Thermal transport property correlated with microstructural evolution of Fe-based amorphous alloy

Abstract The correlation between the thermal transport properties and microstructural evolution of amorphous alloys is crucial for their application in thermal insulation. Herein, Fe48Cr15Mo14C15B6Y2 amorphous alloy with low thermal conductivity of 7.74 W/mK was investigated to reveal this relationship. Isochronal annealing experiment demonstrates a limited increase in thermal conductivity at temperatures below the crystallization temperature (Tx1= 620.7 °C), despite the occurrence of structural relaxation or partial crystallization, which is ascribed to the conflicting variations of electron and phonon contributions with increasing temperature. At annealing temperature above Tx1, the two contributors start to cooperate, leading to abrupt enhancement of thermal conductivity. On the other hand, isothermal annealing experiments reveal that at temperatures below Tx1, the thermal conductivity is independent of annealing time. Although full crystallization can be induced slowly by annealing at 600 °C, the thermal conductivity keeps nearly constant at 8.35 W/mK, which is attributed to additional scattering by a newly introduced phase interface. Moreover, grain growth upon prolonged annealing at 850 °C results in a slow increase in thermal conductivity, which asymptotically saturates at 12.44 W/mK. The obtained results demonstrate the potential of the Fe-based amorphous alloy as thermal insulator and form a basis for future works aiming to shed further light on the evolution of amorphous alloy and the sluggish effect of transformation kinetics.