Effect of Al doping on the magnetic and elastic properties of Fe₆₅ Ni₃₅ Invar alloys

Authors: ASLI ÇAKIR

Abstract: Invar alloys have great importance due to their low thermal expansion coefficient. The effect of Al doping on Fe₆₅ Ni₃₅ Invar alloy was investigated by temperature-dependent magnetization and elastic modulus measurements. First, 0.44 at% and 2.24 at% of Al were substituted for Ni. Then X-ray diffraction measurements, Rietveld refinements, and scanning electron microscopy studies were performed to understand the effect of Al-doping on the face-centered cubic structure. The elastic modulus of Fe₆₅ Ni₃₅ and the Al-doped samples were measured in the temperature range 300 ≤ T ≤ 870 K using impulse excitation. The temperature dependence of magnetization and elastic modulus results for the Al-doped Invar alloys were compared with those of nondoped Invar alloy. Al doping to Fe₆₅ Ni₃₅ Invar alloy led to volume shrinkage and decreasing Curie temperature as seen in the effect of hydrostatic pressure application.

Keywords: Invar alloy, elastic modulus, magnetization, structural characterization

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