Phase transformations in alloys of the Fe–V system

Diffusive phase transformations: Example of Fe–M alloys

“…Contrary to the theoretical conclusions, some experimental data obtained on the Fe-Cr [5], Fe-Co [6], Fe-V [7], Fe-W [8], Fe-Ti [9] systems show that the type of the chemical interactions in alloys depends on quite other causes. We can demonstrate this with an example of the Fe 50 Co 50 alloy in which B2 ordering takes place below 730 • C and phase separation is observed above 730 • C [6].…”

“…However, as experimental data show, this happened not always. If thephase in the Fe 50 V 50 alloy is really formed everywhere over the bulk [7], the -phase in the Fe 50 Cr 50 alloy is found in a thin surface layer only [5]. The -phase formation in the surface layer may be associated with the high elastic stresses that arose during the transformation of the bcc lattice of a Fe-Cr solid solution into a tetragonal lattice of the -phase.…”

“…It turns out that only the conventional light microscopy and the X-ray diffraction phase analysis have been used for this purpose (it is axiomatic that we are dealing with structural methods only). The resolution of these methods in relation to the high-dispersed particles present in a microstructure is quite low, so that TEM, when it began to be used, has led to a sudden detection of phenomena like modulated microstructures and microstructures formed as a result of a tendency towards phase separation [5][6][7][8][9][10][12][13][14][15][16][17][18][19][20][21]. We would like to emphasize that the references mentioned here, in which the highly dispersed phase separation microstructures have been found, belong to a very small part of systems having a region of solid solution in the corresponding phase diagram.…”

Phase separation in the Fe–Mn system

“…It has been shown that at 1200-1400 • C, a tweed microstructure is formed in the Fe-(20-30) wt.% Cr alloys; with increasing Cr content in the Fe-Cr alloys up to 40-47 wt.% other microstructures of phase separation are formed at the same temperatures: ␣ 1 + ␣ 2 microstructure, heavily enriched with Cr particles termed as a J-phase, and even particles having an A12 metastable lattice of Cr [5,6]. Microstructures of phase separation have been found also in the following systems: Fe-Ti [7], Fe-W [8], Fe-Co [9], Fe-V [10], using TEM, X-ray diffraction (XRD) and field-ion microscopy. Modulated microstructures which have been not considered as microstructures of phase separation at their detection have been observed after water-quenching from the high-temperature regions of a solid solution in the following systems: Au-Ni [11], Ni-Mo [12], Fe-Be [13], Al-Zn [14], Cu-Be [15], Nb-Zr [16].…”

“…they can be considered as a result of phase separation of the alloys at high temperatures. Since all the microstructures of phase separation [4][5][6][7][8][9][10] and the modulated ones [11][12][13][14][15][16] as well have been found after quenching in water from the region of a solid solution, the conclusion [19] has been made that in reality the regions of a solid solution in phase diagrams are regions, in which there is a tendency toward separation and, as a result, microstructures of phase separation are formed.…”