Enhancement of Microhardness in FINEMET Alloy Due to Heat Treatment.

Abstract

This study investigates the effect of heat treatment on the structural, magnetic, and mechanical properties of the FINEMET alloy with composition Fe73.5Cu1Nb3Si13.5B9. The alloy was synthesized using the melt spinning technique and subsequently annealed at temperatures ranging from 400℃ to 600℃. The primary objective of this research is to optimize the properties of the alloy for potential use in energy-efficient applications, particularly in magnetic sensors and electromagnetic wave absorbers. Structural characterization was performed using X-ray diffraction (XRD), which revealed the development of well-defined crystalline phases after heat treatment. The results further indicate a significant refinement of grain size, decreasing from approximately 125.3 nm in the as-prepared sample to about 39 nm after annealing. Magnetic properties were analyzed through magnetic hysteresis (M–H) measurements using a vibrating sample magnetometer. The findings demonstrate that both magnetic saturation and coercivity decrease with increasing annealing temperature, resulting in enhanced magnetic softness of the alloy. Additionally, microhardness measurements show a linear increase with heat treatment, which correlates with the reduction in grain size and coercivity. The combined improvement in magnetic and mechanical properties indicates that heat treatment plays a crucial role in tailoring the performance of this FINEMET alloy. Among the studied samples, the alloy annealed at 600℃ exhibits the most favorable combination of magnetic softness and increased microhardness, making it a promising candidate for practical technological applications.