Effect of Al doping on the magnetic and elastic properties of Fe65Ni35 Invar alloys

Invar alloys have great importance due to their low thermal expansion coefficient. The effect of Al doping on Fe65Ni35 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 Fe65Ni35 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 Fe65Ni35 Invar alloy led to volume shrinkage and decreasing Curie temperature as seen in the effect of hydrostatic pressure application.