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

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 (T(0)). Here we report quantitative experimental measurements on the ΔT(−)-ΔT(+) relationship of Al small particles encapsulated in Al(2)O(3) 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 T(0) of Al (~1.36T(0)), 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.