Inverse melting in the Ti-Cr system

Thermodynamics and kinetics of the Mg65Cu25Y10 bulk metallic glass forming liquid

“…The case of a supercooled liquid having a lower entropy than a crystal was observed previously during ''inverse melting'' in Cr-Ti and similar systems. 22,23 In these cases the crystalline phase was a metastable bcc solid solution.…”

<i>In Situ</i> TEM Observation of Structural Changes in Rapidly Solidified bcc Solid-Solution Phase in Ti&ndash;Cr Alloy Focusing on Spontaneous Vitrification (SV)

“…3(a). It is noteworthy that Kim et al 17) and Yan et al 18) provided the BF images of an amorphous phase formed through SV and that their BF images did not exhibit the featureless contrast typical of an amorphous phase but rather a fine black-white contrast similar to the BF images shown in Figs. 3(c) and 3(d). These results imply that the previously reported SV may not correspond to the formation of an amorphous phase but to the formation of a finely grained crystalline structure composed of the hcp solid-solution phase and the Cr 2 Ti compound that had transformed from the bcc solid-solution phase.…”

“…The annealing temperature was fixed at 873 K on the basis of the results of the above thermal analysis and of previous reports. The formation of an amorphous phase through SV was previously reported for Ti 60 Cr 40 thin film annealed at 873 K, 1) for water-quenched Ti 60 Cr 40 alloy annealed at 873 K for 1.8 © 10 4 s, 2) for mechanically alloyed Ti 60 Cr 40 (obtained from an elemental powder blend of Ti 60 Cr 40 ) annealed at 823 K for 1.2 © 10 3 s, 17) and for mechanically alloyed Ti 50 Cr 50 annealed at 850 K for 1.8 © 10 3 s, 18) indicating that ex situ annealing at 873 K for a period on the order of 10 4 s was a suitable condition for the current experiment to determine whether SV actually occurs. The changes in the microstructure of the alloy were investigated using XRD and TEM, where the alloy was ex situ annealed at 873 K for various periods, and the results are shown in Fig.…”

“…Blatter et al, 4) Kim et al, 17) and Yan et al 18) previously reported that an amorphous phase had formed through SV of the bcc solid-solution phase on the basis of the SAD and XRD patterns they obtained. Fig.…”

“…Several researchers have conducted experiments to determine whether or not SV actually occurs. Although Kim et al 17) and Yan et al 18) reported that SV had occurred, Prasad et al, 19) Sinkler et al, 20) and Hirata et al 21,22) reported that it had not. Ranganathan and Ramachandra have recently suggested a new thermodynamic model for SV, 23) while Prasad and Greer concluded that SV was thermodynamically impossible.…”