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

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 (T_x1= 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 T_x1, 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 T_x1, 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.