deposited amorphous Al–Fe films

Abstract

Amorphous thin films of different Al–Fe compositions were produced by plasma/vapor quenching during pulsed laser deposition. The chosen compositions Al72Fe28, Al40Fe60, and Al18Fe82 correspond to Al5Fe2 and B2-ordered AlFe intermetallic compounds and α–Fe solid solution, respectively. The films contained fine clusters that increased with iron content. The sequences of phase evolution observed in the heating stage transmission electron microscopy studies of the pulsed laser ablation deposited films of Al72Fe28, Al40Fe60, and Al18Fe82 compositions showed evidence of composition partitioning during crystallization for films of all three compositions. This composition partitioning, in turn, resulted in the evolution of phases of compositions richer in Fe, as well as richer in Al, compared to the overall film composition in each case. The evidence of Fe-rich phases was the B2 phase in Al72Fe28 film, the L12- and DO3-ordered phases in Al40Fe60 film, and the hexagonal ε–Fe in the case of the Al18Fe82 film. On the other hand, the Al-rich phases were Al13Fe4 for both Al72Fe28 and Al40Fe60 films and DO3 and Al5Fe2 phases in the case of Al18Fe82 film. We believe that this tendency of composition partitioning during crystallization from amorphous phase is a consequence of the tendency of clustering of the Fe atoms in the amorphous phase during nucleation. The body-centered cubic phase has a nucleation advantage over other metastable phases for all three compositions. The amorphization of Al18Fe82 composition and the evolution of L12 and ε–Fe phases in the Al–Fe system were new observations of this work.

On the microstructure and the origin of intermetallic phase seams in magnetic pulse welding of aluminum and steel

“…This is a strong indication for the presence of an amorphous component within this thin interlayer. Amorphous phases consisting only of iron an aluminum are normally only achieved in vapor quenching processes like pulsed laser deposition, where the precipitation of the evaporated material on a substrate is an extremely fast process [14]. Alternatively, meltquenching processes require the presence of significant amounts of another alloying element besides iron (e. g. boron [15] or cerium [16]) to obtain an amorphous aluminum matrix.…”

Microstructural evolution and metastable phase formation in laser ablation-deposited films of Fe-rich Fe–Ge intermetallic compounds

“…Pulsed laser ablation (PLD) is a versatile technique for depositing thin film of metals, alloys and ceramics [1][2][3][4][5][6][7][8]. The process primarily involves quenching of matter from vapour and plasma on a substrate by striking a high-power pulsed laser beam on a target [9].…”