Vitrification decoupling from α-relaxation in a metallic glass

Abstract

Understanding how glasses form, the so-called vitrification, remains a major challenge in materials science. Here, we study vitrification kinetics, in terms of the limiting fictive temperature, and atomic mobility related to the α-relaxation of an Au-based bulk metallic glass former by fast scanning calorimetry. We show that the time scale of the α-relaxation exhibits super-Arrhenius temperature dependence typical of fragile liquids. In contrast, vitrification kinetics displays milder temperature dependence at moderate undercooling, and thereby, vitrification takes place at temperatures lower than those associated to the α-relaxation. This finding challenges the paradigmatic view based on a one-to-one correlation between vitrification, leading to the glass transition, and the α-relaxation. We provide arguments that at moderate to deep undercooling, other atomic motions, which are not involved in the α-relaxation and that originate from the heterogeneous dynamics in metallic glasses, contribute to vitrification. Implications from the viewpoint of glasses fundamental properties are discussed.

Fragility of short‐chain poly(lactic acid)s derivatives by combining dielectric spectroscopy and fast scanning calorimetry

“…8 FSC, fast scanning calorimetry; MT-DSC, modulated temperature differential scanning calorimetry questioned since a decoupling between vitrification and molecular mobility has recently been evidenced. 18,19 Nevertheless, as can be seen in Figure 6, the dielectric and calorimetric data superimpose well in the present study. In consistence with previous studies, 5 the PDLLA exhibits a fragile behavior (m = 155), while the oligomers exhibit lower m, which decreases from 99 (OLA2700) down to 68 (OLA1400) with the M w decrease.…”

“…The MT‐DSC results are also added. It is worth mentioning that the validity of this approach can be questioned since a decoupling between vitrification and molecular mobility has recently been evidenced 18,19 . Nevertheless, as can be seen in Figure 6, the dielectric and calorimetric data superimpose well in the present study.…”

Experimental evidence of mosaic structure in strongly supercooled molecular liquids

“…From the glass-transition perspective, it is becoming more and more clear that the vitrification kinetics is not only driven by the structural relaxation, as traditionally believed, but other, faster processes must play a role to reduce the effectiveness of the structural relaxation to lock the atomic dynamics 3 . This is consistent with recent theoretical and numerical work pointing out that the free energy landscape relevant for the glassy state is much rougher than classically thought, with intra-state barriers associated with secondary relaxations 4 .…”

Phase Selection in Mn–Si Alloys by Fast Solid‐State Reaction with Enhanced Skyrmion Stability

“…This approach also works well for amorphous Au‐based and Pt‐based alloys. [ 29,30 ] Therefore, we anticipate that a fast annealing method, such as flash‐lamp annealing (FLA), [ 31 ] provides an effective way to separate B20‐MnSi and MnSi 1.7 and to control the ratio between both phases. During FLA, the sample is exposed to xenon flash lamps, such that the total energy budget is low, leading to a fast heating and cooling rate.…”