Microstructure evolution and thermal behavior of equimolar ultrafine-grained CuFe immiscible alloy

Microstructure evolution and thermal behavior of equimolar ultrafine-grained CuFe immiscible alloy

Článek WoS

Immiscible alloys, characterized by their positive enthalpy of mixing, offer unique opportunities to tailor material properties such as strength and thermal stability. This study investigates the microstructure and thermal behavior of an equimolar CuFe immiscible alloy prepared by a combination of mechanical alloying of elemental powders and sintering by the Spark Plasma Sintering method. Mechanical alloying enabled the mixing of mutually immiscible elements and the formation of metastable supersaturated solid solution. This solid solution decomposed into a dual-phase microstructure in the temperature range of 280 degrees C - 480 degrees C. Activation energy calculations indicated that the decomposition mechanism was a spinodal decomposition followed by phase growth. After sintering, an ultrafine-grained dual-phase microstructure consisting of Cu-rich and Fe-rich phases was formed. These phases showed varying levels of supersaturation, leading to the presence of some Fe-rich phases with an FCC crystal structure at room temperature. Moreover, this supersaturation led to a decrease in the BCC/FCC phase transformation temperature of the BCC Fe-rich phases by approximately 130 degrees C. During annealing at 980 degrees C, a partial decrease in the supersaturation of the phases occurred, which was reflected in an increase in the amount of BCC Fe-rich phases. However, the temperature shift of the BCC/FCC phase transformation was retained. The grain size after annealing increased from 0.49 mu m to 0.67 mu m, which can be described as excellent thermal stability considering the high annealing temperature (90 % of the melting temperature). This exceptional thermal stability stems from the immiscible nature of the alloy, which hinders grain growth.

Immiscible alloys, characterized by their positive enthalpy of mixing, offer unique opportunities to tailor material properties such as strength and thermal stability. This study investigates the microstructure and thermal behavior of an equimolar CuFe immiscible alloy prepared by a combination of mechanical alloying of elemental powders and sintering by the Spark Plasma Sintering method. Mechanical alloying enabled the mixing of mutually immiscible elements and the formation of metastable supersaturated solid solution. This solid solution decomposed into a dual-phase microstructure in the temperature range of 280 degrees C - 480 degrees C. Activation energy calculations indicated that the decomposition mechanism was a spinodal decomposition followed by phase growth. After sintering, an ultrafine-grained dual-phase microstructure consisting of Cu-rich and Fe-rich phases was formed. These phases showed varying levels of supersaturation, leading to the presence of some Fe-rich phases with an FCC crystal structure at room temperature. Moreover, this supersaturation led to a decrease in the BCC/FCC phase transformation temperature of the BCC Fe-rich phases by approximately 130 degrees C. During annealing at 980 degrees C, a partial decrease in the supersaturation of the phases occurred, which was reflected in an increase in the amount of BCC Fe-rich phases. However, the temperature shift of the BCC/FCC phase transformation was retained. The grain size after annealing increased from 0.49 mu m to 0.67 mu m, which can be described as excellent thermal stability considering the high annealing temperature (90 % of the melting temperature). This exceptional thermal stability stems from the immiscible nature of the alloy, which hinders grain growth.

Immiscible alloys, Spinodal decomposition, Thermal analysis, Mechanical alloying, Thermal stability

Immiscible alloys, Spinodal decomposition, Thermal analysis, Mechanical alloying, Thermal stability

ADAM, O.; SPOTZ, Z.; ČUPERA, J.; POUCHLÝ, V.; JAN, V.

23.09.2025

Journal of Alloys and Compounds

1040

Švýcarská konfederace

183183

11

https://www.sciencedirect.com/science/article/pii/S0925838825047449