Dependence of Liquid Supercooling on Liquid Overheating Levels of Al Small Particles

Abstract

The liquid thermal history effect on liquid supercooling behavior has been found in various metals and alloys; typically the degree of liquid supercooling (ΔT−) increases with the increase of liquid overheating (ΔT+) up to several to tens of degrees above the equilibrium melting point (T0). Here we report quantitative experimental measurements on the ΔT−-ΔT+ relationship of Al small particles encapsulated in Al2O3 shells by using a differential scanning calorimeter. We find a remarkable dependence of ΔT− on ΔT+ of Al small particles, extending to at least 340 °C above T0 of Al (~1.36T0), which indicates the existence of temperature-dependent crystallization centers in liquid Al up to very high liquid overheating levels. Our results demonstrate quantitatively the significant effect of liquid thermal history on the supercooling behavior of Al and its alloys, and raise new considerations about the dependence of ΔT− on ΔT+ at very high ΔT+ levels.

Microstructural verification of the theoretically predicted morphologies of the NiAl–Cr pseudo-binary alloy systems and NiAl–Cr eutectic structure modification by Mo addition

“…As the melting temperature is raised, the overheating temperature is smaller and the respective undercooling lower. Similar conditions of overheating and corresponding undercooling have been reported by Mei et al [38] and Yang et al [39].…”

NiAl-Cr-Mo Medium Entropy Alloys: Microstructural Verification, Solidification Considerations, and Sliding Wear Response

“…Having taken into consideration the fact that during arc melting, the temperature of heating and melting of the various systems was kept constant (arc parameters were not modified or changed), it is logical to assume that the increase of the liquidus temperature corresponds to a lower degree of liquid phase overheating, compared with the case of the NiAl-40Cr alloy. A lower degree of liquid phase overheating, as Mei and Li [49] and Yang et al [50] postulate, leads to a reduction of the necessary for nucleation undercooling. In the case of the present work, this practically implies that the presence of Mo shifts the T0-A2 temperatures towards higher values, i.e., the necessary undercooling for primary Cr(Mo) A2 phase nucleation is reduced.…”