Internal stress-induced melting below melting temperature at high-rate laser heating

Abstract

In this Letter, continuum thermodynamic and phase field approaches (PFAs) predicted internal stress-induced reduction in melting temperature for laser-irradiated heating of a nanolayer. Internal stresses appear due to thermal strain under constrained conditions and completely relax during melting, producing an additional thermodynamic driving force for melting. Thermodynamic melting temperature for Al reduces from 933.67 K for a stress-free condition down to 898.1 K for uniaxial strain and to 920.8 K for plane strain. Our PFA simulations demonstrated barrierless surface-induced melt nucleation below these temperatures and propagation of two solid-melt interfaces toward each other at the temperatures very close to the corresponding predicted thermodynamic equilibrium temperatures for the heating rate Q≤1.51×1010K/s. At higher heating rates, kinetic superheating competes with a reduction in melting temperature and melting under uniaxial strain occurs at 902.1 K for Q = 1.51 × 1011 K/s and 936.9 K for Q = 1.46 × 1012 K/s.

A metastable liquid melted from a crystalline solid under decompression

“…1a). Apparently, the shear stress may have played an important role in lowering melting temperature of Bi-I, as reported in other materials2021222324. The use of liquid neon in this study provides excellent hydrostatic condition, thus revealing the true melting temperature higher than 489 K. Upon decompression at 489 K, Bi-IV melts into a liquid at ∼2.3 GPa, and crystallizes into Bi-I at ∼1.2 GPa under further decompression (Fig.…”

“…At least, one of them must be metastable. Interestingly, crystalline Bi-II (or II′) under compression at 489 and 482 K occurs above the reported T m of 464 K. Because shear stress could significantly lower melting temperature2021222324, the true melting temperature of Bi-II and Bi-II′ under hydrostatic condition may be higher than the reported 464 K. On the other hand, the lowest temperature where we observed the DIL is 441 K, far below the reported T m . It is then likely that the DIL could be metastable.…”

Comment on “In situ imaging of ultra-fast loss of nanostructure in nanoparticle aggregates” [J. Appl. Phys. 115, 084903 (2014)]

“…Then heterogeneous heating was modeled by prescribing a heating rate of 0.9 Â 10 11 K/s to the part of the Al surface at O 0 C. Melting was modeled using the phase-field approach coupled to mechanics. 7,8 Melting drastically increases heterogeneity of stresses ( Fig. 1(b)), which will lead to fracture of the shell near the sintered part well before the rest of the shell.…”

Multiphase phase field theory for temperature-induced phase transformations: Formulation and application to interfacial phases

“…In contrast, the thermodynamic instability was included in consideration in [1,2,8], which resulted in PT criteria. This allows one to consider problems at the actual physical space scale where thermodynamic instability is important, e.g., for very fast heating much higher than the melting and even solid instability temperatures [55,56], as well as for barrierless surface-induced melting, especially for nanoparticles [57,58], and for melting within an interface between two solids [24-26, 29, 31], which all may occur significantly below melting and melt instability temperatures. The interpolation function (18) that satisfies all conditions has been used for various applications for a long time [1,2,33,46,47,52,53].…”